Enhanced autophagy in pulmonary endothelial cells on exposure to HIV-Tat and morphine: Role in HIV-related pulmonary arterial hypertension

Abstract

Intravenous drug use is one of the major risk factors for HIV-infection in HIV-related pulmonary arterial hypertension patients. We previously demonstrated exaggerated pulmonary vascular remodeling with enhanced apoptosis followed by increased proliferation of pulmonary endothelial cells on simultaneous exposure to both opioids and HIV protein(s). Here we hypothesize that the exacerbation of autophagy may be involved in the switching of endothelial cells from an early apoptotic state to later hyperproliferative state. Treatment of human pulmonary microvascular endothelial cells (HPMECs) with both the HIV-protein Tat and morphine resulted in an oxidative stress-dependent increase in the expression of various markers of autophagy and formation of autophagosomes when compared to either Tat or morphine monotreatments as demonstrated by western blot, transmission electron microscopy and immunofluorescence. Autophagy flux experiments suggested increased formation rather than decreased clearance of autolysosomes. Inhibition of autophagy resulted in a significant increase in apoptosis and reduction in proliferation of HPMECs with combined morphine and Tat (MCT) treatment compared to monotreatments whereas stimulation of autophagy resulted in opposite effects. Significant increases in the expression of autophagy markers as well as the number of autophagosomes and autolysosomes was observed in the lungs of SIV-infected macaques and HIV-infected humans exposed to opioids. Overall our findings indicate that morphine in combination with viral protein(s) results in the induction of autophagy in pulmonary endothelial cells that may lead to an increase in severity of angio-proliferative remodeling of the pulmonary vasculature on simian and human immunodeficiency virus infection in the presence of opioids.

Morphine-Mediated Brain Region-Specific Astrocytosis Involves the ER Stress-Autophagy Axis

“…It has also been reported that exposure of human pulmonary microvascular endothelial cells to both the HIV-1 Tat protein and morphine resulted in an oxidative stress-dependent increased expression of autophagy markers and increased generation of autophagosomes compared to cells exposed to either agent alone. Intriguingly, treatment of these cells with morphine alone or in combination with HIV-1 Tat inhibited the fusion of autophagosome with the lysosomes [66]. Induction of autophagy by morphine is cell-type specific.…”

The role of HIV Tat protein in HIV-related cardiovascular diseases

“…However, chronic increase in autophagy reduces the incidence of oxidative stress and apoptosis that allows the cells to adapt to stress leading to cell survival and uncontrolled proliferation of pulmonary endothelial cells. Therefore, morphine in combination with Tat results in the induction of autophagy in pulmonary endothelial cells that may lead to an increase in severity of angio-proliferative remodeling of the pulmonary vasculature [ 56 ].…”

Escalating morphine dosing in HIV-1 Tat transgenic mice with sustained Tat exposure reveals an allostatic shift in neuroinflammatory regulation accompanied by increased neuroprotective non-endocannabinoid lipid signaling molecules and amino acids

“…Since the inception of cART, the impact of chronic inflammatory insult by HIV-1 infection has become an important topic; persistent latently and productively infected perivascular macrophage and microglial populations [ 14 , 17 – 19 ] represent the primary reservoirs for HIV-1 in the CNS [ 20 – 24 ]. In vivo and in vitro studies focusing on the HIV-1 transactivator of transcription (Tat) protein demonstrate morphine’s exacerbating effects on microglial activation [ 25 – 29 ], astroglia dysregulation [ 29 – 32 ], cytokine production [ 33 – 38 ], and blood-brain barrier (BBB) breakdown [ 13 , 39 , 40 ], with additional effects on oxidative stress [ 33 , 34 , 41 , 42 ], intracellular calcium [ 34 , 37 , 43 ], and neurotoxicity [ 38 , 42 – 44 ], potentially due to morphine’s action on μ-opioid receptor (MOR)-expressing glia [ 31 , 45 ]. Notably, HIV-1 and HIV-1 proteins, such as Tat, impact opioid gene expression and splicing specificity [ 38 , 46 – 48 ], potentially mediated through the release of various proinflammatory cytokines, including IL-6, TNF, GM-CSF, and IFN-γ [ 49 , 50 ].…”