Diagnostic performance of increased prolidase activity in schizophrenia

Assessing the relationship between antipsychotic drug use and prolidase enzyme activity and oxidative stress in schizophrenia patients: a case-control study

BACKGROUND

The relationship between proline, its association with oxidative stress, and its connection to schizophrenia is a subject that has not been sufficiently investigated.

OBJECTIVE

The aim of this study is to evaluate the possible effects of atypical and combined (typical and atypical) antipsychotic use on serum prolidase enzyme activity (SPEA) and serum oxidative stress parameters, and to assess the relationship between SPEA and oxidative stress in patients with schizophrenia.

METHODS

A total of 57 patients with schizophrenia, of which 34 were using atypical (AAPG) and 23 were using combined (typical and atypical) (CAPG) antipsychotic therapy, and 28 healthy volunteers (control group) were included in this case-control study.

RESULTS

SPEA levels of AAPG and CAPG were significantly lower than that of control group ( P  = 0.003). The oxidative stress index (OSI) value of AAPG was significantly higher than the other two groups ( P  = 0.001). SPEA (<1860 U/l) and OSI (≥0.54) could discriminate schizophrenia patients with antipsychotic therapy from control groups ( P  = 0.001 and P  = 0.007, respectively). Lower SPEA levels were associated with antipsychotic use ( P  = 0.007).

CONCLUSION

The SPEA values of patients with schizophrenia on antipsychotics were significantly lower compared to controls. OSI values were significantly higher in atypical antipsychotic recipients compared to those on combined antipsychotics and healthy controls.

Peripheral Complement Factor-Based Biomarkers for Patients with First-Episode Schizophrenia

Objective

Schizophrenia (SCZ) is a severe, protracted neurological disorder that causes disruptive conduct in millions of individuals globally. Discovery of potential biomarkers in clinical settings would lead to the development of efficient diagnostic techniques and an awareness of the disease's pathogenesis and prognosis. The aim of the present study was to discover and identify serum complement factor-based biomarkers in discriminating patients with first-episode SCZ from healthy controls.

Methods

Eighty-nine patients with first-episode SCZ and 89 healthy controls were included in this study. Psychiatric symptom severity of patients with SCZ was measured with the Brief Psychiatric Rating Scale-18 Item Version (BPRS) and the Scales for the Assessment of Negative/Positive Symptoms (SANS/SAPS). A total of 5 complement factors including complement component 1 (C1), C2, C3, C4, and 50% hemolytic complement (CH50) were measured using commercially available enzyme-linked immunosorbent assay (ELISA) kits. The levels of serum complement factors in the SCZ and control groups were compared, and the receiver operating characteristic (ROC) curve method was used to assess the diagnostic values of various complement factors for separating SCZ patients from healthy controls. Pearson's correlation test was used to assess the relationships between serum complement factor concentrations and the psychiatric symptom severity.

Results

There was an increase in serum levels of C1, C2, C3, C4, and CH50 among patients with SCZ. Moreover, based on ROC curve analysis, the AUC value of a combined panel of C1, C2, C3, C4, and CH50 was 0.857 when used to discriminate patients with SCZ from healthy controls. Furthermore, serum C2, C3, and CH50 levels were positively correlated to the scores of SANS, SAPS, and BPRS in patients with SCZ, respectively.

Conclusion

These results suggested that circulating complement factors including C1, C2, C3, C4, and CH50 may have potential in discovering biomarkers for diagnosing first-episode SCZ.

Nano-hesperetin attenuates ketamine-induced schizophrenia-like symptoms in mice: participation of antioxidant parameters

RATIONALE

Antioxidant natural herb hesperetin (Hst) offers powerful medicinal properties. Despite having noticeable antioxidant properties, it has limited absorption, which is a major pharmacological obstacle.

OBJECTIVES

The goal of the current investigation was to determine if Hst and nano-Hst might protect mice against oxidative stress and schizophrenia (SCZ)-like behaviors brought on by ketamine (KET).

METHODS

Seven treatment groups (n=7) were created for the animals. For 10 days, they received distilled water or KET (10 mg/kg) intraperitoneally (i.p). From the 11th to the 40th day, they received daily oral administration of Hst and nano-Hst (10, 20 mg/kg) or vehicle. With the use of the forced swimming test (FST), open field test (OFT), and novel object recognition test (NORT), SCZ-like behaviors were evaluated. Malondialdehyde (MDA) and glutathione levels and antioxidant enzyme activities were assessed in the cerebral cortex.

RESULTS

Our findings displayed that behavioral disorders induced by KET would be improved by nano-Hst treated. MDA levels were much lower after treatment with nano-Hst, and brain antioxidant levels and activities were noticeably higher. The mice treated with nano-Hst had improved outcomes in the behavioral and biochemical tests when compared to the Hst group.

CONCLUSIONS

Our study's findings showed that nano-Hst had a stronger neuroprotective impact than Hst. In cerebral cortex tissues, nano-Hst treatment dramatically reduced KET-induced (SCZ)-like behavior and oxidative stress indicators. As a result, nano-Hst may have more therapeutic potential and may be effective in treating behavioral impairments and oxidative damage brought on by KET.

Serum NOX1 and Raftlin as New Potential Biomarkers of Interest in Schizophrenia: A Preliminary Study

Introduction

There is increasing evidence that oxidative stress (OS) and neuroinflammation play a role in the neuroprogression of schizophrenia (SCZ). Promising novel candidates which have been proposed in the search for biomarkers of psychotic illness include NADPH oxidase 1,2 (NOX1,2) and raftlin. NOX1 from the NOX family is the main source of physiological reactive oxygen species (ROS) and raftlin, the main lipid raft protein, is associated with inflammatory processes. The aim of the present study was to evaluate serum NOX1 and raftlin levels in chronic stable patients with SCZ.

Methods

We measured serum NOX1 and raftlin levels from 45 clinically stable patients with SCZ and 45 healthy controls (HCs) matched for age, sex, and body-mass index. The Positive and Negative Syndrome Scale was applied to the patient group to evaluate the severity of psychotic symptoms.

Results

NOX1 and raftlin levels in the patients were statistically significantly higher than the HCs (NOX1 p<0.001, raftlin p<0.001). Both parameters showed very good diagnostic performance (NOX1 AUC = 0.931, raftlin AUC = 0.915). We obtained positive and significant correlations between serum levels of both biomarkers and symptom severity.

Discussion

This preliminary study indicating elevations in serum NOX1 and raftlin levels in patients with SCZ supports the importance of OS and inflammatory processes in the etiopathogenesis of the illness.

Diagnostic Performance of Increased Malondialdehyde Level and Oxidative Stress in Patients with Schizophrenia

Introduction:

Schizophrenia is typically diagnosed through interviews with patients and their relatives. Thus, molecular biomarkers for this mental illness have recently become a hot topic for research. Oxidative stress and antioxidant parameters, such as catalase (CAT), superoxide dismutase (SOD) and malondialdehyde (MDA), have been investigated in schizophrenia; however, no studies have been conducted on the diagnostic performance of oxidative parameters. The goal of the present study is to examine the serum levels of SOD, CAT and MDA and to test the diagnostic performance of MDA in patients with schizophrenia.

Methods:

Thirty patients with schizophrenia and 30 healthy gender– and age-matched controls were included in our study. Symptom severity in the patient group was rated using the Positive and Negative Syndrome Scale (PANSS).

Results:

The serum levels of MDA, SOD and CAT were found to be significantly increased in patients with schizophrenia compared to the control group. A receiver operating characteristic curve showed a cut-off point of 2.72 nmol/ml for the MDA diagnostic measure. No significant correlation was found (p>0.05) between MDA, SOD and CAT activity and PANSS scores or the chlorpromazine equivalent and clinical characteristics.

Conclusion:

In summary, we found higher serum levels of SOD, CAT and MDA in patients with schizophrenia compared to healthy controls. MDA is considered a very good diagnostic lipid peroxidation marker, and further studies should be done to test its validity in patients with schizophrenia.

PROLIDASE: A Review from Discovery to its Role in Health and Disease

Prolidase (peptidase D), encoded by the PEPD gene, is a ubiquitously expressed cytosolic metalloproteinase, the only enzyme capable of cleaving imidodipeptides containing C-terminal proline or hydroxyproline. Prolidase catalyzes the rate-limiting step during collagen recycling and is essential in protein metabolism, collagen turnover, and matrix remodeling. Prolidase, therefore plays a crucial role in several physiological processes such as wound healing, inflammation, angiogenesis, cell proliferation, and carcinogenesis. Accordingly, mutations leading to loss of prolidase catalytic activity result in prolidase deficiency a rare autosomal recessive metabolic disorder characterized by defective wound healing. In addition, alterations in prolidase enzyme activity have been documented in numerous pathological conditions, making prolidase a useful biochemical marker to measure disease severity. Furthermore, recent studies underscore the importance of a non-enzymatic role of prolidase in cell regulation and infectious disease. This review aims to provide comprehensive information on prolidase, from its discovery to its role in health and disease, while addressing the current knowledge gaps.

Plasma prolidase levels are high in schizophrenia but not in first-episode psychosis

An increasing number of studies have focussed on the neurobiology of schizophrenia (SCH), contributing to a better understanding of this disorder. Prolidase is a metalloprotease found in various tissues, which has been associated with the concentrations of proline, a neurotransmitter, in the brain. There is evidence to suggest that elevated proline levels play a role in SCH. The aim of the present study was to compare plasma proline levels in patients with drug-naive first-episode psychosis (FEP) and in those with SCH. Patients diagnosed with FEP (n = 26) and SCH (n = 26) were recruited for this study, in addition to healthy control volunteers (n = 26). Plasma prolidase levels were found to be elevated in the SCH group compared to drug-naive FEP and healthy control groups. This finding indicates that prolidase levels are higher in SCH patients, while levels in patients with drug-naive FEP are similar to those of healthy control. Follow-up studies are needed to provide a better understanding of prolidase in the etiopathogenesis of SCH.

Prolidase - A protein with many faces

Prolidase is a metal-dependent peptidase specialized in the cleavage of dipeptides containing proline or hydroxyproline on their C-termini. Prolidase homologues are found in all kingdoms of life. The importance of prolidase in human health is underlined by a rare hereditary syndrome referred to as Prolidase Deficiency. A growing number of studies highlight the importance of prolidase in various other human conditions, including cancer. Some recent studies link prolidase's activity-independent regulatory role to tumorigenesis. Furthermore, the enzyme or engineered variants have some applications in biotechnology. In this short review, we aim to highlight different aspects of the protein the importance of which is increasingly recognized over the last years.

Increased prolidase activity in Alzheimer's dementia: A case-control study

Prolidase enzyme, which catalyzes the final step in collagen metabolism can influence the cognitive functions through changes in extracellular matrix (ECM) resulting in altered synaptic connectivity in Alzheimer's disease (AD). In this study, it was found that the prolidase activity was significantly higher (p = 0.0016) in AD subjects (5.62 ± 2.05 U/ mL) than control group (4.45 ± 0.92 U/ mL). The increase was significant beginning at mild AD (p = 0.006) with an inverse correlation with HMSE scores (p = 0.0344), thus implying that prolidase mediated alterations in ECM may be associated with the cognitive deficits seen in AD.

Current Understanding of the Emerging Role of Prolidase in Cellular Metabolism

Prolidase [EC 3.4.13.9], known as PEPD, cleaves di- and tripeptides containing carboxyl-terminal proline or hydroxyproline. For decades, prolidase has been thoroughly investigated, and several mechanisms regulating its activity are known, including the activation of the β₁-integrin receptor, insulin-like growth factor 1 receptor (IGF-1) receptor, and transforming growth factor (TGF)-β₁ receptor. This process may result in increased availability of proline in the mitochondrial proline cycle, thus making proline serve as a substrate for the resynthesis of collagen, an intracellular signaling molecule. However, as a ligand, PEPD can bind directly to the epidermal growth factor receptor (EGFR, epidermal growth factor receptor 2 (HER2)) and regulate cellular metabolism. Recent reports have indicated that PEPD protects p53 from uncontrolled p53 subcellular activation and its translocation between cellular compartments. PEPD also participates in the maturation of the interferon α/β receptor by regulating its expression. In addition to the biological effects, prolidase demonstrates clinical significance reflected in the disease known as prolidase deficiency. It is also known that prolidase activity is affected in collagen metabolism disorders, metabolic, and oncological conditions. In this article, we review the latest knowledge about prolidase and highlight its biological function, and thus provide an in-depth understanding of prolidase as a dipeptidase and protein regulating the function of key biomolecules in cellular metabolism.

ALDH4A1 expression levels are elevated in postmortem brains of patients with schizophrenia and are associated with genetic variants in enzymes related to proline metabolism

BACKGROUND

The molecular mechanisms underlying schizophrenia remain largely unclear, and we recently identified multiple proteins significantly altered in the postmortem prefrontal cortex (PFC) of schizophrenia patients amongst which aldehyde dehydrogenase 4 family member A1 (ALDH4A1) was especially elevated. In this study, we aimed to investigate the expression of ALDH4A1 in the PFC and superior temporal gyrus (STG) and to elucidate functional correlations between schizophrenia risk alleles and molecular expression profiles in the postmortem brains of patients with schizophrenia.

METHODS

The levels of ALDH4A1 protein expression in the PFC and STG in postmortem brains from 24 patients with schizophrenia, 8 patients with bipolar disorder, and 32 controls were assessed using enzyme-linked immunosorbent assay. Moreover, we explored the associations between ALDH4A1 expression and genetic variants in enzymes associated with proline metabolism, including ALDH4A1 (schizophrenia [n = 22], bipolar disorder [n = 6], controls [n = 11]).

RESULTS

ALDH4A1 levels were significantly elevated in both the PFC and STG in patients with schizophrenia and tended to elevate in patients with bipolar disorder. Furthermore, ALDH4A1 expression levels in the PFC were significantly associated with the following three single-nucleotide polymorphisms: rs10882639, rs33823, rs153508. We also found partial coexpression of ALDH4A1 in mitochondria in a subset of putative astrocytes of postmortem brain.

LIMITATIONS

Our study population was relatively small, particularly for a genetic study.

CONCLUSION

These findings indicate that altered expression of ALDH4A1 may reflect the potential molecular mechanisms underlying the pathogenesis of schizophrenia and bipolar disorder, and may aid in the development of novel drug therapies.

A Novel Role of Prolidase in Cocaine-Mediated Breach in the Barrier of Brain Microvascular Endothelial Cells

Cocaine use is associated with breach in the blood brain barrier (BBB) and increased HIV-1 neuro-invasion. We show that the cellular enzyme "Prolidase" plays a key role in cocaine-induced disruption of the BBB. We established a barrier model to mimic the BBB by culturing human brain microvascular endothelial cells (HBMECs) in transwell inserts. In this model, cocaine treatment enhanced permeability of FITC-dextran suggesting a breach in the barrier. Interestingly, cocaine treatment increased the activity of matrix metallo-proteinases that initiate degradation of the BBB-associated collagen. Cocaine exposure also induced prolidase expression and activity in HBMECs. Prolidase catalyzes the final and rate-limiting step of collagen degradation during BBB remodeling. Knock-down of prolidase abrogated cocaine-mediated increased permeability suggesting a direct role of prolidase in BBB breach. To decipher the mechanism by which cocaine regulates prolidase, we probed the inducible nitric oxide synthase (iNOS) mediated phosphorylation of prolidase since mRNA levels of the protein were not altered upon cocaine treatment. We observed increased iNOS expression concurrent with increased prolidase phosphorylation in cocaine treated cells. Subsequently, inhibition of iNOS decreased prolidase phosphorylation and reduced cocaine-mediated permeability. Finally, cocaine treatment increased transmigration of monocytic cells through the HBMEC barrier. Knock-down of prolidase reduced cocaine-mediated monocyte transmigration, establishing a key role of prolidase in cocaine-induced breach in endothelial cell barrier.

Increased prolidase activity and high blood monocyte counts in pediatric bipolar disorder

Various psychological, genetic, and biochemical factors are thought to be involved in the aetiology of pediatric bipolar disorder (PBD). However, few studies have evaluated the biochemical basis of PBD. The level of peripheral blood mononuclear cells and serum prolidase activity were determined in PBD and matched healthy comparison subjects. Blood from 38 (age range: 14-17) PBD-type I and 37 age- and gender-matched healthy comparison subjects was analyzed for numbers of neutrophils, lymphocytes, monocytes, lymphocyte-to-monocyte ratio (LMR), neutrophil-to-lymphocyte ratio (NLR) and serum prolidase activity. The prolidase activity and monocyte count were significantly higher in PBD than the control group. There were no significant differences in numbers of neutrophils, lymphocytes, LMR and NLR between the patient and control groups. These results suggest that the immune system and prolidase activity may be activated in PBD. There is a clinical benefit from the early detection of PBD using serum prolidase activity levels and monocyte counts. Especially, prolidase activity may be a trait marker for diagnosing PBD. However, further studies are needed to verify these findings.

Plasma prolidase levels as a biomarker for polycystic ovary syndrome

Aim: Assessment of plasma prolidase levels in polycystic ovary syndrome (PCOS). Patients & methods: PCOS patients were screened according to Rotterdam Criterion and prolidase levels were measured. Results: A total of 170 patients and 160 controls were recruited for the study and it was found that prolidase levels were significantly higher in PCOS group (991.10 ± 39.52) than control (621.89 ± 23.94). Furthermore it has been found that prolidase levels increase with the number of cysts in ovaries. Conclusion: Significant difference between prolidase levels in PCOS and control shows that it may be used as a diagnostic marker for disease. In addition to this, there is a positive correlation found between prolidase levels and number of cysts, hence may be used as a prognostic marker to monitor disease status.

Elevated serum levels of malondialdehyde and cortisol are associated with major depressive disorder: A case-control study

Objectives:

Major depressive disorder is diagnosed on the basis of patient’s self-reported experiences, behavior reported by relatives, and a mental status examination, and yet we do not have any reliable biomarker for this. Mood-regulating pathways are affected by oxidative injury to lipids and cortisol is released into the blood due to stimulation of corticotrophin receptors in the adrenal cortex. Here, we aimed to determine serum levels of malondialdehyde and cortisol in major depressive disorder patients and controls.

Methods:

We collected blood samples from 247 major depressive disorder patients and 248 controls. Serum levels of malondialdehyde and cortisol were measured by ultraviolet spectrophotometry and enzyme-linked immunosorbent assay kit, respectively.

Results:

We found malondialdehyde levels were significantly higher in patients than controls, with mean ± standard deviation at 4.49 ± 1.37 and 2.87 ± 0.82 µmol/L, respectively, p < 0.001. Cortisol levels were also found significantly higher in patients than controls, with mean ± SD at 19.22 ± 1.64 and 17.37 ± 1.34 µg/dL, respectively, p < 0.001. Significant negative correlation was observed between serum levels of malondialdehyde and cortisol in patients (r =−0.170, p = 0.021). Receiver operating characteristic analysis showed good diagnostic value for malondialdehyde and cortisol, with the area under the curve at 0.853 and 0.819, respectively.

Conclusion:

The present study suggests that increased serum levels of malondialdehyde and cortisol are strongly associated with major depressive disorder. We believe elevations of malondialdehyde and cortisol in serum level arise independently and they could serve as biomarkers for major depressive disorder.

The Diagnostic Value of Malondialdehyde, Superoxide Dismutase and Catalase Activity in Drug Naïve, First Episode, Non-Smoker Generalized Anxiety Disorder Patients

Objective

Generalized anxiety disorder (GAD) is a common anxiety disorder. Although lots of research done to reveal neurobiological basis of GAD, it is still unclear. Diagnosis of GAD depends on subjective complaints of patients, thus the need for a biological marker is constantly emerging. In this study, we aimed to investigate diagnostic value of malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) in GAD.

Methods

We evaluated MDA, SOD, and CAT levels in peripheral blood of 46 patients and 45 controls. MDA was measured with Ohkawa’s methods, SOD was measured with Fridovich method, and CAT was measured with Beutler’s method.

Results

MDA was significantly increased in patients than controls, medians 4.05 nmol/mg and 1.71 nmol/mg respectively, p<0.001; SOD and CAT activity was significantly decreased in patients than controls, medians of SOD were 159.07 U/mg and 301.87 U/mg, p<0.001 respectively, medians for CAT were 138.47 U/mg and 160.60 U/mg respectively. We found high correlation between Hamilton Anxiety Rating Scale and SOD, MDA r values were 0.723 and 0.715 respectively, p<0.001 for both. Receiver operator characteristic (ROC) curve analysis showed high diagnostic performance for MDA and SOD, low diagnostic performance for CAT, areas under curve were 1.0, 1.0, and 0.648 respectively.

Conclusion

Our results reveal possible diagnostic value of MDA, less likely of SOD but not CAT. Future studies should investigate diagnostic value of oxidants and antioxidantn enzymes in larger samples and include diagnostic value of these parameters.

Evaluation of Paraoxonase, Arylesterase and Malondialdehyde Levels in Schizophrenia Patients Taking Typical, Atypical and Combined Antipsychotic Treatment

Objective

Human serum paraoxonase (PON1) prevents lipids from peroxidation and functions as an antioxidant mechanism. Malonyldialdehyde (MDA) is the final product of lipid peroxidation and can be used as an indicator of oxidative stress. The aim of this study was to investigate PON1, MDA, and arylesterase (ARY) levels in schizophrenic patients who are taking typical, atypical, or combined (typical and atypical) antipsychotic drug treatment, with respect to those of healthy controls.

Methods

We evaluated 41 patients (11 taking typical antipsychotics, 19 taking atypical antipsychotics, 11 taking combined anti-psychotics) and 43 healthy controls.

Results

MDA levels were higher in schizophrenic patients taking typical antipsychotics compared with healthy controls (p=0.001). ARY levels were higher in patients taking atypical antipsychotics compared with healthy controls (p=0.005). PON1 activity was similar in all groups.

Conclusion

Our results indicate that treatment with typical antipsychotic drugs could be related to increased MDA levels; and antipsychotic medication may increase PON1 levels in schizophrenic patients.

Serum levels of G protein-coupled estrogen receptor 1 (GPER1) in drug-naive patients with generalized anxiety disorder

Sex hormones, particularly estrogen, are suggested to play a role in the physiopathology of generalized anxiety disorder (GAD). Estrogen functions through the estrogen receptors alpha and beta and the recently discovered G protein-coupled estrogen receptor 1 (GPER1). This study aimed, for the first time, to evaluate serum GPER1 levels in drug-naive patients with GAD. This study included 40 newly diagnosed drug-naive patients with GAD aged between 18 and 50 years and 40 age- and gender-matched healthy controls. Medical histories were obtained, and physical examinations and laboratory tests were conducted; the Hamilton Anxiety Rating Scale (HAM-A) was also used for all participants. Serum GPER1 levels were measured. The serum GPER1 level was significantly higher in the patients with GAD than in the controls. A positive significant correlation was observed between the GPER1 level and the HAM-A score. The receiver operating characteristic analysis revealed a sensitivity, specificity, positive predictive value, and negative predictive value of 85.0%, 82.5%, 82.9%, and 84.6%, respectively, for the presence of anxiety when the serum GPER1 value was ≥0.14 (the area under the curve was 0.904.). In conclusion, this study demonstrated that GPER1 levels were associated with the anxiety levels of patients, and that the serum GPER1 level was a valuable predictor of the presence of anxiety independent of gender.