Gatekeeper role of 14-3-3tau protein in HIV-1 gp120-mediated apoptosis of human endothelial cells by inactivation of Bad

Curcumin induces apoptosis in lung cancer cells by 14-3-3 protein-mediated activation of Bad

The anticancer effects of curcumin are based on the induction of apoptosis, but the specific mechanisms have not yet been fully elucidated. To address this issue, we investigated the effects of curcumin on the intrinsic apoptosis pathway using mitochondria from A549 cells. Curcumin decreased the levels of 14-3-3 proteins, key molecules that inhibit the activation of proapoptotic factors known as BH3-only proteins (e.g. Bad). Curcumin-induced suppression of 14-3-3 protein levels was associated with reduced cytosolic Bad and elevation of mitochondrial Bad, leading to a drop in the mitochondrial membrane potential. 14-3-3 proteins generally interact with Bad phosphorylated by AKT, thus preventing its translocation to the mitochondria where it can promote cell death. Curcumin not only decreased the expression of 14-3-3 proteins but also promoted Bad dephosphorylation in an AKT-dependent fashion. Our results provide novel evidence for the induction of apoptosis by curcumin at multiple stages of the mitochondrial cascade.

Neural stem cell small extracellular vesicle-based delivery of 14-3-3t reduces apoptosis and neuroinflammation following traumatic spinal cord injury by enhancing autophagy by targeting Beclin-1

Neural stem cell-derived small extracellular vesicles (NSC-sEVs) play an important role in the repair of tissue damage. Our previous in vitro and in vivo studies found that preconditioning with NSC-sEVs promoted the recovery of functional behaviors following spinal cord injury by activating autophagy. However, the underlying mechanisms for such observations remain unclear. In this study, we further explored the mechanisms by which NSC-sEVs repair spinal cord injury via autophagy. We found that NSC-sEVs contain 14-3-3t protein, of which the overexpression or knockdown enhanced and decreased autophagy, respectively. In addition, 14-3-3t overexpression enhanced the anti-apoptotic and anti-inflammatory effects of NSC-sEVs, further promoting functional behavior recovery following spinal cord injury. The overexpression of 14-3-3t was used to further validate the in vivo results through a series of in vitro experiments. Conversely, knockdown of 14-3-3t attenuated the anti-apoptotic and anti-inflammatory effects of NSC-sEVs. Further studies also confirmed that NSC-sEVs increased Beclin-1 expression, with which 14-3-3t interacted and promoted its localization to autophagosome precursors. In this study, we found that NSC-sEVs deliver 14-3-3t, which interacts with Beclin-1 to activate autophagy. Our results indicate that 14-3-3t acts via a newly-discovered mechanism for the activation of autophagy by NSC-sEVs.

The P2X7 Receptor Involved in gp120-Induced Cell Injury in BV2 Microglia

This study was aimed at exploring the effects of P2X7 receptor on BV2 microglia cell injury induced by glycoprotein gp120 (gp120) and its underlying mechanisms. We used the MTS method to study the influence of different gp120 concentrations on BV2 microglia cells, and to test the degree of cell injury in each gp120 treatment group; quantitative real-time PCR (qPCR) and Western blot were used to detect the P2X7 mRNA and receptor protein expressions. Immunocytochemistry and Western blot were used to detect the P2X7 receptor expression and P65 NF-κB, respectively. We also measured the content of TNFα, IL-1β, nitric oxide (NO) and reactive oxygen species (ROS). We found that the cell survival rate generally decreased as gp120 concentration increased, and the cell survival rate of the gp120 + Brilliant Blue G (BBG) group was higher than that of the gp120 group. Western blot and qPCR results showed that the expressions of P2X7 receptor protein and mRNA were positively dose-dependent with gp120 concentration; the results of immunocytochemistry and Western blot showed that the expressions of P2X7 receptor and P65 NF-κB in the gp120 group increased significantly compared to those of the control (Ctrl) group, but those in the gp120+BBG group decreased. Taken together, these results confirmed that the P2X7 receptor is involved in gp120-induced BV2 microglial cell injury and that the underlying mechanism may be associated with the over-activation of microglia caused by P2X7 receptor up-regulation, which leads to abundant release of inflammatory factors which exert toxic effects on the cells.

Ibuprofen enhances the anticancer activity of cisplatin in lung cancer cells by inhibiting the heat shock protein 70

Hsp70 is often overexpressed in cancer cells, and the selective cellular survival advantage that it confers may contribute to the process of tumour formation. Thus, the pharmacological manipulation of Hsp70 levels in cancer cells may be an effective means of preventing the progression of tumours. We found that the downregulation of Hsp70 by ibuprofen in vitro enhances the antitumoural activity of cisplatin in lung cancer. Ibuprofen prominently suppressed the expression of Hsp70 in A549 cells derived from lung adenocarcinoma and sensitized them to cisplatin in association with an increase in the mitochondrial apoptotic cascade, whereas ibuprofen alone did not induce cell death. The cisplatin-dependent events occurring up- and downstream of mitochondrial disruption were accelerated by treatment with ibuprofen. The increase in cisplatin-induced apoptosis caused by the depletion of Hsp70 by RNA interference is evidence that the increased apoptosis by ibuprofen is mediated by its effect on Hsp70. Our observations indicate that the suppression of Hsp70 by ibuprofen mediates the sensitivity to cisplatin by enhancing apoptosis at several stages of the mitochondrial cascade. Ibuprofen, therefore, is a potential therapeutic agent that might allow lowering the doses of cisplatin and limiting the many challenge associated with its toxicity and development of drug resistance.

HIV envelope protein gp120-induced apoptosis in lung microvascular endothelial cells by concerted upregulation of EMAP II and its receptor, CXCR3

Chronic lung diseases, such as pulmonary emphysema, are increasingly recognized complications of infection with the human immunodeficiency virus (HIV). Emphysema in HIV may occur independent of cigarette smoking, via mechanisms that are poorly understood but may involve lung endothelial cell apoptosis induced by the HIV envelope protein gp120. Recently, we have demonstrated that lung endothelial apoptosis is an important contributor to the development of experimental emphysema, via upregulation of the proinflammatory cytokine endothelial monocyte-activating polypeptide II (EMAP II) in the lung. Here we investigated the role of EMAP II and its receptor, CXCR3, in gp120-induced lung endothelial cell apoptosis. We could demonstrate that gp120 induces a rapid and robust increase in cell surface expression of EMAP II and its receptor CXCR3. This surface expression occurred via a mechanism involving gp120 signaling through its CXCR4 receptor and p38 MAPK activation. Both EMAP II and CXCR3 were essentially required for gp120-induced apoptosis and exposures to low gp120 concentrations enhanced the susceptibility of endothelial cells to undergo apoptosis when exposed to soluble cigarette smoke extract. These data indicate a novel mechanism by which HIV infection causes endothelial cell loss involved in lung emphysema formation, independent but potentially synergistic with smoking, and suggest therapeutic targets for emphysema prevention and/or treatment.

14-3-3s are potential biomarkers for HIV-related neurodegeneration

Over the last decade, it has become evident that 14-3-3 proteins are essential for primary cell functions. These proteins are abundant throughout the body, including the central nervous system and interact with other proteins in both cell cycle and apoptotic pathways. Examination of cerebral spinal fluid in humans suggests that 14-3-3s including 14-3-3ε (YWHAE) are up-regulated in several neurological diseases, and loss or duplication of the YWHAE gene leads to Miller-Dieker syndrome. The goal of this review is to examine the utility of 14-3-3s as a marker of human immune deficiency virus (HIV)-dependent neurodegeneration and also as a tool to track disease progression. To that end, we describe mechanisms implicating 14-3-3s in neurological diseases and summarize evidence of its interactions with HIV accessory and co-receptor proteins.

Human immunodeficiency virus infection of human astrocytes disrupts blood-brain barrier integrity by a gap junction-dependent mechanism

HIV infection of the CNS is an early event after primary infection, resulting in neurological complications in a significant number of individuals despite antiretroviral therapy (ART). The main cells infected with HIV within the CNS are macrophages/microglia and a small fraction of astrocytes. The role of these few infected astrocytes in the pathogenesis of neuroAIDS has not been examined extensively. Here, we demonstrate that few HIV-infected astrocytes (4.7 ± 2.8% in vitro and 8.2 ± 3.9% in vivo) compromise blood-brain barrier (BBB) integrity. This BBB disruption is due to endothelial apoptosis, misguided astrocyte end feet, and dysregulation of lipoxygenase/cyclooxygenase, BK(Ca) channels, and ATP receptor activation within astrocytes. All of these alterations in BBB integrity induced by a few HIV-infected astrocytes were gap junction dependent, as blocking these channels protected the BBB from HIV-infected astrocyte-mediated compromise. We also demonstrated apoptosis in vivo of BBB cells in contact with infected astrocytes using brain tissue sections from simian immunodeficiency virus-infected macaques as a model of neuroAIDS, suggesting an important role for these few infected astrocytes in the CNS damage seen with HIV infection. Our findings describe a novel mechanism of bystander BBB toxicity mediated by low numbers of HIV-infected astrocytes and amplified by gap junctions. This mechanism of toxicity contributes to understanding how CNS damage is spread even in the current ART era and how minimal or controlled HIV infection still results in cognitive impairment in a large population of infected individuals.

HIV gp120 induces endothelial dysfunction in tumour necrosis factor-alpha-activated porcine and human endothelial cells

AIMS

The aim of this study was to determine direct effects and potential molecular mechanisms of HIV gp120, a viral envelope glycoprotein, on endothelial function.

METHODS AND RESULTS

Fresh porcine coronary artery rings and human coronary artery endothelial cells (HCAECs) were treated with recombinant HIV gp120 for 16 h with or without pretreatment with tumour necrosis factor-alpha (TNF-alpha) (8 h). With a myograph tension analysis, HIV gp120 with TNF-alpha pretreatment significantly decreased endothelium-dependent vasorelaxation in response to bradykinin in porcine coronary artery rings compared with untreated control vessels. In addition, HIV gp120 with TNF-alpha pretreatment significantly reduced endothelial nitric oxide synthase (eNOS) expression-both mRNA and protein levels-in porcine coronary artery rings and HCAECs compared with untreated controls. Furthermore, TNF-alpha pretreatment substantially increased intercellular adhesion molecule-1 (ICAM-1) expression in artery rings and HCAECs. Anti-gp120 or anti-ICAM-1 antibody significantly blocked these effects of HIV gp120. Silencing of ICAM-1 by siRNA oligonucleotides significantly blocked the effect of gp120 on eNOS downregulation in TNF-alpha-pretreated HCAECs.

CONCLUSION

HIV gp120 and TNF-alpha synergistically reduce eNOS expression and cause endothelial dysfunction in both porcine coronary arteries and HCAECs. ICAM-1 induced by TNF-alpha pretreatment may mediate HIV gp120-induced endothelial dysfunction, which suggests a novel molecular mechanism of HIV gp120-ICAM-1 interaction inducing endothelial dysfunction.

Human immunodeficiency virus type 1 gp120-mediated disruption of tight junction proteins by induction of proteasome-mediated degradation of zonula occludens-1 and -2 in human brain microvascular endothelial cells

The infiltration of human immunodeficiency virus (HIV)-1, such as by HIV-infected leukocytes, across an injured blood-brain barrier (BBB) is a characteristic pathologic manifestation of HIV-1-associated dementia. HIV-1 gp120 has been implicated as a cause of breakdown of tight junctions between endothelial cells of the BBB, though the disrupting molecular mechanisms are unexplained. This study offers a new explanation for the increased BBB microvascular permeability, due to the degradation of tight junction proteins by the proteasome induced by gp120, and the negative regulation of this process by the scaffold protein, 14-3-3tau. gp120 reduced the amount of zonula occludens (ZO)-1 and ZO-2 in human brain microvascular endothelial cells (HBMECs). The treatment of HBMECs with the proteasome inhibitor, lactacystin, blocked the degradation of ZO-1 and ZO-2, suggesting that these proteins were targeted by gp120 for degradation by the proteasome. gp120 also specifically increased the expression of 14-3-3tau in HBMECs, and its down-regulation by RNAi facilitated the breakdown of tight junction proteins induced by gp120. Our results demonstrate the novel molecular mechanisms of the BBB breakdown by gp120.