Production and Roles of Glial Tissue Inhibitor of Metalloproteinases-1 in Human Immunodeficiency Virus-1-Associated Dementia Neuroinflammation: A Review

Risk of Parkinson's disease in hepatitis B and C populations: a systematic review and meta-analysis

Parkinson's disease (PD) is a common neurodegenerative disorder, and its association with viral hepatitis has been debated. We performed a meta-analysis to examine the association between PD risk and viral hepatitis. Medline, EMBASE, and the Cochrane library were searched from inception till July 2022. Meta-analysis was conducted using a fixed-effect model with the inverse variance method. Three groups were compared to controls: infection with either hepatitis B or C virus (HBV and HCV, respectively), or coinfection with both viruses. We found 551 records, and six studies comprising of 2,566,947 patients were included in the analysis. PD risk was increased in HCV-infected population (OR 1.10, 95% CI 1.03-1.17, p = 0.005) and (HR 1.37, 95% CI 1.26-1.49, p < 0.001). This increase was not observed for the HBV-infected and HBV-HCV-coinfected coinfection populations. For pooled OR, the risk was significantly lower in HBV-infected (OR 0.79, 95% CI 0.76-0.83, p < 0.001) but not significantly different in HBV-HCV-coinfected populations (OR 0.96, 95% CI 0.82-1.12, p = 0.57). For pooled HR, the risk was significantly higher in both HBV-infected (HR 1.22, 95% CI 1.14-1.31, p < 0.001) and HBV-HCV-coinfected populations (HR 1.29, 95% CI 1.05-1.58, p = 0.013). We found that the risk of PD was increased in the HCV-infected population, but results were inconsistent in those with HBV and HBV-HCV infections. Our findings provide impetus for further clinical and functional studies to unravel the role of the adaptive immune system in PD.

Hepatitis C Virus-Related Central and Peripheral Nervous System Disorders

Hepatitis C Virus (HCV), despite being a hepatotropic virus, is the causative agent of many systemic disorders, such as vasculitis, autoimmune diseases, lymphoproliferative disorders, and a broad spectrum of neurological and psychiatric manifestations. Although symptoms have been misdiagnosed or underdiagnosed, only recently, evidence of direct (inflammatory) or indirect (immune-mediated) HCV-dependent cerebral effects has been established. HCV infection can promote acute inflammatory response, pro-coagulative status and ischemic disorders, and neurodegeneration. These effects rely on cerebral HCV replication, possibly mediated by blood-brain barrier alterations. Further study is needed to better understand the HCV-related mechanisms of brain damage.

Methamphetamine Increases the Proportion of SIV-Infected Microglia/Macrophages, Alters Metabolic Pathways, and Elevates Cell Death Pathways: A Single-Cell Analysis

Both substance use disorder and HIV infection continue to affect many individuals. Both have untoward effects on the brain, and the two conditions often co-exist. In the brain, macrophages and microglia are infectable by HIV, and these cells are also targets for the effects of drugs of abuse, such as the psychostimulant methamphetamine. To determine the interaction of HIV and methamphetamine, we isolated microglia and brain macrophages from SIV-infected rhesus monkeys that were treated with or without methamphetamine. Cells were subjected to single-cell RNA sequencing and results were analyzed by statistical and bioinformatic analysis. In the animals treated with methamphetamine, a significantly increased proportion of the microglia and/or macrophages were infected by SIV. In addition, gene encoding functions in cell death pathways were increased, and the brain-derived neurotropic factor pathway was inhibited. The gene expression patterns in infected cells did not cluster separately from uninfected cells, but clusters comprised of microglia and/or macrophages from methamphetamine-treated animals differed in neuroinflammatory and metabolic pathways from those comprised of cells from untreated animals. Methamphetamine increases CNS infection by SIV and has adverse effects on both infected and uninfected microglia and brain macrophages, highlighting the dual and interacting harms of HIV infection and drug abuse on the brain.

Tissue inhibitor of metalloproteinases 1 enhances rod survival in the rd1 mouse retina

Retinitis pigmentosa (RP), an inherited retinal degenerative disease, is characterized by a progressive loss of rod photoreceptors followed by loss of cone photoreceptors. Previously, when tissue inhibitor of metalloproteinase 1 (TIMP1), a key extracellular matrix (ECM) regulator that binds to and inhibits activation of Matrix metallopeptidase 9 (MMP9) was intravitreal injected into eyes of a transgenic rhodopsin rat model of RP, S334ter-line3, we discovered cone outer segments are partially protected. In parallel, we reported that a specific MMP9 and MMP2 inhibitor, SB-3CT, interferes with mechanisms leading to rod photoreceptor cell death in an MMP9 dependent manner. Here, we extend our initial rat studies to examine the potential of TIMP1 as a treatment in retinal degeneration by investigating neuroprotective effects in a classic mouse retinal degeneration model, rdPde6b-/- (rd1). The results clearly demonstrate that intravitreal injections of TIMP1 produce extended protection to delay rod photoreceptor cell death. The mean total number of rods in whole-mount retinas was significantly greater in TIMP-treated rd1 retinas (postnatal (P) 30, P35 (P<0.0001) and P45 (P<0.05) than in saline-treated rd1 retinas. In contrast, SB-3CT did not delay rod cell death, leading us to further investigate alternative pathways that do not involve MMPs. In addition to inducing phosphorylated ERK1/2, TIMP1 significantly reduces BAX activity and delays attenuation of the outer nuclear layer (ONL). Physiological responses using scotopic electroretinograms (ERG) reveal b-wave amplitudes from TIMP1-treated retinas are significantly greater than from saline-treated rd1 retinas (P<0.05). In later degenerative stages of rd1 retinas, photopic b-wave amplitudes from TIMP1-treated rd1 retinas are significantly larger than from saline-treated rd1 retinas (P<0.05). Our findings demonstrate that TIMP1 delays photoreceptor cell death. Furthermore, this study provides new insights into how TIMP1 works in the mouse animal model of RP.

Hepatitis C virus infection and risk of Parkinson's disease: a systematic review and meta-analysis

BACKGROUND/OBJECTIVE

Hepatitis C virus (HCV) infection is one of the most common infections worldwide. Recent epidemiologic studies have suggested that patients with HCV infection might be at an increased risk of Parkinson's disease. However, the data on this relationship remain inconclusive. This meta-analysis was conducted with the aim to summarize all available evidence.

PATIENTS AND METHODS

A literature search was performed using MEDLINE and EMBASE database from inception to May 2017. Studies that reported relative risks, odd ratios (ORs), or hazard ratios comparing the risk of Parkinson's disease among HCV-infected patients versus participants without HCV infection were included. Pooled OR and 95% confidence interval were calculated using a random-effect, generic inverse variance method.

RESULTS

Of 468 studies, five studies with 323 974 participants met our eligibility criteria and were included in the analysis. We found a higher risk of Parkinson's disease among patients with chronic HCV infection compared with participants without HCV infection with the pooled OR of 1.35 (95% confidence interval: 1.19-1.52). The statistical heterogeneity of this study was insignificant (I=3%). The main limitation of this meta-analysis was the limited accuracy of diagnosis in the primary studies as they were coding-based studies.

CONCLUSION

This study demonstrated a higher risk of Parkinson's disease among HCV-infected patients. Further studies are required to clarify how this risk should be addressed in the clinical picture.

Evidence for association between hepatitis C virus and Parkinson's disease

Parkinson's disease (PD) is a globally prevalent neurodegenerative disorder, characterized by progressive neuronal loss in the substantia nigra and formation of Lewy bodies. These pathological characteristics are clinically translated into motor symptoms, such as bradykinesia, rigidity, resting tremors, and postural instability. Emerging data from epidemiological studies suggest a possible association between PD and hepatitis C virus (HCV) infection, which affects up to 71 million individuals worldwide. Preclinical studies have shown that HCV can penetrate and replicate within the brain macrophages and microglial cells, increasing their production of pro-inflammatory cytokines that can directly cause neuronal toxicity. Other studies reported that interferon, previously used to treat HCV infection, can increase the risk of PD through inhibition of the nigrostriatal dopaminergic transmission or induction of neuroinflammation. In this article, we provide a comprehensive review on the possible association between HCV infection and PD and highlight recommendations for further research and practice in this regard.

The oral cavity in leprosy: what clinicians need to know

Leprosy is a chronic infectious disease caused by Mycobacterium leprae, a bacillus that has a tropism for skin and peripheral nerves. Leprosy treatment is based on a multidrug therapy established by the World Health Organization in 1982 and, despite its widespread use, Brazil ranks second worldwide in numbers of cases. Oral involvement in leprosy has been poorly described in the literature, and few studies have shown that although the bacillus is found in mucosa, specific leprosy lesions are rare and affect patients with advanced stages of the disease. This review aimed to assess the literature on oral manifestations in leprosy and the aspects involving oral cavity in leprosy pathogenesis.

HIV-1, methamphetamine and astrocytes at neuroinflammatory Crossroads

As a popular psychostimulant, methamphetamine (METH) use leads to long-lasting, strong euphoric effects. While METH abuse is common in the general population, between 10 and 15% of human immunodeficiency virus-1 (HIV-1) patients report having abused METH. METH exacerbates the severity and onset of HIV-1-associated neurocognitive disorders (HAND) through direct and indirect mechanisms. Repetitive METH use impedes adherence to antiretroviral drug regimens, increasing the likelihood of HIV-1 disease progression toward AIDS. METH exposure also directly affects both innate and adaptive immunity, altering lymphocyte numbers and activity, cytokine signaling, phagocytic function and infiltration through the blood brain barrier. Further, METH triggers the dopamine reward pathway and leads to impaired neuronal activity and direct toxicity. Concurrently, METH and HIV-1 alter the neuroimmune balance and induce neuroinflammation, which modulates a wide range of brain functions including neuronal signaling and activity, glial activation, viral infection, oxidative stress, and excitotoxicity. Pathologically, reactive gliosis is a hallmark of both HIV-1- and METH-associated neuroinflammation. Significant commonality exists in the neurotoxic mechanisms for both METH and HAND; however, the pathways dysregulated in astroglia during METH exposure are less clear. Thus, this review highlights alterations in astrocyte intracellular signaling pathways, gene expression and function during METH and HIV-1 comorbidity, with special emphasis on HAND-associated neuroinflammation. Importantly, this review carefully evaluates interventions targeting astrocytes in HAND and METH as potential novel therapeutic approaches. This comprehensive overview indicates, without a doubt, that during HIV-1 infection and METH abuse, a complex dialog between all neural cells is orchestrated through astrocyte regulated neuroinflammation.

PPAR agonist-mediated protection against HIV Tat-induced cerebrovascular toxicity is enhanced in MMP-9-deficient mice

The strategies to protect against the disrupted blood-brain barrier (BBB) in HIV-1 infection are not well developed. Therefore, we investigated the potential of peroxisome proliferator-activated receptor (PPAR) agonists to prevent enhanced BBB permeability induced by HIV-1-specific protein Tat. Exposure to Tat via the internal carotid artery (ICA) disrupted permeability across the BBB; however, this effect was attenuated in mice treated with fenofibrate (PPARα agonist) or rosiglitazone (PPARγ agonist). In contrast, exposure to GW9662 (PPARγ antagonist) exacerbated Tat-induced disruption of the BBB integrity. Increased BBB permeability was associated with decreased tight junction (TJ) protein expression and activation of ERK1/2 and Akt in brain microvessels; these effects were attenuated by cotreatment with fenofibrate but not with rosiglitazone. Importantly, both PPAR agonists also protected against Tat-induced astrogliosis and neuronal loss. Because disruption of TJ integrity has been linked to matrix metalloproteinase (MMP) activity, we also evaluated Tat-induced effects in MMP-9-deficient mice. Tat-induced cerebrovascular toxicity, astrogliosis, and neuronal loss were less pronounced in MMP-9-deficient mice as compared with wild-type controls and were further attenuated by PPAR agonists. These results indicate that enhancing PPAR activity combined with targeting MMPs may provide effective therapeutic strategies in brain infection by HIV-1.

The role of metal regulatory proteins in brain oxidative stress: a tutorial

The proteins that regulate the metabolism of a metal must also play a role in regulating the redox activity of the metal. Metals are intrinsic to a substantial number of biological processes and the proteins that regulate those activities are also considerable in number. The role these proteins play in a wide range of physiological processes involves them directly and indirectly in a variety of disease processes. Similarly, it may be therapeutically advantageous to pharmacologically alter the activity of these metal containing proteins to influence disease processes. This paper will introduce the reader to a number of important proteins in both metal metabolism and oxidative stress, with an emphasis on the brain. Potential pharmacological targets will be considered.

Tissue inhibitor of metalloproteinases-1 protects human neurons from staurosporine and HIV-1-induced apoptosis: mechanisms and relevance to HIV-1-associated dementia

HIV-1-associated dementia (HAD)-relevant proinflammatory cytokines robustly induce astrocyte tissue inhibitor of metalloproteinases-1 (TIMP-1). As TIMP-1 displays pleotropic functions, we hypothesized that TIMP-1 expression may serve as a neuroprotective response of astrocytes. Previously, we reported that chronically activated astrocytes fail to maintain elevated TIMP-1 expression, and TIMP-1 levels are lower in the brain of HAD patients; a phenomenon that may contribute to central nervous system pathogenesis. Further, the role of TIMP-1 as a neurotrophic factor is incompletely understood. In this study, we report that staurosporine (STS) and HIV-1(ADA) virus, both led to induction of apoptosis in cultured primary human neurons. Interestingly, cotreatment with TIMP-1 protects neurons from apoptosis and reverses neuronal morphological changes induced by these toxins. Further, the anti-apoptotic effect was not observed with TIMP-2 or -3, but was retained in a mutant of the N-terminal TIMP-1 protein with threonine-2 mutated to glycine (T2G) that is deficient in matrix metalloproteinase (MMP)-1, -2 and -3 inhibitory activity. Therefore, the mechanism is specific to TIMP-1 and partially independent of MMP-inhibition. Additionally, TIMP-1 modulates the Bcl-2 family of proteins and inhibits opening of mitochondrial permeability transition pores induced by HIV-1 or STS. Together, these findings describe a novel function, mechanism and direct role of TIMP-1 in neuroprotection, suggesting its therapeutic potential in HAD and possibly in other neurodegenerative diseases.

Plasma gelsolin accumulates in macrophage nodules in brains of simian immunodeficiency virus infected rhesus macaques

Plasma gelsolin (pGSN), an isoform 1, is secreted by various types of cells in the central nervous system (CNS) and periphery, but not by the liver. pGSN circulates in blood and cerebrospinal fluid (CSF); however, its concentration in CSF is approximately twenty times lower than in plasma. It has been shown that several types of cells such as oligodendrocytes, neurons, and/or astrocytes contribute to the overall pool of pGSN in the CNS. Further, it has been postulated that pGSN plays multiple roles during microbial infection and modulates inflammatory responses; however, the exact mechanism of regulation is not known. We previously showed that levels of pGSN in CSF of individuals with advanced neurocognitive impairment due to HIV infection of the brain are decreased. Here, we show that macrophages express significant amounts of pGSN in response to HIV infection in vitro. Using immunohistochemistry of simian immunodeficiency virus infected rhesus monkey brains, we show that increased levels of pGSN are present in macrophage nodules creating locally a high level of this protein within the brain. This may not be reflected by the overall decreased level in the distinct CSF compartment.