Obstructive Liver Injury and Oxidative Stress: From Pathogenesis to Therapeutic Perspectives

1. Introduction

Liver is the most commonly injured intra-abdominal organ with an incidence of 30%–40%. The overwhelming majority of liver injuries, however, are minor, with spontaneous cessation.[1] The liver is more often frequently affected by toxic injury more often than any other organ,which is unsurprising given that blood from the portal vein, draining the absorptive surfaces of the intestinal tract flows directly into it. Consequently the liver, thereby exposing it all ingested substances that are absorbed into the portal blood.[2] Contemporary advance in food safety and chemical hazard management have reduced liver injury from these sources. Liver injury can be classified by organ system count. Some classifications are based on the type of histopathological lesion (e.g inflammation, necrosis, cholestasis), while others focus on the type of injury (e.g., cytotoxic, cholestatic, mixed). Recent advance have provided new perspective on mechanism of injury. at the molecular level has given rise to a more focused scheme for evaluating and categorizing hepatic injury.Obstruction of the common bile duct in a various clinical manifestation may lead to cholestatic liver injury. [3,4]. Hepatic inflammation constituent an important aspect of this injury with neutrophils playing a predominant role.

The common bile duct may become obstructed in range of clinical condition, consisting of sclerosing cholangitis, cholangiocarcinoma, gallstone impaction and extrinsic compression caused by tumor or lymphadenopathy.complete biliary obstruction triggers cholestatic liver injury, marked by hepatocellular necrosis and apoptosis, proliferation of bile duct epithelial cells, activation of stellate cells activation, and, ultimately liver fibrosis, or lymphadenopathy.[5] one widely used experimental model for studying extrahepatic cholestatis is bile duct ligation [BDL] in rodent.cholestatis can result from medication,naturally occurring substances such as estrogens,or,in more severe cases,physical bloackage of the bile duct due to gallostones or tumors of the pancreas.initial research using rodent liver cell suggested that liver damage cholestatis primarily stems resulting from direct toxic effects of hydrophobic bile acids, which trigger oxidative stress in mitochondria and lead to programmed cell death.

However,this hypothesis has been challenged in the case of rodent hepatocytes,as studies have found from the direct toxic effects of hydrophobic bile acids,including glycochenodeoxycholic acid and related compounds stay several orders of magnitude below concentration that are known to induce cytotoxic effects.[6]. In contrast to other species ,the main site where assessment of glutathione disulfide efflux into bile shown an exceptionally high resistance of the liver to intracellular reactive oxygen generation (even when systems were impaired).[7] Nevertheless,under pathophysiological circumstances those involving metabolic disturbances, bile duct obstruction or ischemia the equilibrium between free radical production and the body’s ability to neutraliuze them may be diseupted. this imbalance can lead to oxidative stress,which in turn may impair cellular homeostatis and the normal functioning of organelles.

2. Pathophysiology of Obstructive Liver Injury

2.1. Cholelithiasis (Gallstones)

Gallstones constitute the most prevalent cause of extrahepatic biliary obstruction in Western populations, affecting approximately 10–15% of adults.[8] Cholesterol gallstones form as a consequence of bile supersaturation, nucleation, and crystal growth, whereas pigment stones arise from excess unconjugated bilirubin or infection-related biliary stasis. Common bile duct stones (choledocholithiasis) obstruct bile outflow and are associated with acute obstructive jaundice cholangitis and secondary biliary cirrhosis if untrated.[9]

2.2. Biliary and Periampullary Tumors

Pancreatic head adenocarcinoma, cholangiocarcinoma, and ampullary carcinoma collectively represent the principal malignant causes of biliary obstruction.[10] Cholangiocarcinoma, arising from bile duct epithelium, may be intrahepatic, perihilar or distal in location, and is frequently associated with primary sclerosing cholangitis. The progressive nature of malignant obstruction tends to produce prolonged and severe cholestasis with substantial hepatocellular compromise.[11]

2.3. Biliary Strictures

Benign biliary strictures may result from iatrogenic injury during cholecystectomy, chronic pancreatitis, anastomotic stricture following hepatobiliary surgery, or inflammatory conditions such as primary sclerosing cholangitis (PSC).[12] PSC is a chronic cholestatic liver disease characterized by progressive fibro-inflammatory destruction of both intrahepatic and extrahepatic bile ducts, with a significant proportion of patients progressing to cirrhosis and liver failure.[13]

2.4. Congenital Abnormalities

Biliary atresia,characterized by a fibroimflammatory blockage of the extrahepatic bile duct in newborns,is the most frequent surgical cause of neonatal cholestatis and primary reason for liver transplantation in children.[14] other condition contributing to cholestatic liver diasease inclide choledochal cysts, Alagille syndrome,and various forms of intrahepatic cholestatis.These disorders reflect different etiologies based on the specific location of injury within the hepatobiliary system. Bile production is a multifaceted process carry out by hepatocytes and cholangiocytes,with a bile acid transporters working in concert with specific cell surface receptors on cholangiocytes that to control their secretory activity and function.Histologic overview of cholestatic liver disease shows bland hepatic cholestasis in drug induced injury, the small bile duct lymphocytic cholangitis of primary biliary cholengitis [PBC], ductopenia as demonstrated by keratin immunostaining,the typical large bile duct lesions observed in primary sclerosing cholangitis[PSC] known as obliterative cholangitis, and immunochemical staining revealing IgG4-positive plasma cells surrounding a bile duct IgG[15,16]

2.5. Mechanisms of Hepatocellular Injury in Cholestasis

Cholangiocytes are ethical cell that line the bile duct,they represent 3-5 % of cell type in liver bile is product of transport and secreation of bile acid, phospholipid,bilirubin,cholesterol,electrolyte protein,endo and xenobiotic detoxification product and water by hepatocytes to greter extent but cholangiocyte play vital role in bile formation. Several small molecule compound ligands have been identified for key target involved in regulating bile acid metabolism,offering a promising pathway for developing new cholestatis treatment and improving therapeutic option for affected patients.[18] Among these the FXR agonist obeticholic acid has shown notable effectiveness in alleviating symptoms and enhancing liver function in cholestatic patient who remain non-responsive to ursodeoxycholic acid[UDCA].The recruitment and activation of hepatic macrophages (Kupffer cells) initiates a pro-inflammatory response characterized by the release of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6), which further amplify oxidative injury.[19] Third, neutrophil infiltration, driven by bile acid-stimulated hepatocyte enhanced production of adhesion molecules and chemokines, contributes to oxidant-mediated tissue destruction.[20] Activation of hepatic stellate cells (HSCs) by oxidative stress, pro-inflammatory cytokines, and transforming growth factor-beta (TGF-β) drives the transition of quiescent stellate cells to a myofibroblastic phenotype, the primary cellular mediator of hepatic fibrogenesis.[21]The resultant excess deposition of extracellular matrix proteins, particularly type I collagen, progressively disrupts hepatic architecture, ultimately leading to cirrhosis and portal hypertension[22,23]

3. Oxidative Stress: Basic Concepts and Hepatic Sources

3.1. Defination and Conceptual Framework

Sies initially characterised oxidative stress in 1985 as a disruptive of the balance between prooxidant and antioxidant toward a prooxidant state. [24] The concept has since evolved to encompass not only oxidative damage to macromolecules but also the disruption of redox signaling and control.

Reactive oxygen species such as superoxide anion (O₂•⁻), hydrogen peroxide (H₂O₂), and the highly reactive hydroxyl radical (OH), are present along characterized by the generation of reactive oxygen species,particularly nitric oxide[NO] and peroxynitrite. [25]

Under normal physiological conditions, low concentration of reactive oxygen species [ROS] act as signaling molecule in cellular pathway that control processes such as cell growth,specialization and immune function.However,when ROS generation overwhelms the body’s antioxidants defenses, a state of pathological oxidative stress develops. This imbalance leads to widespreads and ongoing oxidative damage affecting lipids,protein,and genetic material.[26]

3.2. Hepatic Sources of Reactive Oxygen Species

3.2.1. Mitochondria

Mitochondria are the predominant intracellular source of ROS in hepatocytes, generating superoxide predominantly at complexes I and III of the mitochondrial electron transport chain. Under cholestatic conditions, bile acid-induced mitochondrial permeability transition (MPT) markedly increases electron leak,originating within mitochondrial electron transport system, amplifying superoxide and H₂O₂ production. Glycochenodeoxycholic acid (GCDCA) and other conjugated bile acids have been shown to induce MPT in isolated rat liver mitochondria in a concentration-dependent manner .[27]

3.2.2. Kupffer Cells and NADPH Oxidase

Kupffer cells, the resident macrophages of the liver, represent a critical source of ROS in inflammatory hepatic injury. Upon activation by pathogen-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs), or bile acids, Kupffer cells generate superoxide through the NADPH oxidase (NOX) compound. The NOX2 isoform is particularly important in Kupffer cell-mediated oxidative burst, which contributes to sterile inflammatory hepatocellular injury in cholestasis.[28]

3.2.3. Cytochrome P450 System

The microsomal cytochrome P450 (CYP) enzyme system, particularly CYP2E1, is a well-recognized source of hepatic ROS. CYP2E1 catalyzes the oxidative metabolism of numerous substrates with a high rate of uncoupling, producing superoxide and H₂O₂ as byproducts [29]. In cholestatic liver disease, CYP-mediated ROS generation is exacerbated by substrate accumulation and enzyme induction, contributing meaningfully to total oxidative load.[30

3.3. Antioxidant Defense Systems

3.3.1. Enzymatic Antioxidants Defence System

The liver possesses a sophisticated enzymatic antioxidant arsenal. Superoxide dismutase (SOD), existing as cytosolic Cu/Zn-SOD (SOD1) and mitochondrial Mn-SOD (SOD2), catalyzes the dismutation of superoxide to H₂O₂ and molecular oxygen.[31]

Catalase, primarily localized in peroxisomes,break down hydrogen peroxide into water and oxygen.The glutathione peroxidase (GPx)enzyme family help reduce hydrogen peroxide and lipid hydroperoxides through glutathione(GSH) dependent reduction as the electron donor, a reaction coupled to glutathione reductase (GR)-dependent regeneration of GSH from GSSG.[32]

3.3.2. Non-Enzymatic Antioxidants Defence Systems

Non-enzymatic antioxidants contribute to the overall antioxidant defence system,against oxidative injury, Reduced glutathione (GSH), the predominant intracellular antioxidant.the most abundant intracellular thiol, serves as a cofactor for enzymatic antioxidants and directly scavenges ROS and electrophiles. Vitamin E (α-tocopherol) is the principal lipid-soluble chain-breaking antioxidant, preventing propagation of membrane lipid peroxidation.[33]

Vitamin C (ascorbic acid) functions as a water-soluble radical scavenger and regenerates vitamin E from its radical form. Additional non-enzymatic antioxidants include uric acid, bilirubin at physiological concentrations, coenzyme Q10, and dietary polyphenols [34]

4. Interplay Between Obstructive Liver Injury and Oxidative Stress

4.1. Role of Bile Acids in ROS Generation

Bile acid induced ros generation in isolated hepatic mitochondria and other that bile acid can generate RosThe drug as well as cell leaking mitochondria function,when incable of stimulating ROS level after exposure to ionising radiation. Thus bile acid could activating ERBB1 in hepatocytes in similar to ionising radiation,in tumor cell by causing generation of ROS.[35,36]

Cell can produce reactive oxygen species[ROS] that may either promote or inhibit apoptosis,depending on the type of stimulus and the level and duration of ROS production.In liver bile acid concentration are known to vary in response to various agent our in vitro finding suggest that these fluctuation might also influence ROS level.when bile acid are released and subsequently reabsorbed along with nutrients, the resulting ROS could play a role in regulating liver metabolism of glucose and lipid potentially by affecting AKT/glycogen synthase activity and the stability ERK1/2/LDL receptor mRNA.Affecting cholestatic liver disease,sustained exposure to high concentrations of bile acids level lead to cause oxidative stress which impair signaling pathways like PI3WAKT,ultimately disrupting glycogen synthase regulation.[38]

4.2. Mitochondrial Dysfunction

Metabolic disturbances in cholestatic liver injury are also worsened by the infiltration of inflammatory cells,the release of pro-apototic factors,and subsequent cell death. Mitochondria are central to this process, serving as a link between inflammation, apoptosis and energy metabolism are linked; however, mitochondrial damage is not adequately offset by sufficient mitochondrial biogenesis which limits functional recovery and impairs mitochondrial.[39] These damage mitochondria become major significant sources of reactive oxygen species (ROS), which in turn can then promote the onset of apoptosis and are also contribute to activation of pro-fibrogenic mechanisms. Additionally,impaired mitochondrial function in the liver is associated with an increase glycolytic activity to meet energy demand. The buildup of bile acids impaired mitochondrial function and energy production by directly reducing the activity of enzyme complexes in the electron transport chain. In the early phage of cholestasis, a certain degree of resistance to cell death may develop.[40] During this phase, elevated cardiolipin levels in the mitochondria alter the mitochondrial membrane composition,reducing the likehood of MPT pore formation, and raising the threshold for apoptosis. Under normal conditions Mitochondrial ROS trigger signaling pathways but when present but in excess they induce oxidative stress and oxidative damage. Bile acids such as DCA and taurodeoxycholic acid [TDCA] enhance mitochondrial ROS generation in hepatocytes. Mitochondrial ROS can also inactive protein tyrosine phosphatases (PTPase), leading to phosphorylation of the epidermal growth factor receptor ERBB1 and subsequent activation of MEK1/2 and ERK1/2. [41,42]

4.3. Inflammatory Cascade and Kupffer Cell Activation

Kupffer cells are tissue-resident macrophages located in the liver tissue. They have a strong phagocytic ability, which allows them to remove foreign substances such as viruses and bacteria,as well as apoptotic cells and cellular debris. This function is essential for Kupffer cells because they serve as a gatekeeper in the innate immune response. [43] Kupffer cells are present in the hepatic sinusoids and are can move along the hepatic sinusoidal endothelial cells, which enables them to effectively clear foreign pathogens that enter the liver via the portal venous system. Efficiently neutrophil-derived myeloperoxidase (MPO) catalyzes the generation of hypochlorous acid (HOCl) from H₂O₂ and chloride, a potent oxidant with broad cytotoxic activity.Inducible nitric oxide synthase (iNOS) upregulated in activated macrophages generates NO, which reacts with superoxide to form peroxynitrite (ONOO⁻), a powerful nitrating and oxidizing agent that can trigger protein tyrosine nitration and lipid peroxidation.[44]

4.4. Lipid Peroxidation and Membrane Damage

Lipid peroxidation, initiated by ROS-mediated abstraction of hydrogen atoms from polyunsaturated fatty acids (PUFAs) in cellular membranes, represents among the most destructive consequences driven by oxidative stress.[45] The generated lipid radical chain reaction generates a cascade of reactive aldehydic products including MDA, 4-hydroxynonenal (4-HNE), and acrolein, which form covalent adducts with proteins, phospholipids, and DNA bases 4-HNE is of particular pathological significance in cholestatic liver injury, as it activates TGF-β- mediated profibrotic signaling in hepatic stellate cells, stimulates collagen synthesis, and serves as a potent inducer of fibrogenesis.[46] Hepatocellular membrane disruption by lipid peroxidation also compromises bile acid transport protein function, including NTCP (sodium-taurocholate cotransporting polypeptide) and BSEP (bile salt export pump), exacerbating intracellular bile acid retention and perpetuating the oxidative cycle.[47]

5. Molecular Mechanisms and Signaling Pathway

5.1. NF-κB Pathway

Nuclear factor-kappa B (NF-κB) represents a master transcriptional regulator of inflammatory and oxidative stress responses in hepatic cells.Under basal conditions, NF-κB is sequestered in the cytoplasm bound to inhibitory IκB proteins. Bile acids, ROS, and pro-inflammatory cytokines activate IκB kinase (IKK), leading to phosphorylation and proteasomal degradation of IκB, nuclear translocation of the NF-κB p65/p50 heterodimer, and transcriptional activation of target genes including TNF-α, IL-1β, IL-6, cyclooxygenase-2 (COX-2), and iNOS.[48] Paradoxically, NF-κB also induces the expression of anti-apoptotic genes (Bcl-2, Bcl-xL, IAP family members) and antioxidant enzymes (SOD2, HO-1), representing an intrinsic hepatoprotective counter-regulation [49]. The net outcome of NF-κB activation in obstructive liver injury thus depends on the balance between its pro-inflammatory and cytoprotective transcriptional programs, a balance influenced by disease stage, severity, and the specific cellular context [50]

5.2. Nrf2 Pathway

Nuclear factor erythroid 2-related factor 2 (Nrf2) serves as the primary transcriptional activator of the cellular antioxidant response.Under basal condition, Nrf2 is held in the cytoplasm by its inhibitor Kelch-like ECH-associated protein 1 (Keap1), which facilitates constitutive Nrf2 ubiquitination and proteasomal degradation.Oxidative stress and electrophilic compounds modify critical cysteine residues on Keap1, disrupting Nrf2 ubiquitination, permitting its nuclear translocation, and enabling binding to antioxidant response elements (AREs) in the promoters of cytoprotective genes.[51]Nrf2 target genes encode a comprehensive antioxidant and detoxification program, including NQO1 (NADPH:quinone oxidoreductase, heme oxygenase-1 (HO-1), glutathione S-transferases, thioredoxin reductase, and glutamate-cysteine ligase[GCL],which is the rate-limiting enzyme for GSH synthesis [52]. In experimental BDL models, Nrf2 activation is initially upregulated as an adaptive response but is progressively overwhelmed in advanced cholestasis, contributing to antioxidant depletion and injury propagation [53]. Nrf2-null mice subjected to BDL exhibit markedly exacerbated oxidative injury and fibrosis compared to wild-type controls, underscoring the pathway's hepatoprotective importance.[54]

5.3. MAPK Pathway

Mitogen activated protein kinase phosphatase 5 (MKP5) belong to the MKP family and has been linked to a range of biological and pathological processes. However, the role of MKP5 in liver injury remain unclear.[55] liver injury influence by multiple factors, such as metabolism overload, mitochondrial damage, oxidative stress, apoptosis,and immune cell activation.Furthermore during liver injury, multiple signaling pathways undergo changes and activation of the mitogen-activated protein kinase (MAPK) is particularly important. Decreasing MAPK pathway activation can significantly reduce liver ischemia-reperfusion injury 16–20. Therefore, finding methods to control MAPK signaling has emerging as a major priority in the treatment of liver I/R injury. MAPK are part of the MAPK phosphatase (MKP) family.[56] Conversely, ERK1/2 activation can mediate both proliferative and apoptotic responses depending on the cellular context and duration of activation. p38 MAPK, mediated by oxidative stress and inflammatory cytokines, coordinates the hepatic acute-phase response and regulates bile acid metabolism gene expression through phosphorylation of hepatocyte nuclear factor 4α (HNF4α).[57]

5.4. Apoptosis and Necrosis

Hepatocyte death in obstructive liver injury occurs through both apoptotic and necrotic cell death pathway, with the relative contribution of each depending on the severity and duration of the oxidative insult.[58] Bile acid-induced apoptosis is primarily mediated through the intrinsic (mitochondrial) pathway, involving Bax translocation to the outer mitochondrial membrane, cytochrome c release into the cytoplasm, and activation of the caspase-9/caspase-3 cascade. Death receptor-mediated (extrinsic) apoptosis via Fas/FasL and TRAIL/DR5 pathways also contributes to bile acid-induced hepatocyte death.[59] Necrosis, characterized by cellular swelling, membrane rupture, and release of pro-inflammatory intracellular contents, predominates when ATP depletion exceeds a critical threshold, precluding the energy-dependent execution of apoptosis.Necroptosis a regulated, receptor-interacting protein kinase (RIPK)3-dependent form of necrotic cell death has more recently been implicated in cholestatic liver injury, offering potential therapeutic targets for intervention.[60]

6. Experimental Models of Obstructive Liver Injury

6.1. Bile Duct Ligation Model

The surgical bile duct ligation (BDL) model in rodents primarily including rats and mice,represents the most widely utilized and extensively validated experimental paradigm for obstructive cholestatic liver injury. [61] Following ligation and division of the common bile duct, animals develop progressive conjugated hyperbilirubinemia, elevation of serum alkaline phosphatase and gamma-glutamyltransferase, and histological evidence of bile duct proliferation, periportal inflammation, and hepatocellular necrosis within 3–7 days.[62] Oxidative stress parameters in the BDL model demonstrate consistent and reproducible changes: hepatic MDA levels rise approximately 2–4 fold within 7 days, accompanied by significant depletion of GSH (40–60% reduction), diminished activities of SOD, catalase, and GPx, and with concomitant upregulation of HO-1 and Nrf2 as adaptive responses.[63] The BDL model has proven invaluable for testing antioxidant and anti-fibrotic therapeutic interventions, with the caveat that the complete mechanical obstruction may not fully recapitulate the partial or progressive obstruction characteristic of human biliary diseases. [64]

6.2. In Vitro Models

Primary rat and human hepatocytes, as well as hepatocyte-derived cell lines (HepG2, HepaRG, Huh7), treated with hydrophobic bile acids (GCDCA, CDCA, DCA) at supraphysiological concentrations recapitulate key aspects of cholestatic hepatocyte injury in vitro.[65,66]

6.3. Genetic Mouse Models

Gene-targeted mouse models have provided important mechanistic insights into cholestasis-associated oxidative stress. Mdr2-knockout (Abcb4) mice, lacking the phosphatidylcholine floppase critical for biliary phospholipid secretion, develop spontaneous sclerosing cholangitis and serve as a model of inflammatory cholistatis liver disease. [67] FXR-null mice exhibit dysregulated bile acid metabolism and enhanced cholestatic susceptibility.Conversely, Nrf2-knockout mice demonstrate exaggerated oxidative injury and fibrosis in BDL and other hepatotoxic models, while Keap1-hypomorphic (Nrf2-hyperactivated) mice are relatively protected.[68]

6.4. Surgery-Induced Rodent Models

The most frequently used surgically induced animal model for cholestasis relies on bile duct ligation (BDL), where a ligature is placed or surgical ligation is performed on the common bile duct. This surgical procedure causes an extrahepatic obstruction of the biliary system, leading to cholestasis and inflammation. The BDL model creates acute extrahepatic obstructive biliary lesions, reflecting the clinical situation of gallstone liver disease and biliary atresia. However,although BDL is strictly an extrahepatic obstruction, the model has also been used as a platform to explore the subsequent functional pathophysiological processes in function resulting from obstructive cholestasis. Thus the BDL model has therefore also been extensively utilized to study PSC.Initially developed for rats,which lack a gallbladder,it was successfully adapted for mice. BDL in mice lead to jaundice, release of transaminases, elevated serum billirubin levels, along with bile duct proliferation and leukocyte infiltration, which ultimately leads to liver fibrosis. In contrast to rats and humans, mice show a biliary type of hepatocytic necrosis (bile infarcts) rather than apoptosis. [69,70]

7. Clinical Implication

7.1. Disease Progression and Complications

The clinical trajectory of unresolved obstructive liver injury follows a pathologically defined sequence from initial hepatocellular injury through fibrosis, cirrhosis, and hepatic fibrosis characterised by extensive extracellular matrix[ECM] accumulation, predominantly in the periportal and pericanalicular zones in cholestatic disease, progresses through stages F1–F4 on the METAVIR scoring system, with F4 representing established cirrhosis.[72] progression to cirrhosis in chronic cholestatic liver disorders,including primary biliary cholangitis(PBC) and PSC, is associated with portal hypertension, variceal hemorrhage, ascites, spontaneous bacterial peritonitis, hepatic encephalopathy, and hepatocellular carcinoma (HCC).[73] Oxidative stress-driven HCC development in cholestatic liver disease involves ROS-mediated mutagenic DNA damage, epigenetic alterations, and oxidative activation of carcinogenic signaling pathways including Wnt/β-catenin and PI3K/Akt/mTOR. [74]

7.2. Biochemical Biomarkers

Serum aminotransferases (ALT, AST) are widely used clinical markers of hepatocellular injury but provide limited specificity for oxidative stress-mediated damage[75]. Serum level of alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT) serve as indicators of biliary epithelial damage and cholestasis, respectively, with GGT reflecting intracellular GSH metabolism and oxidative stress response.[76] Malondialdehyde (MDA), measured by the thiobarbituric acid reactive substances (TBARS) assay in serum or tissue, is the most widely employed oxidative stress biomarker in clinical hepatology research.[77] 8-isoprostane (8-iso-PGF2α), a non-enzymatic cyclooxygenation product of arachidonic acid, provides a more specific and reliable in vivo index of lipid peroxidation.Urinary and plasma 8-hydroxy-2'-deoxyguanosine (8-OHdG) serve as an biomarker of oxidative DNA damage and is elevated in both experimental and clinical cholestasis.

Blood and tissue glutathione (GSH/GSSG ratio), SOD activity, catalase activity, and total antioxidant capacity (TAC) assays provide complementary assessments of the antioxidant defense status.Advanced glycation end-products (AGEs) and protein carbonylation, assessed by oxyblot analysis, serve as markers of protein oxidative damage in advanced hepatic disease.[78]

8. Therapeutic Approaches

8.1. Antioxidant Therapy

8.1.1. N-Acetylcysteine (NAC)

N-acetylcysteine, a thiol-containing compound that serves as a GSH precursor and direct ROS scavenger, has been among the most extensively studied hepatoprotective antioxidants.By replenishing intracellular GSH, NAC restores enzymatic antioxidant capacity and protects against bile acid-induced mitochondrial oxidative damage.The liver is an organ that is vulnerable oxidative damage and inflammation and given the significance of NAC as an antioxidant in various conditions involving OS and inflammation.[79]

8.1.2. α-Tocopherol [vit.E]

Vitamin E (a-tocopherol) is a vital nutrient for humans and animals, acting as a crucial lipid -soluble antioxidant, that neutralizes lipid peroxyl radicals in a lipid environment.Vitamin E also has novel function,including the regulation of gene activity. Clinical evidence for vitamin E in human cholestatic liver disease is more limited, though it has shown benefit in non-alcoholic steatohepatitis (NASH), a condition sharing many oxidative stress mechanisms with cholestatic injury. [80,81]

8.1.3. Polyphenols

Dietary polyphenols, including silymarin (derived from Silybum marianum), resveratrol, curcumin, and epigallocatechin gallate (EGCG), possess pleiotropic antioxidant, anti-inflammatory, and anti-fibrotic properties relevant to cholestatic liver protection.[82] Silymarin, the most studied hepatoprotective polyphenol, inhibits lipid peroxidation, scavenges hydroxyl and peroxyl radicals, stabilizes hepatocellular membranes, and activates Nrf2-driven antioxidant gene expression.[83] Curcumin attenuates BDL-induced hepatic oxidative stress and fibrosis in rodent models through NF-κB inhibition and Nrf2 activation, while resveratrol exerts hepatoprotection via SIRT1-mediated deacetylation of Nrf2 and FOXO transcription factors.[84]

8.2. Pharmacological Interventions

8.2.1. Ursodeoxycholic Acid :Therapeutic Role in Cholestatic Liver Injury

Ursodeoxycholic acid, a hydrophilic bile acid constituting a minor fraction of the normal human bile acid pool, is the sole FDA-approved pharmacological therapy for the management of primary biliary cholangitis and is widely employed in other liver disorders [85] Its hepatoprotective mechanisms encompass replacement of hydrophobic bile acids in the bile acid pool, inhibition of bile acid-induced apoptosis, stimulation of hepatocellular and ductular secretion through post-translational regulation of transporters, and anti-inflammatory effects.[86] Importantly, UDCA attenuates cholestasis-associated oxidative stress by reducing bile acid-induced mitochondrial ROS generation and preserving hepatic GSH contents. [87]

8.2.2. Nor-Ursodeoxycholic Acid and FXR Agonists

Nor-ursodeoxycholic acid (norUDCA), a side-chain-shortened homolog of UDCA, has demonstrated superior anti-cholestatic and anti-fibrotic activity in preclinical PSC models through a cholehepatic shunting mechanism that promotes bicarbonate bile secretion.[88] Obeticholic acid (OCA), a potent synthetic FXR agonist, reduces bile acid synthesis and hepatotoxicity, and is approved for PBC patients with inadequate UDCA response [89]. FXR activation by OCA also upregulates antioxidant gene expression through Nrf2-dependent mechanisms, providing dual anti-cholestatic and antioxidant benefit.[90]

8.2.3. Anti-Inflammatory Agents

Given the central role of inflammatory amplification in oxidative liver injury, anti-inflammatory strategies represent an important adjunctive therapeutic avenue. Selective inhibitors of TNF-α, IL-1β, and the NOX2-mediated oxidative burst have shown hepatoprotective effects in preclinical cholestasis models. The dual 5-lipoxygenase/COX inhibitor BW755C and selective COX-2 inhibitors reduce lipid peroxidation and hepatic injury in BDL rats, albeit with risk of adverse renal effects in the setting of hepatorenal syndrome.[91

8.3. Emerging Therapeutic Strategies

8.3.1. Nrf2 Activators

Pharmacological activation of the Nrf2-Keap1 pathway represents one of the most promising emerging therapeutic interventions aimed at suppressing oxidative stress in cholestatic liver disease.[92] Dimethyl fumarate (DMF), an approved multiple sclerosis therapy with Nrf2-activating properties, reduces hepatic oxidative injury and inflammation in BDL and metabolic liver disease models.[93]

CDDO-methyl ester (bardoxolone methyl) and other synthetic triterpenoid Nrf2 activators demonstrate potent hepatoprotective effects in preclinical studies, though systemic toxicity concerns have tempered clinical enthusiasm for some compounds.[94] Sulforaphane, a naturally occurring isothiocyanate from cruciferous vegetables, activates Nrf2 by modifying Keap1 cysteine residues and has demonstrated hepatoprotective efficacy in rodent cholestasis models with a favorable safety profile.[95]

8.3.2. Gene Therapy

Gene therapy aimed at the liver has emerged as a promising approach,with favorable outcomes in clinical trials for genetic disorders and the potential to open up new therapeutic avenues for cholestatic diseases.[96] Approaches for liver gene therapy have employed both viral and non-viral vectors, including adeno-associated virus, adenovirus and lipid nanoparticles.To explore disease mechanisms, researchers utilized animal model such as bile duct ligation[BDL]and drug-induced cholestasis. Preclinical studies involved hydrodynamic gene delivery, reducing mitochondrial oxidative stress, and anti-fibrotic treatments using various vector types.[97]

8.3.3. Steam Cell Therapy

Inhibiting inflammation, inhibiting apoptosis of liver cells, secreting various soluble factors, and inhibiting oxidative stress.[98] The characteristics of liver injury are rapid onset, rapid disease progression, and its development into acute liver failure. The present treatment is orthotopic liver transplantation. Studies have revealed that MSC transplantation can effectively improve the condition of acute liver injury in rat.[99,100]

8.3.4. Nanotechnology-Based Therapeutic Delivery

The emergence of nanoparticle (NP) technologies has brought forward promising therapeutic approaches for treating liver diseases. Given the liver’s crucial role in detoxification and its natural tendency to interact with circulating nanoparticles it stand out as an optimal target for nanoparticles-based therapies.The damage to hepatocytes is another important cause of liver f ibrosis. Targeting hepatocytes and inhibiting their apoptosis is another important therapeutic strategy for liver fibrosis. NP-based drug delivery systems typically transport hepatoprotective drugs to hepatocytes to preserve liver functionality.[101,102]

9. Nascent Outlook and Changing Landscape

9.1. The Gut-Liver Axis in Cholestatic Oxidative Injury

The gut-liver axis describes to the two way relationship between the gut,including its microbiota, and the liver which result from interactions among signals produced by dietary, genetic and environmental factors.[103] The composition of the intestinal microbiota affects all aspects of gut–liver interactions,ranging from the intestinal epithelium and the gut vascular barrier, to the liver sinusoids,then back to the gut via the biliary tree and the systemic circulation. In a healthy state, the gut microbiota remain within the gut lumen,yet its metabolites act both locally and systemically to maintain homeostasis of the gut–liver axis.[104] A loss of homeostasis at any of these interfaces can result in liver disease. The gut–liver axis permits the tailoring of the interventions to individual patients within a disease population.[105] A relatively underexplored area concern more individualized microbiome risk factors for liver disease. Impaired bile formation or flow can cause cholestatis.The use of prebiotics, diatary substance or postbiotic [inactivated cell] is considered.The prebiotic lactulose, a nonabsorbable disaccharide is use to treat ensephalopathy. Preclinical studies indicate that supplementing with prebiotics like insulin and fructooligosaccharides could lessen liver damage.[106]

9.2. Novel Drug Targets

Ursodeoxycholic acid (UDCA) and other selective FXR agonists have emerged as first-line treatments for cholestatic disease As hydrophilic bile acid, UDCA reduces the pool of toxic hydrophobic bile acid pool in hepatocytes and lessens the detergent action of bile in the bile canaliculi.[107] Patients with Intrahepatic Cholestasis of Pregnancy (ICP), Primary Biliary Cholangitis (PBC), and PFIC3 hve shown clinical improvement with UDCA. Especially during the initial phases of the disease.[108]The NOX family of NADPH oxidases, particularly hepatic NOX2 and NOX4, are being actively investigated as therapeutic targets, with several small-molecule NOX inhibitors demonstrating hepatoprotective efficacy in preclinical studies.Gasotransmitters endogenously produced signaling gases including hydrogen sulfide (H₂S) and carbon monoxide (CO) have attracted growing interest due to their antioxidant, anti-inflammatory, and cytoprotective effects in the liver. Slow-releasing H₂S donors and CO-releasing molecules (CORMs) attenuate oxidative limitation of liver injury and fibrosis in BDL models through targeted inhibition of NOX-mediated superoxide generation, activation of HO-1,along with the regulation of NF-kB and Nrf2 pathways.[109]

9.3. Personalized Medicine Approaches

The recognition of substantial inter-individual heterogeneity in oxidative stress responses to cholestatic liver injury has sparked interest in personalized medicine strategies.[110] Genetic polymorphisms in antioxidant enzyme gene influence susceptibility to oxidative liver injury and may predict therapeutic responses to antioxidant interventions Single nucleotide polymorphisms (SNPs) in bile acid transporter genes (ABCB11, ABCB4, SLC10A1) modulate individual cholestatic susceptibility and severity. Multi-omics approaches integrating genomic, transcriptomic, proteomic, and metabolomic data are increasingly being applied to characterize individual oxidative stress profiles in cholestatic patients, with the goal of identifying predictive biomarker panels for disease progression and treatment response.[111]

9.4. Epigenetic Regulation of Oxidative Stress Responses

Epigenetic regulation has been increasingly been recognized as a fundamental biological process enabling cells to adapt to various types of stress.Oxidative stress, metabolic stress, and inflammatory stress.These change can lead to either widespread or site-specific hypomethylation or hypermethylation of genes involved in stress responses. Oxidative stress serves as a key mechanism driving organelle dysfunction and lipotoxicity in MASLD. In this scenario, the generation of reactive oxygen species (ROS) surpasses the liver’s antioxidant defences, resulting in cellular damage, activation of proinflammatory signaling pathways, and advancing liver damage. Epigenetic regulation is crucial for maintaining metabolic balance and coordinating cellular responses to metabolic stress. Additionally, circadian rhythms and the molecular clock both vital regulators of liver metabolism, are tightly controlled by epigenetic processes. Disturbances in these mechanisms have been linked to metabolic issues, accelerated epigenetic aging, and a higher suscetibility to liver conditions. They hold Considerable potential as biomarkers for disease detection, prognosis, and patient classification. Notably, epigenetic changes are potentially reversible, making them attractive targets for therapeutic approaches. Therefore epigenetic profiling could provide a vital framework for advancing personalized medicine approaches in MASLD and other metabolic diseases. Oxidative stress is a central mechanism underlying organelle dysfunction and lipotoxicity in MASLD. In this context, production of reactive oxygen species (ROS) exceeds the antioxidant capacity of the liver, thereby driving cellular dysfunction, activation of proinflammatory signaling cascades, and progressive liver injury. Growing evidence suggests that OxS induces epigenetic changes using both direct and indirect pathways, as evidenced in research on OxS-related aging and epigenetic modulation.[112]

10. Conclusions

Liver injury in intraabdominal organ in liver and obstruction is various clinical condition involving the common bile duct that lead to cholestatic liver injury.cholestatis when pathogenesis on cholelithiasis biliary and periampallary tumour when they obstruction tend to produce severe cholestatis.FXR agonist obeticholic acid can improved symtoms and liver function.an oxidative stress emerged critical factor linking bile acid toxicity contributes to imflammation, apoptosis, bile acid buildup and mitochondrial dysfuction produce reactive oxygen species, which cause lipid peroxidation. Kupffer cells are liver-resident macrophages and their phagocytic capability allows them to clear pathogens, virus, bacteria, apoptotic cells and cellular debris. On inflammatory and oxidative stress response in NF-kB pathway behavior in hepatic stellate cell. the clinical tragetory on hepatocellular injury they characterized to excessive Ecm.and ALT, ALP, GGT they also serve as marker of protein an oxidative damage in hepatic disease. gene therapy offers a promising strategy to tackle these issues, and various preclinical investigations employing liver-targeted gene therapy in suitable model of both inherited and induced cholestasis have revealed promising effects.