THE EFFECT OF ANTIRETROVIRAL THERAPY ON THE INTEGRATED STRESS RESPONSE IN THE CENTRAL NERVOUS SYSTEM: IN VIVO ASSESSMENT IN SIV-INFECTED RHESUS MACAQUES

Abstract

Despite the benefits of antiretroviral therapy (ART) in people with HIV (PWH), a large percentage of PWH still suffer from some form of neurocognitive impairment. Studies have shown that high degree of oxidative stress and inflammation remain present in the central nervous system of PWH, which can activate the integrated stress response (ISR) pathway. In our lab, studies showed that the levels of several markers for ISR activation, like phosphorylated eukaryotic initiation factor 2α (P-eIF2α), were elevated in neurons and astrocytes in the cortex in autopsy brain tissue of PWH. Phosphorylation of eIF2α is mediated by four kinases, which will result in ISR activation, which is reported in neurodegenerative conditions. In general, ISR is an adaptive pathway; however, chronically activated ISR may contribute to neuronal damage or death and to neurocognitive impairment in PWH. Recently, several studies showed that certain ART drugs contribute to the persistence of HIV-associated neurocognitive disorders and can induce ISR. The aim of the present study was to assess ISR activation in neurons, astrocytes, and oligodendrocytes in brain tissue samples of SIV-infected rhesus macaques. Methods We examined necropsy brain tissue specimens of 11 rhesus macaques, including SIV-infected/ART-untreated macaques (n = 3), SIV-infected/ART-treated macaques (n = 4), and uninfected/untreated (n = 4) macaques to determine if ART aggravated ISR activation in the CNS. Formalin-fixed/paraffin-embedded sections of cortical tissue were immunofluorescently stained using an antibody to p-eIF2α to detect the activation of ISR and antibodies against MAP2, GFAP, and ASPA to label neurons, astrocytes, and oligodendrocytes, respectively. Results By semiquantitative analysis of images of stained specimens obtained from the cortex of the frontal lobes of the treated rhesus macaques, we found that ISR activation in neurons was higher in the SIV-infected/ART-treated group compared to the SIV-infected/ART-untreated group, which was statistically significant. However, we did not observe differences in ISR activation in astrocytes and oligodendrocytes among the three groups. Conclusion In our study, we observed a significant increase in ISR activation in neurons in the gray matter of SIV-infected/ART-treated rhesus macaques compared to SIV-infected/ART-untreated rhesus macaques, which we did not observe in astrocytes and oligodendrocytes.