Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

The Endogenous Opioid System in Schizophrenia and Treatment Resistant Schizophrenia: Increased Plasma Endomorphin 2, and κ and μ Opioid Receptors are Associated with Interleukin-6

Version 1 : Received: 13 January 2020 / Approved: 13 January 2020 / Online: 13 January 2020 (04:15:01 CET)

How to cite: Moustafa, S.R.; Al-Rawi, K.F.; Al-Dujaili, A.H.; Supasitthumrong, T.; Al-Hakeim, H.K.; Maes, M. The Endogenous Opioid System in Schizophrenia and Treatment Resistant Schizophrenia: Increased Plasma Endomorphin 2, and κ and μ Opioid Receptors are Associated with Interleukin-6. Preprints 2020, 2020010138 (doi: 10.20944/preprints202001.0138.v1). Moustafa, S.R.; Al-Rawi, K.F.; Al-Dujaili, A.H.; Supasitthumrong, T.; Al-Hakeim, H.K.; Maes, M. The Endogenous Opioid System in Schizophrenia and Treatment Resistant Schizophrenia: Increased Plasma Endomorphin 2, and κ and μ Opioid Receptors are Associated with Interleukin-6. Preprints 2020, 2020010138 (doi: 10.20944/preprints202001.0138.v1).

Abstract

Background: Activation of the immune-inflammatory response system (IRS) and the compensatory immune-regulatory system (CIRS) play a key role in SCZ and treatment resistant SCZ. There are only few data on immune and endogenous opioid system (EOS) interactions in SCZ and treatment resistant SCZ.Aim of the study: We examined serum β-endorphin, endomorphin-2 (EM2), mu-opioid (MOR) and kappa-opioid (KOR) receptors, and interleukin (IL)-6 and IL-10 in 60 non responders to treatment (NRTT), 55 partial RTT (PRTT) and 43 normal controls.Results: Serum EM2, KOR, MOR, IL-6 and IL-10 were significantly increased in SCZ as compared with controls. β-endorphin, EM2, MOR and IL-6 were significantly higher in NRTT than in PRTT. There were significant correlations between IL-6, on the one hand, and β-endorphin, EM2, KOR, and MOR, on the other, while IL-10 was significantly correlated with MOR only. A large part of the variance in negative symptoms, psychosis, hostility, excitation, mannerism, psychomotor retardation and formal thought disorders was explained by the combined effects of EM2 and MOR with or without IL-6 while increased KOR was significantly associated with all symptom dimensions. Increased MOR, KOR, EM2 and IL-6 were also associated with neurocognitive impairments including in episodic, semantic and working memory and executive functions.Conclusion: The EOS contributes to SCZ symptomatology, neurocognitive impairments and a non-response to treatment. In SCZ, EOS peptides/receptors may exert CIRS functions, whereas increased KOR levels may contribute to the pathophysiology of SCZ and EM2 and KOR to a non-response to treatment.

Subject Areas

inflammation; Schizophrenia; treatment resistance; neurocognition; neuroimmunomodulation

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