A critical role for Macrophage-derived Cysteinyl-Leukotrienes in HIV-1 induced neuronal injury.

Macrophages (MΦ) infected with human immunodeficiency virus (HIV)-1 or activated by its envelope protein gp120 exert neurotoxicity. We found previously that signaling via p38 mitogen-activated protein kinase (p38 MAPK) is essential to the neurotoxicity of HIVgp120-stimulated MΦ. However, the associated downstream pathways remained elusive. Here we show that cysteinyl-leukotrienes (CysLT) released by HIV-infected or HIVgp120 stimulated MΦ downstream of p38 MAPK critically contribute to neurotoxicity. SiRNA-mediated or pharmacological inhibition of p38 MAPK deprives MΦ of CysLT synthase (LTC4S) and, pharmacological inhibition of the cysteinyl-leukotriene receptor 1 (CYSLTR1) protects cerebrocortical neurons against toxicity of both gp120-stimulated and HIV-infected MΦ. Components of the CysLT pathway are differentially regulated in brains of HIV-infected individuals and a transgenic mouse model of NeuroHIV (HIVgp120tg). Moreover, genetic ablation of LTC4S or CysLTR1 prevents neuronal damage and impairment of spatial memory in HIVgp120tg mice. Altogether, our findings suggest a novel critical role for cysteinyl-leukotrienes in HIV-associated brain injury.

CXCL12-induced neurotoxicity critically depends on NMDA receptor-gated and L-type Ca2+ channels upstream of p38 MAPK.

BACKGROUND: The chemokine receptor CXCR4 (CD184) and its natural ligand CXCL12 contribute to many physiological processes, including decisions about cell death and survival in the central nervous system. In addition, CXCR4 is a co-receptor for human immunodeficiency virus (HIV)-1 and mediates the neurotoxicity of the viral envelope protein gp120. However, we previously observed that CXCL12 also causes toxicity in cerebrocortical neurons but the cellular mechanism remained incompletely defined. METHODS: Primary neuronal-glial cerebrocortical cell cultures from rat were exposed to a neurotoxicity-inducing CXCL12 concentration for different times and the activity of the stress-associated mitogen-activated protein kinase p38 (p38 MAPK) was assessed using an in vitro kinase assay. Neurotoxicity of CXCL12 and cellular localization of p38 MAPK was analyzed by immunofluorescence microscopy. Pharmacological inhibition of NMDA-type glutamate receptor-gated ion channels (NMDAR) of L-type Ca2+ channels was employed during 12- and 24-h exposure to neurotoxic amounts of CXCL12 to study the effects on active p38 MAPK and neuronal survival by Western blotting and microscopy, respectively. Neurotoxicity of CXCL12 was also assessed during pharmacological inhibition of p38 MAPK. RESULTS: Here, we show that a neurotoxic amount of CXCL12 triggers a significant increase of endogenous p38 MAPK activity in cerebrocortical cells. Immunofluorescence and Western blotting experiments with mixed neuronal-glial and neuron-depleted glial cerebrocortical cells revealed that the majority of active/phosphorylated p38 MAPK was located in neurons. Blockade of NMDAR-gated ion channels or L-type Ca2+ channels both abrogated an increase of active p38 MAPK and toxicity of CXCL12 in cerebrocortical neurons. Inhibition of L-type Ca2+ channels with nimodipine kept the active kinase at levels not significantly different from baseline while blocking NMDAR with MK-801 strongly reduced phosphorylated p38 MAPK below baseline. Finally, we confirmed that directly blocking p38 MAPK also abrogated neurotoxicity of CXCL12. CONCLUSIONS: Our findings link CXCL12-induced neuronal death to the regulation of NMDAR-gated ion channels and L-type Ca2+ channels upstream of p38 MAPK activation.

CCR5 knockout prevents neuronal injury and behavioral impairment induced in a transgenic mouse model by a CXCR4-using HIV-1 glycoprotein 120.

The innate immune system has been implicated in several neurodegenerative diseases, including HIV-1-associated dementia. In this study, we show that genetic ablation of CCR5 prevents microglial activation and neuronal damage in a transgenic model of HIV-associated brain injury induced by a CXCR4-using viral envelope gp120. The CCR5 knockout (KO) also rescues spatial learning and memory in gp120-transgenic mice. However, the CCR5KO does not abrogate astrocytosis, indicating it can occur independently from neuronal injury and behavioral impairment. To characterize further the neuroprotective effect of CCR5 deficiency we performed a genome-wide gene expression analysis of brains from HIVgp120tg mice expressing or lacking CCR5 and nontransgenic controls. A comparison with a human brain microarray study reveals that brains of HIVgp120tg mice and HIV patients with neurocognitive impairment share numerous differentially regulated genes. Furthermore, brains of CCR5 wild-type and CCR5KO gp120tg mice express markers of an innate immune response. One of the most significantly upregulated factors is the acute phase protein lipocalin-2 (LCN2). Using cerebrocortical cell cultures, we find that LCN2 is neurotoxic in a CCR5-dependent fashion, whereas inhibition of CCR5 alone is not sufficient to abrogate neurotoxicity of a CXCR4-using gp120. However, the combination of pharmacologic CCR5 blockade and LCN2 protects neurons from toxicity of a CXCR4-using gp120, thus recapitulating the finding in CCR5-deficient gp120tg mouse brain. Our study provides evidence for an indirect pathologic role of CCR5 and a novel protective effect of LCN2 in combination with inhibition of CCR5 in HIV-associated brain injury.

Second-Line Pharmaceutical Treatments for Patients with Type 2 Diabetes.

Importance: Assessing the relative effectiveness and safety of additional treatments when metformin monotherapy is insufficient remains a limiting factor in improving treatment choices in type 2 diabetes. Objective: To determine whether data from electronic health records across the University of California Health system could be used to assess the comparative effectiveness and safety associated with 4 treatments in diabetes when added to metformin monotherapy. Design, Setting, and Participants: This multicenter, new user, multidimensional propensity score-matched retrospective cohort study with leave-one-medical-center-out (LOMCO) sensitivity analysis used principles of emulating target trial. Participants included patients with diabetes receiving metformin who were then additionally prescribed either a sulfonylurea, dipeptidyl peptidase-4 inhibitor (DPP4I), sodium-glucose cotransporter-2 inhibitor (SGLT2I), or glucagon-like peptide-1 receptor agonist (GLP1RA) for the first time and followed-up over a 5-year monitoring period. Data were analyzed between January 2022 and April 2023. Exposure: Treatment with sulfonylurea, DPP4I, SGLT2I, or GLP1RA added to metformin monotherapy. Main Outcomes and Measures: The main effectiveness outcome was the ability of patients to maintain glycemic control, represented as time to metabolic failure (hemoglobin A1c [HbA1c] ≥7.0%). A secondary effectiveness outcome was assessed by monitoring time to new incidence of any of 28 adverse outcomes, including diabetes-related complications while treated with the assigned drug. Sensitivity analysis included LOMCO. Results: This cohort study included 31 852 patients (16 635 [52.2%] male; mean [SD] age, 61.4 [12.6] years) who were new users of diabetes treatments added on to metformin monotherapy. Compared with sulfonylurea in random-effect meta-analysis, treatment with SGLT2I (summary hazard ratio [sHR], 0.75 [95% CI, 0.69-0.83]; I2 = 37.5%), DPP4I (sHR, 0.79 [95% CI, 0.75-0.84]; I2 = 0%), GLP1RA (sHR, 0.62 [95% CI, 0.57-0.68]; I2 = 23.6%) were effective in glycemic control; findings from LOMCO sensitivity analysis were similar. Treatment with SGLT2I showed no significant difference in effectiveness compared with GLP1RA (sHR, 1.26 [95% CI, 1.12-1.42]; I2 = 47.3%; no LOMCO) or DPP4I (sHR, 0.97 [95% CI, 0.90-1.04]; I2 = 0%). Patients treated with DPP4I and SGLT2I had fewer cardiovascular events compared with those treated with sulfonylurea (DPP4I: sHR, 0.84 [95% CI, 0.74-0.96]; I2 = 0%; SGLT2I: sHR, 0.78 [95% CI, 0.62-0.98]; I2 = 0%). Patients treated with a GLP1RA or SGLT2I were less likely to develop chronic kidney disease (GLP1RA: sHR, 0.75 [95% CI 0.6-0.94]; I2 = 0%; SGLT2I: sHR, 0.77 [95% CI, 0.61-0.97]; I2 = 0%), kidney failure (GLP1RA: sHR, 0.69 [95% CI, 0.56-0.86]; I2 = 9.1%; SGLT2I: sHR, 0.72 [95% CI, 0.59-0.88]; I2 = 0%), or hypertension (GLP1RA: sHR, 0.82 [95% CI, 0.68-0.97]; I2 = 0%; SGLT2I: sHR, 0.73 [95% CI, 0.58-0.92]; I2 = 38.5%) compared with those treated with a sulfonylurea. Patients treated with an SGLT2I, vs a DPP4I, GLP1RA, or sulfonylurea, were less likely to develop indicators of chronic hepatic dysfunction (sHR vs DPP4I, 0.68 [95% CI, 0.49-0.95]; I2 = 0%; sHR vs GLP1RA, 0.66 [95% CI, 0.48-0.91]; I2 = 0%; sHR vs sulfonylurea, 0.60 [95% CI, 0.44-0.81]; I2 = 0%), and those treated with a DPP4I were less likely to develop new incidence of hypoglycemia (sHR, 0.48 [95% CI, 0.36-0.65]; I2 = 22.7%) compared with those treated with a sulfonylurea. Conclusions and Relevance: These findings highlight familiar medication patterns, including those mirroring randomized clinical trials, as well as providing new insights underscoring the value of robust clinical data analytics in swiftly generating evidence to help guide treatment choices in diabetes.

Activation of p38 MAPK is required in monocytic and neuronal cells for HIV glycoprotein 120-induced neurotoxicity.

HIV-1 envelope protein gp120 has been implicated in neurotoxin production by monocytic cells (i.e., macrophages and microglia), as well as in the pathogenesis of HIV-1-associated neurocognitive disorders. We previously showed in cerebrocortical cell cultures from rodents containing microglia, astrocytes, and neurons that overall inhibition of p38 MAPK signaling abrogated the neurotoxic effect of HIV-1 gp120. However, the time course of p38 MAPK activation and the contribution of this kinase in the various cell types remained unknown. In this study, we found that active p38 MAPK is required in monocytic lineage cells (i.e., macrophages and microglia) and neuronal cells for HIV gp120-induced neurotoxicity to occur. In cerebrocortical cell cultures, HIV-1 gp120 stimulated a time-dependent overall increase in active p38 MAPK, and the activated kinase was primarily detected in microglia and neurons. Interestingly, increased activation of p38 MAPK and neuronal death in response to gp120 were prevented by prior depletion of microglia or the presence of CCR5 ligand CCL4 or p38 MAPK inhibitors. In human monocytic THP-1 cells and primary monocyte-derived macrophages, HIV gp120-stimulated production of neurotoxins was abrogated by prior introduction into the cells of a dominant-negative p38 MAPK mutant or p38 MAPK small interfering RNA. In addition, the neurotoxic effects of cell-free supernatants from gp120-stimulated monocytic THP-1 cells were prevented in microglia-depleted cerebrocortical cells pretreated with a pharmacological inhibitor of p38 MAPK. Thus, p38 MAPK signaling was critical, upon exposure to HIV gp120, for the neurotoxic phenotype of monocytic cells and subsequent toxin-initiated neuronal apoptosis.

Genetic knockouts suggest a critical role for HIV co-receptors in models of HIV gp120-induced brain injury.

Infection with HIV-1 frequently affects the brain and causes NeuroAIDS prior to the development of overt AIDS. The HIV-1 envelope protein gp120 interacts with host CD4 and chemokine co-receptors to initiate infection of macrophages and lymphocytes. In addition, the virus or fragments of it, such as gp120, cause macrophages to produce neurotoxins and trigger neuronal injury and apoptosis. Moreover, the two major HIV co-receptors, the chemokine receptors CCR5 and CXCR4, serve numerous physiological functions and are widely expressed beyond immune cells, including cells in the brain. Therefore, HIV co-receptors are poised to play a direct and indirect part in the development of NeuroAIDS. Although rodents are not permissive to infection with wild type HIV-1, viral co-receptors - more than CD4 - are highly conserved between species, suggesting the animals can be suitable models for mechanistic studies addressing effects of receptor-ligand interaction other than infection. Of note, transgenic mice expressing HIV gp120 in the brain share several pathological hallmarks with NeuroAIDS brains. Against this background, we will discuss recently completed or initiated, ongoing studies that utilize HIV co-receptor knockout and viral gp120-transgenic mice as models for in vitro and in vivo experimentation in order to address the potential roles of HIV gp120 and its co-receptors in the development of NeuroAIDS.

Mitogen-activated protein kinase p38 in HIV infection and associated brain injury.

Infection with human immunodeficiency virus-1 (HIV-1) often leads to HIV-associated neurocognitive disorders (HAND) prior to the progression to acquired immunodeficiency syndrome (AIDS). At the cellular level, mitogen-activated protein kinases (MAPK) provide a family of signal transducers that regulate many processes in response to extracellular stimuli and environmental stress, such as viral infection. Recently, evidence has accumulated suggesting that p38 MAPK plays crucial roles in various pathological processes associated with HIV infection, ranging from macrophage activation to neurotoxicity and impairment of neurogenesis to lymphocyte apoptosis. Thus, p38 MAPK, which has generally been linked to stress-related signal transduction, may be an important mediator in the development of AIDS and HAND.