HIV-1 Tat-mediated neurotoxicity in retinal cells

HIV-1 Tat-Mediated Human Müller Glial Cell Senescence Involves Endoplasmic Reticulum Stress and Dysregulated Autophagy

Antiretroviral treatments have notably extended the lives of individuals with HIV and reduced the occurrence of comorbidities, including ocular manifestations. The involvement of endoplasmic reticulum (ER) stress in HIV-1 pathogenesis raises questions about its correlation with cellular senescence or its role in initiating senescent traits. This study investigated how ER stress and dysregulated autophagy impact cellular senescence triggered by HIV-1 Tat in the MIO-M1 cell line (human Müller glial cells). Cells exposed to HIV-1 Tat exhibited increased vimentin expression combined with markers of ER stress (BiP, p-eIF2α), autophagy (LC3, Beclin-1, p62), and the senescence marker p21 compared to control cells. Western blotting and staining techniques like SA-β-gal were employed to examine these markers. Additionally, treatments with ER stress inhibitor 4-PBA before HIV-1 Tat exposure led to a decreased expression of ER stress, senescence, and autophagy markers. Conversely, pre-treatment with the autophagy inhibitor 3-MA resulted in reduced autophagy and senescence markers but did not alter ER stress markers compared to control cells. The findings suggest a link between ER stress, dysregulated autophagy, and the initiation of a senescence phenotype in MIO-M1 cells induced by HIV-1 Tat exposure.

Immune recovery uveitis: a focus review

Immune recovery uveitis (IRU) is an intraocular inflammation that typically occurs as part of immune reconstitution inflammatory syndrome (IRIS) in the eye. Typically, it affects human immunodeficiency virus (HIV)-infected patients with recognized or unrecognized cytomegalovirus (CMV) retinitis who are receiving highly active antiretroviral therapy (HAART). IRU is a common cause of new vision loss in these patients, and it manifests with a wide range of symptoms and an increased risk of inflammatory complications, such as macular edema. Recently, similar IRU-like responses have been observed in non-HIV individuals with immune reconstitution following immunosuppression of diverse etiologies, posing challenges in diagnosis and treatment. This review provides an updated overview of the current literature on the epidemiology, pathophysiology, biomarkers, clinical manifestations, diagnosis, differential diagnosis, and treatment strategies for IRU.

Mechanisms of Blood-Retinal Barrier Disruption by HIV-1

It has been found that human immunodeficiency virus (HIV)-1 RNA or antigens can be detected in the intraocular tissues of HIV-1 patients even under effective highly active anti-retroviral therapy (HAART). In vivo, blood-retinal barrier (BRB) establishes a critical, physiological guardian against microbial invasion of the eye, but may be compromised in the presence of HIV-1. The envelope glycoprotein gp120 is exposed on the surface of the HIV envelope, essential for virus entry into cells by the attachment to specific cell surface receptors. The BRB disruption by glycoprotein gp120 has been widely recognized, which is toxic to human retinal epithelial cells (RPE) and umbilical vein endothelial cells (HUVEC). The present review elaborates on various mechanisms of BRB disruption induced by HIV gp120, which may represent potential targets for the prevention of ocular HIV complications in the future.

Transgenic mice expressing HIV-1 envelope protein gp120 in the brain as an animal model in neuroAIDS research

HIV-1 infection causes injury to the central nervous system (CNS) and is often associated with neurocognitive disorders. One model for brain damage seen in AIDS patients is the transgenic (tg) mouse expressing a soluble envelope protein gp120 of HIV-1 LAV in the brain in astrocytes under the control of the promoter of glial fibrillary acidic protein. These GFAP-gp120tg mice manifest several key neuropathological features observed in AIDS brains, such as decreased synaptic and dendritic density, increased numbers of activated microglia, and pronounced astrocytosis. Several recent studies show that brains of GFAP-gp120tg mice and neurocognitively impaired HIV patients share also a significant number of differentially regulated genes, activation of innate immunity and other cellular signaling pathways, disturbed neurogenesis, and learning deficits. These findings support the continued relevance of the GFAP-gp120tg mouse as a useful model to investigate neurodegenerative mechanisms and develop therapeutic strategies to mitigate the consequences associated with HIV infection of the CNS, neuroAIDS, and HAND.

Loss of amplitude of accommodation in pre-presbyopic HIV and AIDS patients under treatment with antiretrovirals

Background: The prevalence of HIV and AIDS is causing an enormous public health burden. Its manifestations spare no organ. Ocular complications are mainly attributed to various opportunistic infections which are directly or indirectly caused by immune deficiency.Purpose and aim: The purpose of this study was to determine the effect of HIV and AIDS on subjective amplitude of accommodation of patients under treatment with antiretrovirals and then to compare their results to those of control subjects.Methods: The study took place over a period of 10 months. A quantitative study was carried out on 58 subjects (29 ± 5.5 years) with HIV and AIDS and 35 (28.67 ± 4.6 years) controls of similar age. Amplitude of accommodation was measured using the subjective Royal Air Force push-up method. The influence of CD4+ cell count was also recorded.Results: People with HIV and AIDS had lower mean amplitude of accommodation (5.69 ± 0.88 D) compared to controls (8.53 ± 1.2 D). The decrease in amplitude of accommodation did not show any correlation with the CD4+ cell count. Lower amplitude of accommodation exists in people living with HIV and AIDS when compared with age-related healthy people.Conclusion: The results suggest that patients with HIV and AIDS on antiretroviral drugs (ARVs) have reduced amplitude of accommodation and might experience presbyopia earlier in life than participants without HIV and AIDS. The reduced amplitude of accommodation could be the initial presentation of HIV infection before the systemic manifestation. The possible causes could be the direct neuronal infection by HIV-1, ARVs use, pathological changes of the lens and ciliary muscle or the sensory component of the visual system. It is unknown whether the reduced amplitude of accommodation occurred prior to antiretroviral therapy or represents an ongoing injury to the eye and visual system by the HIV.

Immune recovery uveitis: pathogenesis, clinical symptoms, and treatment

IRU is the most common form of immune reconstitution inflammatory syndrome in HIV-infected patients with cytomegalovirus retinitis who are receiving highly active antiretroviral therapy (HAART). Among patients with CMV in the HAART era, immune recovery may be associated with a greater number of inflammatory complications, including macular edema and epiretinal membrane formation. Given the range of ocular manifestations of HIV, routine ocular examinations and screening for visual loss are recommended in patients with CD4 counts <50 cells/μL. With the increasing longevity of these patients due to the use of HAART, treatment of IRU may become an issue in the future. The aim of this paper is to review the current literature concerning immune recovery uveitis. The definition, epidemiology, pathophysiology, clinical findings, complications, diagnosis, and treatment are presented.

Review: R28 retinal precursor cells: the first 20 years

The R28 retinal precursor cell line was established 20 years ago, originating from a postnatal day 6 rat retinal culture immortalized with the 12S E1A (NP-040507) gene of the adenovirus in a replication-incompetent viral vector. Since that time, R28 cells have been characterized and used for a variety of in vitro and in vivo studies of retinal cell behavior, including differentiation, neuroprotection, cytotoxicity, and light stimulation, as well as retinal gene expression and neuronal function. While no cell culture is equivalent to the intact eye, R28 cells continue to provide an important experimental system for the study of many retinal processes.

The p38 MAPK NF-κB pathway, not the ERK pathway, is involved in exogenous HIV-1 Tat-induced apoptotic cell death in retinal pigment epithelial cells

The mechanism through which human immunodeficiency virus (HIV) infection causes retinal disease and the loss of vision in AIDS patients remains unknown. The HIV-1 transactivator protein Tat (HIV-1 Tat) plays a pivotal role in the pathogenesis of HIV-1 infection and is often described as pleiotropic at different concentrations. In a previous study, we demonstrated that the HIV-1 Tat protein can disrupt the barrier function of retinal pigment epithelium (RPE) at 100 nM without affecting cell viability. The present study was undertaken to determine if HIV-1 Tat can induce RPE cell death at different concentrations and to determine the mechanism of any observed cell death. The results demonstrated that two RPE cell lines (ARPE-19 and D407) treated with Tat at concentrations of 200 nM and above exhibited reduced growth and apoptosis in a dose- and time-dependent manner. The disruption of mitochondrial outer membrane permeabilisation, the activation of caspase-3/7 and 9, the downregulation of Bcl-2, the upregulation of Bax, and the activation of p38 MAPK, ERK and NF-κB were all observed in HIV-1 Tat-treated RPE cells. When exposed to an inhibitor or transfected with siRNA of p38 MAPK and NF-κB, the level of cell death and deregulation of the expression of the apoptotic protein were attenuated. These effects were not observed with an ERK inhibitor or siRNA. Based on these results, we suggest that the induction of apoptosis by HIV-1 Tat in RPE cells may be mediated by p38 MAPK and NF-κB activation and involve the mitochondrial pathway. Therefore, these pathways may provide clues leading to novel therapeutic approaches for the retinopathy induced by HIV infection.

Human immunodeficiency virus and its effects on the visual system

During the first 15 years of the AIDS epidemic patients experienced a high incidence of blindness due to cytomegalovirus (CMV) retinitis and other severe ocular opportunistic infections. Highly active anti-retroviral therapy, introduced in 1996, dramatically decreased the incidence of CMV retinitis. Though CMV retinitis still causes 40% of vision loss in AIDS patients, other conditions such as immune reconstitution uveitis, cataracts, and a significant othercategory -which most investigators believe is directly due to HIV - comprise the majority of cases. HIV causes vascular abnormalities of the conjunctiva and retina in the majority of AIDS patients, as well as retinitis, anterior and posterior uveitis and vasculitis. HIV frequently causes an optic neuropathy and is responsible for the majority of eye movement disorders among HIV patients. Physicians need to be aware that these problems may be the initial manifestation of HIV infections or a sign of highly active anti-retroviral therapy (HAART) failure. Therefore, patients with identifiable risk factors for AIDS who present with ophthalmologic conditions of unknown etiology should be considered for HIV testing. Finally, anti-retroviral therapy has been reported to cause asymptomatic deposits as well as degenerative conditions of both the anterior and posterior segments of the eye.