HIV influences microtubule associated protein-2: potential marker of HIV-associated neurocognitive disorders

HIV1 gp120 activates microglia via TLR2-nf-κb signaling to up-regulate inflammatory cytokine expression and induce neuropathic pain

HIV associated neuropathic pain (HANP) is a common complication of AIDS. Intrathecal injection of recombinant HIV-1 gp120 in mice is a well-known model. Previous RNA sequencing revealed spinal TLR2 acts as a differentially expressed gene in HANP mice. The spinal TLR2 is involved in HANP, but its role and underlying mechanism remains unclear. In this study the transcription, expression and distribution characteristics of TLR2 in the spinal cord of HANP male mice have been analyzed by qRT-PCR, Western blotting, and immunofluorescent staining. We found that TLR2 expression was upregulated in the spinal dorsal horn and mainly distributed in microglial cells, and blocking TLR2 relieved pain of HANP mice. Following stimulation by gp120 microglial cells upregulate TLR2 expression and become activated. The activation stimulates their differentiation into the M1 type, increasing IL-1β and TNF-α expression while inhibiting IL-10 expression. Silencing the Tlr2 gene slows down the activation, polarization, and secretion of pro-inflammatory factors in microglial cells induced by gp120, and enhances the expression of anti-inflammatory factors. Further analysis of the impact of gp120 on downstream signaling pathways of TLR2 in microglial cells, including NF-κB, MAPK (p38MAPK, ERK, and JNK) and PI3K/AKT, revealed that TLR2-NF-κB signaling plays a crucial role in the activation and polarization of microglial cells by gp120. Activation of NF-κB signaling aggravates pain in HANP mice, while blocking it lightens pain. This data indicates that gp120, through the TLR2-NF-κB signaling, activates spinal microglial cells, promotes the secretion of inflammatory cytokines, leading to HANP. This provides new targets to develop drugs for HANP.

Honokiol hexafluoro confers reversal of neuropathological markers of HIV infection in a murine SCID model

Cognitive impairment remains a persistent challenge in people living with HIV (PWLH) despite antiretroviral therapy (ART) due to ART's inability to eliminate brain HIV. HIV-induced cognitive dysfunction results from immune dysregulation, ongoing neuroinflammation, and the continuous virus presence, collectively contributing to cognitive deficits. Therefore, adjunctive therapies are needed to reduce cerebral HIV reservoirs, mitigate neuroinflammation, and impede cognitive dysfunction progression. Our study focused on Honokiol, known for its anti-inflammatory and neuroprotective properties, in an experimental mouse model simulating HIV-induced cognitive dysfunction. Using Honokiol Hexafluoro (HH), a synthetic analogue, we comprehensively evaluated its potential to ameliorate cognitive dysfunction and cerebral pathology in HIV-associated cognitive dysfunction. Our findings showed that HH treatment effectively reversed HIV-induced cognitive dysfunction, concurrently suppressing astrocyte activation, restoring neuronal dendritic arborization, and reducing microglial activation. Furthermore, HH remodeled the metabolic profile of HIV-infected human monocyte-derived macrophages, resulting in decreased activation and the promotion of a quiescent state in vitro.

Pathogenic mechanisms of human immunodeficiency virus (HIV)-associated pain

Chronic pain is a prevalent neurological complication among individuals living with human immunodeficiency virus (PLHIV) in the post-combination antiretroviral therapy (cART) era. These individuals experience malfunction in various cellular and molecular pathways involved in pain transmission and modulation, including the neuropathology of the peripheral sensory neurons and neurodegeneration and neuroinflammation in the spinal dorsal horn. However, the underlying etiologies and mechanisms leading to pain pathogenesis are complex and not fully understood. In this review, we aim to summarize recent progress in this field. Specifically, we will begin by examining neuropathology in the pain pathways identified in PLHIV and discussing potential causes, including those directly related to HIV-1 infection and comorbidities, such as antiretroviral drug use. We will also explore findings from animal models that may provide insights into the molecular and cellular processes contributing to neuropathology and chronic pain associated with HIV infection. Emerging evidence suggests that viral proteins and/or antiretroviral drugs trigger a complex pathological cascade involving neurons, glia, and potentially non-neural cells, and that interactions between these cells play a critical role in the pathogenesis of HIV-associated pain.

The role of CCR5 in HIV-associated neurocognitive disorders

While combination antiretroviral therapy (cART) has successfully increased the lifespan of individuals infected with HIV, a significant portion of this population remains affected by HIV-associated neurocognitive disorder (HAND). C-C chemokine receptor 5 (CCR5) has been well studied in immune response and as a co-receptor for HIV infection. HIV-infected (HIV⁺) patients experienced mild to significant amelioration of cognitive function when treated with different CCR5 antagonists, including maraviroc and cenicriviroc. Consistent with clinical results, Ccr5 knockout or knockdown rescued cognitive deficits in HIV animal models, with mechanisms of reduced microgliosis and neuroinflammation. Pharmacologic inhibition of CCR5 directly improved cerebral and hippocampal neuronal plasticity and cognitive function. By summarizing the animal and human studies of CCR5 in HIV-associated cognitive deficits, this review aims to provide an overview of the mechanistic role of CCR5 in HAND pathophysiology. This review also discusses the addition of CCR5 antagonists, such as maraviroc, to cART for targeted prevention and treatment of cognitive impairments in patients infected with HIV.

Intraneuronal β-Amyloid Accumulation: Aging HIV-1 Human and HIV-1 Transgenic Rat Brain

The prevalence of HIV-1 associated neurocognitive disorders (HAND) is significantly greater in older, relative to younger, HIV-1 seropositive individuals; the neural pathogenesis of HAND in older HIV-1 seropositive individuals, however, remains elusive. To address this knowledge gap, abnormal protein aggregates (i.e., β-amyloid) were investigated in the brains of aging (>12 months of age) HIV-1 transgenic (Tg) rats. In aging HIV-1 Tg rats, double immunohistochemistry staining revealed abnormal intraneuronal β-amyloid accumulation in the prefrontal cortex (PFC) and hippocampus, relative to F344/N control rats. Notably, in HIV-1 Tg animals, increased β-amyloid accumulation occurred in the absence of any genotypic changes in amyloid precursor protein (APP). Furthermore, no clear amyloid plaque deposition was observed in HIV-1 Tg animals. Critically, β-amyloid was co-localized with neurons in the cortex and hippocampus, supporting a potential mechanism underlying synaptic dysfunction in the HIV-1 Tg rat. Consistent with these neuropathological findings, HIV-1 Tg rats exhibited prominent alterations in the progression of temporal processing relative to control animals; temporal processing relies, at least in part, on the integrity of the PFC and hippocampus. In addition, in post-mortem HIV-1 seropositive individuals with HAND, intraneuronal β-amyloid accumulation was observed in the dorsolateral PFC and hippocampal dentate gyrus. Consistent with observations in the HIV-1 Tg rat, no amyloid plaques were found in these post-mortem HIV-1 seropositive individuals with HAND. Collectively, intraneuronal β-amyloid aggregation observed in the PFC and hippocampus of HIV-1 Tg rats supports a potential factor underlying HIV-1 associated synaptodendritic damage. Further, the HIV-1 Tg rat provides a biological system to model HAND in older HIV-1 seropositive individuals.

Recent Advances in the Molecular and Cellular Mechanisms of gp120-Mediated Neurotoxicity

Axonal degeneration and loss of synapses are often seen in different brain areas of people living with human immunodeficiency virus (HIV). Nevertheless, the underlying causes of the pathological alterations observed in these individuals are poorly comprehended, considering that HIV does not infect neurons. Experimental data have shown that viral proteins, including the envelope protein gp120, cause synaptic pathology followed by neuronal cell death. These neurotoxic effects on synapses could be the result of a variety of mechanisms that decrease synaptic plasticity. In this paper, we will briefly present new emerging concepts connected with the ability of gp120 to promote the degeneration of synapses by either directly damaging the axonal cytoskeleton and/or the indirect activation of the p75 neurotrophin receptor death domain in dendrites.

Reduced neuronal population in the dorsolateral prefrontal cortex in infant macaques infected with simian immunodeficiency virus (SIV)

Pediatric HIV infection remains a global health crisis with an estimated 150,000 new mother-to-child (MTCT) infections each year. Antiretroviral therapy (ART) has improved childhood survival, but only an estimated 53% of children worldwide have access to treatment. Adding to the health crisis is the neurological impact of HIV on the developing brain, in particular cognitive and executive function, which persists even when ART is available. Imaging studies suggest structural, connectivity, and functional alterations in perinatally HIV-infected youth. However, the paucity of histological data limits our ability to identify specific cortical regions that may underlie the clinical manifestations. Utilizing the pediatric simian immunodeficiency virus (SIV) infection model in infant macaques, we have previously shown that early-life SIV infection depletes the neuronal population in the hippocampus. Here, we expand on these previous studies to investigate the dorsolateral prefrontal cortex (dlPFC). A total of 11 ART-naïve infant rhesus macaques (Macaca mulatta) from previous studies were retrospectively analyzed. Infant macaques were either intravenously (IV) inoculated with highly virulent SIVmac251 at ~1 week of age and monitored for 6-10 weeks or orally challenged with SIVmac251 from week 9 of age onwards with a monitoring period of 10-23 weeks post-infection (19-34 weeks of age), and SIV-uninfected controls were euthanized at 16-17 weeks of age. Both SIV-infected groups show a significant loss of neurons along with evidence of ongoing neuronal death. Oral- and IV-infected animals showed a similar neuronal loss which was negatively correlated to chronic viremia levels as assessed by an area under the curve (AUC) analysis. The loss of dlPFC neurons may contribute to the rapid neurocognitive decline associated with pediatric HIV infection.

Soluble Biomarkers of Cognition and Depression in Adults with HIV Infection in the Combination Therapy Era

PURPOSE OF REVIEW

Cognitive impairment and depression continue to be common among people with HIV (PWH) in the combination antiretroviral therapy (ART) era. A better understanding of the biological mechanisms that may underpin these disorders is needed. The purpose of this review is to describe published findings on soluble biomarkers from blood and cerebrospinal fluid (CSF) that have been associated with either cognition or depression among PWH in the setting of ART.

RECENT FINDINGS

Several biomarkers, including those that reflect viral persistence, monocyte/macrophage activation, and other processes, are associated with cognition and depressive symptoms. Some but not all results have been consistent across multiple studies. More research has been published on biomarkers of cognition relative to biomarkers of depression (particularly from CSF). More studies are needed that investigate multiple biomarkers to understand the role of distinct but additive pathways in these disorders and to guide the development of new therapies.

HIV-associated neurotoxicity and cognitive decline: Therapeutic implications

As our understanding of changes to the neurological system has improved, it has become clear that patients who have contracted human immunodeficiency virus type 1 (HIV-1) can potentially suffer from a cascade of neurological issues, including neuropathy, dementia, and declining cognitive function. The progression from mild to severe symptoms tends to affect motor function, followed by cognitive changes. Central nervous system deficits that are observed as the disease progresses have been reported as most severe in later-stage HIV infection. Examining the full spectrum of neuronal damage, generalized cortical atrophy is a common hallmark, resulting in the death of multiple classes of neurons. With antiretroviral therapy (ART), we can partially control disease progression, slowing the onset of the most severe symptoms such as, reducing viral load in the brain, and developing HIV-associated dementia (HAD). HAD is a severe and debilitating outcome from HIV-related neuropathologies. HIV neurotoxicity can be direct (action directly on the neuron) or indirect (actions off-site that affect normal neuronal function). There are two critical HIV-associated proteins, Tat and gp120, which bear responsibility for many of the neuropathologies associated with HAD and HIV-associated neurocognitive disorder (HAND). A cascade of systems is involved in HIV-related neurotoxicity, and determining a critical point where therapeutic strategies can be employed is of the utmost importance. This review will provide an overview of the existing hypotheses on HIV-neurotoxicity and the potential for the development of therapeutics to aid in the treatment of HIV-related nervous system dysfunction.

Co-receptor signaling in the pathogenesis of neuroHIV

The HIV co-receptors, CCR5 and CXCR4, are necessary for HIV entry into target cells, interacting with the HIV envelope protein, gp120, to initiate several signaling cascades thought to be important to the entry process. Co-receptor signaling may also promote the development of neuroHIV by contributing to both persistent neuroinflammation and indirect neurotoxicity. But despite the critical importance of CXCR4 and CCR5 signaling to HIV pathogenesis, there is only one therapeutic (the CCR5 inhibitor Maraviroc) that targets these receptors. Moreover, our understanding of co-receptor signaling in the specific context of neuroHIV is relatively poor. Research into co-receptor signaling has largely stalled in the past decade, possibly owing to the complexity of the signaling cascades and functions mediated by these receptors. Examining the many signaling pathways triggered by co-receptor activation has been challenging due to the lack of specific molecular tools targeting many of the proteins involved in these pathways and the wide array of model systems used across these experiments. Studies examining the impact of co-receptor signaling on HIV neuropathogenesis often show activation of multiple overlapping pathways by similar stimuli, leading to contradictory data on the effects of co-receptor activation. To address this, we will broadly review HIV infection and neuropathogenesis, examine different co-receptor mediated signaling pathways and functions, then discuss the HIV mediated signaling and the differences between activation induced by HIV and cognate ligands. We will assess the specific effects of co-receptor activation on neuropathogenesis, focusing on neuroinflammation. We will also explore how the use of substances of abuse, which are highly prevalent in people living with HIV, can exacerbate the neuropathogenic effects of co-receptor signaling. Finally, we will discuss the current state of therapeutics targeting co-receptors, highlighting challenges the field has faced and areas in which research into co-receptor signaling would yield the most therapeutic benefit in the context of HIV infection. This discussion will provide a comprehensive overview of what is known and what remains to be explored in regard to co-receptor signaling and HIV infection, and will emphasize the potential value of HIV co-receptors as a target for future therapeutic development.