Angiotensin converting enzyme activity is positively associated with IL-17a levels in patients with schizophrenia

Comparative estimation of the effects of antihypertensive medications on schizophrenia occurrence: a multinational observational cohort study

BACKGROUND

The association between antihypertensive medication and schizophrenia has received increasing attention; however, evidence of the impact of antihypertensive medication on subsequent schizophrenia based on large-scale observational studies is limited. We aimed to compare the schizophrenia risk in large claims-based US and Korea cohort of patients with hypertension using angiotensin-converting enzyme (ACE) inhibitors versus those using angiotensin receptor blockers (ARBs) or thiazide diuretics.

METHODS

Adults aged 18 years who were newly diagnosed with hypertension and received ACE inhibitors, ARBs, or thiazide diuretics as first-line antihypertensive medications were included. The study population was sub-grouped based on age (> 45 years). The comparison groups were matched using a large-scale propensity score (PS)-matching algorithm. The primary endpoint was incidence of schizophrenia.

RESULTS

5,907,522; 2,923,423; and 1,971,549 patients used ACE inhibitors, ARBs, and thiazide diuretics, respectively. After PS matching, the risk of schizophrenia was not significantly different among the groups (ACE inhibitor vs. ARB: summary hazard ratio [HR] 1.15 [95% confidence interval, CI, 0.99-1.33]; ACE inhibitor vs. thiazide diuretics: summary HR 0.91 [95% CI, 0.78-1.07]). In the older subgroup, there was no significant difference between ACE inhibitors and thiazide diuretics (summary HR, 0.91 [95% CI, 0.71-1.16]). The risk for schizophrenia was significantly higher in the ACE inhibitor group than in the ARB group (summary HR, 1.23 [95% CI, 1.05-1.43]).

CONCLUSIONS

The risk of schizophrenia was not significantly different between the ACE inhibitor vs. ARB and ACE inhibitor vs. thiazide diuretic groups. Further investigations are needed to determine the risk of schizophrenia associated with antihypertensive drugs, especially in people aged > 45 years.

Targeting the Renin-Angiotensin System (RAS) for Neuropsychiatric Disorders

BACKGROUND

Neuropsychiatric disorders, such as mood disorders, schizophrenia, and Alzheimer's disease (AD) and related dementias, are associated to significant morbidity and mortality worldwide. The pathophysiological mechanisms of neuropsychiatric disorders remain to be fully elucidated, which has hampered the development of effective therapies. The Renin Angiotensin System (RAS) is classically viewed as a key regulator of cardiovascular and renal homeostasis. The discovery that RAS components are expressed in the brain pointed out a potential role for this system in central nervous system (CNS) pathologies. The understanding of RAS involvement in the pathogenesis of neuropsychiatric disorders may contribute to identifying novel therapeutic targets.

AIMS

We aim to report current experimental and clinical evidence on the role of RAS in physiology and pathophysiology of mood disorders, schizophrenia, AD and related dementias. We also aim to discuss bottlenecks and future perspectives that can foster the development of new related therapeutic strategies.

CONCLUSION

The available evidence supports positive therapeutic effects for neuropsychiatric disorders with the inhibition/antagonism of the ACE/Ang II/AT1 receptor axis or the activation of the ACE2/Ang-(1-7)/Mas receptor axis. Most of this evidence comes from pre-clinical studies and clinical studies lag much behind, hampering a potential translation into clinical practice.

Diminished treatment response in relapsed versus first-episode schizophrenia as revealed by a panel of blood-based biomarkers: A combined cross-sectional and longitudinal study

There is a paucity of biomarkers for the prediction of treatment response in schizophrenia. In this study, we aimed to investigate whether diminished antipsychotic treatment response in relapsed versus first-episode schizophrenia can be revealed and predicted by a panel of blood-based biomarkers. A cross-sectional cohort consisting of 655 schizophrenia patients at different episodes and 606 healthy controls, and a longitudinal cohort including 52 first-episode antipsychotic-naïve schizophrenia patients treated with the same antipsychotic drugs during the 5-year follow-up of their first three episodes were enrolled. Plasma biomarker changes and symptom improvement were compared between the drug-free phase of psychosis onset and after 4 weeks of atypical antipsychotic drug (AAPD) treatment. In response to treatment, the extent of changes in the biomarkers of bioenergetic, purinergic, phospholipid and neurosteroid metabolisms dwindled down as number of episode and illness duration increased in relapsed schizophrenia. The changes of creatine, inosine, progesterone, allopregnanolone, cortisol and PE(16:0/22:6) were significantly correlated with the improvement of symptomatology. Inosine and progesterone at baseline were shown to be strong predictive biomarkers of treatment response. The results suggest that AAPD treatment response is diminished in the context of relapse, and our findings open new avenues for understanding the pathophysiology of treatment-resistance schizophrenia.

Role of interleukin 8 in depression and other psychiatric disorders

Low grade neuroinflammation has been suggested as one of the underlying mechanisms of many psychiatric diseases as well as cognitive disorders. Interleukin 8 (IL-8), a proinflammatory cytokine produced by many cell types including macrophage and microglia, mainly functions as a neutrophil chemoattractant in the bloodstream. IL-8 is also found in the brain, where it is released from microglia in response to proinflammatory stimuli. In this review, we highlight studies focusing on the role of IL-8 in psychiatric diseases such as major depression, bipolar disorder, schizophrenia, sleep disorder, autism spectrum disorder, anxiety disorders and dementia. Increased peripheral IL-8 levels have been reported in these diseases, particularly in schizophrenic disorder, bipolar disorder, obstructive sleep apnea and autism spectrum disorder. The literature on IL-8 and major depression is inconsistent. IL-8 has been found to be a factor associated with schizophrenic prognosis and therapeutic response, and may affect a wide range of symptomatology. Considering that the exact role of immune alterations is still under research, the success of immune-based therapies in psychiatric diseases is limited for the time being.

How Does SARS-CoV-2 Affect the Central Nervous System? A Working Hypothesis

Interstitial pneumonia was the first manifestation to be recognized as caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); however, in just a few weeks, it became clear that the coronavirus disease-2019 (COVID-19) overrun tissues and more body organs than just the lungs, so much so that it could be considered a systemic pathology. Several studies reported the involvement of the conjunctiva, the gut, the heart and its pace, and vascular injuries such as thromboembolic complications and Kawasaki disease in children and toddlers were also described. More recently, it was reported that in a sample of 214 SARS-CoV-2 positive patients, 36.4% complained of neurological symptoms ranging from non-specific manifestations (dizziness, headache, and seizures), to more specific symptoms such hyposmia or hypogeusia, and stroke. Older individuals, especially males with comorbidities, appear to be at the highest risk of developing such severe complications related to the Central Nervous System (CNS) involvement. Neuropsychiatric manifestations in COVID-19 appear to develop in patients with and without pre-existing neurological disorders. Growing evidence suggests that SARS-CoV-2 binds to the human Angiotensin-Converting Enzyme 2 (ACE2) for the attachment and entrance inside host cells. By describing ACE2 and the whole Renin Angiotensin Aldosterone System (RAAS) we may better understand whether specific cell types may be affected by SARS-CoV-2 and whether their functioning can be disrupted in case of an infection. Since clear evidences of neurological interest have already been shown, by clarifying the topographical distribution and density of ACE2, we will be able to speculate how SARS-CoV-2 may affect the CNS and what is the pathogenetic mechanism by which it contributes to the specific clinical manifestations of the disease. Based on such evidences, we finally hypothesize the process of SARS-CoV-2 invasion of the CNS and provide a possible explanation for the onset or the exacerbation of some common neuropsychiatric disorders in the elderly including cognitive impairment and Alzheimer disease.

Evaluation of NDEL1 oligopeptidase activity in blood and brain in an animal model of schizophrenia: effects of psychostimulants and antipsychotics

Nuclear distribution element-like 1 (NDEL1) enzyme activity is important for neuritogenesis, neuronal migration, and neurodevelopment. We reported previously lower NDEL1 enzyme activity in blood of treated first episode psychosis and chronic schizophrenia (SCZ) compared to healthy control subjects, with even lower activity in treatment resistant chronic SCZ patients, implicating NDEL1 activity in SCZ. Herein, higher NDEL1 activity was observed in the blood and several brain regions of a validated animal model for SCZ at baseline. In addition, long-term treatment with typical or atypical antipsychotics, under conditions in which SCZ-like phenotypes were reported to be reversed in this animal model for SCZ, showed a significant NDEL1 activity reduction in blood and brain regions which is in line with clinical data. Importantly, these results support measuring NDEL1 enzyme activity in the peripheral blood to predict changes in NDEL1 activity in the CNS. Also, acute administration of psychostimulants, at levels reported to induce SCZ-like phenotype in normal rat strains, increased NDEL1 enzyme activity in blood. Therefore, alterations in NDEL1 activity after treatment with antipsychotics or psychostimulants may suggest a possible modulation of NDEL1 activity secondary to neurotransmission homeostasis and provide new insights into the role of NDEL1 in SCZ pathophysiology.

ACE activity in blood and brain axis in an animal model for schizophrenia: Effects of dopaminergic manipulation with antipsychotics and psychostimulants

Objectives: Angiotensin I-converting enzyme (ACE) was initially correlated with schizophrenia (SCZ) in studies showing a correlation of ACE increased enzyme activity with memory impairments. Possible role for ACE in SCZ was also suggested by ACE activity interaction with dopaminergic mechanisms to modulate abnormalities of sensorimotor gating. In addition, we have demonstrated higher ACE activity in blood of SCZ subjects, its implication in cognitive performance in SCZ and its power as a predictor for SCZ diagnosis.Methods: ACE activity was determined in the serum and in selected brain regions of an animal model presenting SCZ-like behaviour, before and after the treatment with typical and atypical antipsychotics, and also in the serum of animals receiving the psychostimulants amphetamine/lisdexamphetamine.Results: Dopaminergic manipulations with antipsychotics and psychostimulants influenced the ACE activity, but with no correlation with the animal blood pressure.Conclusions: The validity of measuring ACE activity in animal blood to predict activity in the CNS, as well as the lack of correlation between the activity and blood pressure, before and after the treatment with antipsychotics, were confirmed here. Correlations of the present findings with data from clinical studies also strengthen the value of this animal model for studying several aspects of SCZ.

The Role of Aberrations in the Immune-Inflammatory Response System (IRS) and the Compensatory Immune-Regulatory Reflex System (CIRS) in Different Phenotypes of Schizophrenia: the IRS-CIRS Theory of Schizophrenia

Several lines of evidence indicate that aberrations in immune-inflammatory pathways may contribute to the pathophysiology of schizophrenia spectrum disorders. Here, we propose a novel theoretical framework that was previously developed for major depression and bipolar disorder, namely, the compensatory immune-regulatory reflex system (CIRS), as applied to the neuro-immune pathophysiology of schizophrenia and its phenotypes, including first-episode psychosis (FEP), acute relapses, chronic and treatment-resistant schizophrenia (TRS), comorbid depression, and deficit schizophrenia. These schizophrenia phenotypes and manifestations are accompanied by increased production of positive acute-phase proteins, including haptoglobin and α2-macroglobulin, complement factors, and macrophagic M1 (IL-1β, IL-6, and TNF-α), T helper (Th)-1 (interferon-γ and IL-2R), Th-2 (IL-4, IL-5), Th-17 (IL-17), and T regulatory (Treg; IL-10 and transforming growth factor (TGF)-β1) cytokines, cytokine-induced activation of the tryptophan catabolite (TRYCAT) pathway, and chemokines, including CCL-11 (eotaxin), CCL-2, CCL-3, and CXCL-8. While the immune profiles in the different schizophrenia phenotypes indicate the activation of the immune-inflammatory response system (IRS), there are simultaneous signs of CIRS activation, including increased levels of the IL-1 receptor antagonist (sIL-1RA), sIL-2R and tumor necrosis factor-α receptors, Th-2 and Treg phenotypes with increased IL-4 and IL-10 production, and increased levels of TRYCATs and haptoglobin, α2-macroglobulin, and other acute-phase reactants, which have immune-regulatory and anti-inflammatory effects. Signs of activated IRS and CIRS pathways are also detected in TRS, chronic, and deficit schizophrenia, indicating that these conditions are accompanied by a new homeostatic setpoint between upregulated IRS and CIRS components. In FEP, increased baseline CIRS activity is a protective factor that may predict favorable clinical outcomes. Moreover, impairments in the CIRS are associated with deficit schizophrenia and greater impairments in semantic and episodic memory. It is concluded that CIRS plays a key role in the pathophysiology of schizophrenia by negatively regulating the primary IRS and contributing to recovery from the acute phase of illness. Therefore, components of the CIRS may offer promising therapeutic targets for schizophrenia.

Lower circulating levels of angiotensin-converting enzyme (ACE) in patients with schizophrenia

This study aimed at evaluating changes in the renin-angiotensin system (RAS) in patients with schizophrenia in comparison with controls. Plasma levels of angiotensin-converting enzyme (ACE), ACE2, angiotensin (Ang)-(1-7) and Ang II were assessed in 25 patients with schizophrenia and 20 controls. Patients with schizophrenia presented decreased levels of ACE compared to controls [median (25th-75th percentiles) = 434.79 (341.15-524.02) vs. 508.49 (396.34-608.72); p < 0.05]. No significant differences were found regarding ACE2, Ang-(1-7) and Ang II levels. There were no associations between the measured molecules and clinical parameters. Our results corroborate the hypothesis that the RAS is involved in the pathophysiology of schizophrenia.

Profiling inflammatory signatures of schizophrenia: A cross-sectional and meta-analysis study

We aimed to profile a broad panel of inflammatory markers in patients with schizophrenia and healthy controls. Additionally, we performed a meta-analysis of chemokine alterations that have not been subjected to quantitative synthesis so far. We recruited 78 patients with schizophrenia and 78 healthy controls, and measured inflammatory markers using the Luminex technology. After adjustment for multiple testing, we found elevated levels of interleukin (IL)-1 receptor antagonist (IL-1RA), IL-6, IL-7, IL-8, IL-9, IL-10, IL-13, interferon-γ, eotaxin-1, granulocyte-macrophage colony-stimulating factor (GM-CSF), monocyte chemoattractant protein-1 (MCP-1), platelet-derived growth factor with two B subunits (PDGF-BB), macrophage inflammatory protein (MIP)-1α, MIP-1β, vascular endothelial growth factor A (VEGF-A) and RANTES in multiple-episode schizophrenia (MES) patients. These differences, except for the difference in eotaxin-1 levels, appeared to be significant after co-varying for the dosage of antipsychotics. There were no significant differences in the levels of immune markers between first-episode schizophrenia (FES) patients and controls. Our meta-analysis revealed elevated levels of MCP-1 in first-episode psychosis (FEP) patients and MES individuals. Other chemokine alterations (elevated levels of IL-8, eotaxin-1 and MIP-1β) were present only in MES patients. Our results indicate that dysregulation of immune response in schizophrenia develops with illness progression or appears as a long-term medication effect. Chemokine alterations are another example of aberrant immune response in schizophrenia patients. Elevated levels of MCP-1 might represent trait markers since these alterations were found in FEP and MES patients. Other chemokine alterations might be the markers of disease progression or might represent medication effects.

Neurovascular Unit Dysfunction and Blood-Brain Barrier Hyperpermeability Contribute to Schizophrenia Neurobiology: A Theoretical Integration of Clinical and Experimental Evidence

Schizophrenia is a psychotic disorder characterized by delusions, hallucinations, negative symptoms, as well as behavioral and cognitive dysfunction. It is a pathoetiologically heterogeneous disorder involving complex interrelated mechanisms that include oxidative stress and neuroinflammation. Neurovascular endothelial dysfunction and blood-brain barrier (BBB) hyperpermeability are established mechanisms in neurological disorders with comorbid psychiatric symptoms such as epilepsy, traumatic brain injury, and Alzheimer's disease. Schizophrenia is frequently comorbid with medical conditions associated with peripheral vascular endothelial dysfunction, such as metabolic syndrome, cardiovascular disease, and diabetes mellitus. However, the existence and etiological relevance of neurovascular endothelial dysfunction and BBB hyperpermeability in schizophrenia are still not well recognized. Here, we review the growing clinical and experimental evidence, indicating that neurovascular endotheliopathy and BBB hyperpermeability occur in schizophrenia patients. We present a theoretical integration of human and animal data linking oxidative stress and neuroinflammation to neurovascular endotheliopathy and BBB breakdown in schizophrenia. These abnormalities may contribute to the cognitive and behavioral symptoms of schizophrenia via several mechanisms involving reduced cerebral perfusion and impaired homeostatic processes of cerebral microenvironment. Furthermore, BBB disruption can facilitate interactions between brain innate and peripheral adaptive immunity, thereby perpetuating harmful neuroimmune signals and toxic neuroinflammatory responses, which can also contribute to the symptoms of schizophrenia. Taken together, these findings support the "mild encephalitis" hypothesis of schizophrenia. If neurovascular abnormalities prove to be etiologically relevant to the neurobiology of schizophrenia, then targeting these abnormalities may represent a promising therapeutic strategy.

Association of Increased Serum ACE Activity with Logical Memory Ability in Type 2 Diabetic Patients with Mild Cognitive Impairment

Background: Angiotensin-converting enzyme (ACE) is involved in the chronic complications of type 2 diabetes mellitus (T2DM) and Alzheimer's disease. This study aimed to assess the pathogenetic roles of ACE and the genetic predisposition of its insertion/deletion (I/D) polymorphism in mild cognitive impairment (MCI) among T2DM patients.

Methods: A total of 210 T2DM patients were enrolled. Among these patients, 116 satisfied the MCI diagnostic criteria and 94 exhibited healthy cognition. The cognitive functions of the patients were extensively assessed. The serum level and activity of ACE were measured via enzyme-linked immunosorbent assay and ultraviolet spectrophotography. The single-nucleotide polymorphisms of I/D gene of ACE were analyzed.

Results: The serum level and activity of ACE in diabetic MCI patients (p = 0.022 and p = 0.008, respectively) were both significantly higher than those in the healthy controls. A significant negative correlation was found between their ACE activity and logical memory test score (LMT) (p = 0.002). Multiple stepwise regression iterated the negative correlation between ACE activity and LMT score (p = 0.035). Although no significant difference was found in the genotype or allele distribution of ACE I/D polymorphism between the groups, the serum levels and activity of ACE were higher in the DD group than in the ID and II groups (p < 0.05).

Conclusions: Serum ACE activity could better predict logical memory in T2DM patients than ACE level. Further investigations on a large population size are necessary to test whether the D-allele of the ACE gene polymorphism is susceptible to memory deterioration.

Peripheral immuno-inflammatory abnormalities in ultra-high risk of developing psychosis

BACKGROUND

Immuno-inflammatory imbalances have been documented in schizophrenia, but very little is known about the immunological changes prior to the onset of disease.

OBJECTIVE

This work aimed to compare serum levels of pro- and anti-inflammatory cytokines in young subjects at ultra-high risk (UHR) of developing psychosis with age- and sex-matched healthy controls.

METHODS

A total of 12 UHR and 16 age- and sex-matched healthy controls (HC) subjects were enrolled in this study. Clinical profile was assessed using the Comprehensive Assessment of At-Risk Mental States (CAARMS), Semi-Structured Clinical Interview for DSM-IV Axis-I (SCID-I) or Kiddie-SADS-Present and Lifetime Version (K-SADS-PL), and Global Assessment of Functioning (GAF) scale. Serum interleukin (IL)-2, IL-4, IL-6, IL-10, tumor necrosis factor (TNF)-α, IFN-γ, and IL-17 were measured by flow cytometry using the Th1/Th2/Th17 cytometric bead array.

RESULTS

Compared with the healthy control group, patients in UHR showed increased IL-6 levels (Z=-2.370, p=0.018) and decreased IL-17 levels in serum (Z=-1.959, p=0.050). Levels of IL-17 positively correlated to the values in GAF symptoms (rho=0.632, p=0.028).

CONCLUSION

Our results suggest that immunological imbalances could be present in the early stages of psychosis, including in at-risk stages. Future studies should replicate and expand these results.

Genome-wide investigation of schizophrenia associated plasma Ndel1 enzyme activity

Ndel1 is a DISC1-interacting oligopeptidase that cleaves in vitro neuropeptides as neurotensin and bradykinin, and which has been associated with both neuronal migration and neurite outgrowth. We previously reported that plasma Ndel1 enzyme activity is lower in patients with schizophrenia (SCZ) compared to healthy controls (HCs). To our knowledge, no previous study has investigated the genetic factors associated with the plasma Ndel1 enzyme activity. In the current analyses, samples from 83 SCZ patients and 92 control subjects that were assayed for plasma Ndel1 enzyme activity were genotyped on Illumina Omni Express arrays. A genetic relationship matrix using genome-wide information was then used for ancestry correction, and association statistics were calculated genome-wide. Ndel1 enzyme activity was significantly lower in patients with SCZ (t=4.9; p<0.001) and was found to be associated with CAMK1D, MAGI2, CCDC25, and GABGR3, at a level of suggestive significance (p<10(-6)), independent of the clinical status. Then, we performed a model to investigate the observed differences for case/control measures. 2 SNPs at region 1p22.2 reached the p<10(-7) level. ZFPM2 and MAD1L1 were the only two genes with more than one hit at 10(-6) order of p value. Therefore, Ndel1 enzyme activity is a complex trait influenced by many different genetic variants that may contribute to SCZ physiopathology.