Notch3 deletion regulates HIV-1 gene expression and systemic inflammation to ameliorate chronic kidney disease

Antiretroviral therapy (ART) has profoundly decreased HIV-1 associated morbidity. However, despite ART, immune cells remain latently infected and slowly release viral proteins, leading to chronic inflammation and HIV associated comorbidities. Thus, new strategies are needed to reduce the inflammatory effects of HIV-1. In previous studies we found that gamma secretase inhibitor (GSIXX) ameliorated renal lesions of HIV-Tg26 mice carrying replication defective HIV-1 PNL4-3 by inhibiting Notch activation. Since gamma secretase inhibition is not a safe strategy in humans, here we examined the specific role of the Notch3 pathway in the pathogenesis of the renal lesions and outcome of HIV-Tg26 mice. We found that Notch3 is activated in podocytes and other renal cells in HIV-Tg26 mice and human biopsies with HIV-1 associated Nephropathy (HIVAN). Knockdown of Notch3 in HIV-Tg26 mice revealed a marked reduction in the mortality rate, improvement in renal injury and function. RNA sequencing and immunolabeling data revealed that Notch3 deletion drastically reduced infiltrating renal macrophages in HIV-Tg-N3KO mice in association with renal reduction of HIV-nef mRNA expression levels. In fact, bone marrow derived macrophages from HIV-Tg26 mice showed a significant activation of Notch3 signaling. Further, systemic levels of TNF-alpha and MCP-1 and other inflammatory chemokines and cytokines were reduced in Tg-N3KO mice as compared to HIV-Tg26 mice and this translated to a marked reduction of HIV-induced skin lesions. Taken together, these studies strongly point to a dual inhibitory/therapeutic effect of Notch3 inhibition on HIV-induced systemic, skin and renal lesions independently of ART.

HIV and Drug Use: A Tale of Synergy in Pulmonary Vascular Disease Development

Over the past two decades, with the advent and adoption of highly active anti-retroviral therapy, HIV-1 infection, a once fatal and acute illness, has transformed into a chronic disease with people living with HIV (PWH) experiencing increased rates of cardio-pulmonary vascular diseases including life-threatening pulmonary hypertension. Moreover, the chronic consequences of tobacco, alcohol, and drug use are increasingly seen in older PWH. Drug use, specifically, can have pathologic effects on the cardiovascular health of these individuals. The "double hit" of drug use and HIV may increase the risk of HIV-associated pulmonary arterial hypertension (HIV-PAH) and potentiate right heart failure in this population. This article explores the epidemiology and pathophysiology of PAH associated with HIV and recreational drug use and describes the proposed mechanisms by which HIV and drug use, together, can cause pulmonary vascular remodeling and cardiopulmonary hemodynamic compromise. In addition to detailing the proposed cellular and signaling pathways involved in the development of PAH, this article proposes areas ripe for future research, including the influence of gut dysbiosis and cellular senescence on the pathobiology of HIV-PAH. © 2023 American Physiological Society. Compr Physiol 13:4659-4683, 2023.

Persistent circulation of soluble and extracellular vesicle-linked Spike protein in individuals with postacute sequelae of COVID-19

SARS-CoV-2, the causative agent of COVID-19 disease, has resulted in the death of millions worldwide since the beginning of the pandemic in December 2019. While much progress has been made to understand acute manifestations of SARS-CoV-2 infection, less is known about post-acute sequelae of COVID-19 (PASC). We investigated the levels of both Spike protein (Spike) and viral RNA circulating in patients hospitalized with acute COVID-19 and in patients with and without PASC. We found that Spike and viral RNA were more likely to be present in patients with PASC. Among these patients, 30% were positive for both Spike and viral RNA; whereas, none of the individuals without PASC were positive for both. The levels of Spike and/or viral RNA in the PASC+ve patients were found to be increased or remained the same as in the acute phase; whereas, in the PASC-ve group, these viral components decreased or were totally absent. Additionally, this is the first report to show that part of the circulating Spike is linked to extracellular vesicles without any presence of viral RNA in these vesicles. In conclusion, our findings suggest that Spike and/or viral RNA fragments persist in the recovered COVID-19 patients with PASC up to 1 year or longer after acute SARS-CoV-2 infection.

Potential long-term effects of SARS-CoV-2 infection on the pulmonary vasculature: Multilayered cross-talks in the setting of coinfections and comorbidities

The Coronavirus Disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and its sublineages pose a new challenge to healthcare systems worldwide due to its ability to efficiently spread in immunized populations and its resistance to currently available therapies. COVID-19, although targeting primarily the respiratory system, is also now well established that later affects every organ in the body. Most importantly, despite the available therapy and vaccine-elicited protection, the long-term consequences of viral infection in breakthrough and asymptomatic individuals are areas of concern. In the past two years, investigators accumulated evidence on how the virus triggers our immune system and the molecular signals involved in the cross-talk between immune cells and structural cells in the pulmonary vasculature to drive pathological lung complications such as endothelial dysfunction and thrombosis. In the review, we emphasize recent updates on the pathophysiological inflammatory and immune responses associated with SARS-CoV-2 infection and their potential long-term consequences that may consequently lead to the development of pulmonary vascular diseases.

Exploring extracellular vesicles as mediators of clinical disease and vehicles for viral therapeutics: Insights from the COVID-19 pandemic

The COVID-19 pandemic has challenged researchers to rapidly understand the capabilities of the SARS-CoV-2 virus and investigate potential therapeutics for SARS-CoV-2 infection. COVID-19 has been associated with devastating lung and cardiac injury, profound inflammation, and a heightened coagulopathic state, which may, in part, be driven by cellular crosstalk facilitated by extracellular vesicles (EVs). In recent years, EVs have emerged as important biomarkers of disease, and while extracellular vesicles may contribute to the spread of COVID-19 infection from one cell to the next, they also may be engineered to play a protective or therapeutic role as decoys or "delivery drivers" for therapeutic agents. This review explores these roles and areas for future study.

Extracellular Vesicle TGF-β1 Is Linked to Cardiopulmonary Dysfunction in Human Immunodeficiency Virus

Extracellular vesicles (EVs) have emerged as important mediators in cell-cell communication; however, their relevance in pulmonary hypertension (PH) secondary to human immunodeficiency virus (HIV) infection is yet to be explored. Considering that circulating monocytes are the source of the increased number of perivascular macrophages surrounding the remodeled vessels in PH, this study aimed to identify the role of circulating small EVs and EVs released by HIV-infected human monocyte-derived macrophages in the development of PH. We report significantly higher numbers of plasma-derived EVs carrying higher levels of TGF-β1 (transforming growth factor-β1) in HIV-positive individuals with PH compared with individuals without PH. Importantly, levels of these TGF-β1-loaded, plasma-derived EVs correlated with pulmonary arterial systolic pressures and CD4 counts but did not correlate with the Dl CO or viral load. Correspondingly, enhanced TGF-β1-dependent pulmonary endothelial injury and smooth muscle hyperplasia were observed. HIV-1 infection of monocyte-derived macrophages in the presence of cocaine resulted in an increased number of TGF-β1-high EVs, and intravenous injection of these EVs in rats led to increased right ventricle systolic pressure accompanied by myocardial injury and increased levels of serum ET-1 (endothelin-1), TNF-α, and cardiac troponin-I. Conversely, pretreatment of rats with TGF-β receptor 1 inhibitor prevented these EV-mediated changes. Findings define the ability of macrophage-derived small EVs to cause pulmonary vascular modeling and PH via modulation of TGF-β signaling and suggest clinical implications of circulating TGF-β-high EVs as a potential biomarker of HIV-associated PH.

Extracellular vesicle-mediated endothelial apoptosis and EV-associated proteins correlate with COVID-19 disease severity

Coronavirus disease-2019 (COVID-19), caused by the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has lead to a global pandemic with a rising toll in infections and deaths. Better understanding of its pathogenesis will greatly improve the outcomes and treatment of affected patients. Here we compared the inflammatory and cardiovascular disease-related protein cargo of circulating large and small extracellular vesicles (EVs) from 84 hospitalized patients infected with SARS-CoV-2 with different stages of disease severity. Our findings reveal significant enrichment of proinflammatory, procoagulation, immunoregulatory and tissue-remodelling protein signatures in EVs, which remarkably distinguished symptomatic COVID-19 patients from uninfected controls with matched comorbidities and delineated those with moderate disease from those who were critically ill. Specifically, EN-RAGE, followed by TF and IL-18R1, showed the strongest correlation with disease severity and length of hospitalization. Importantly, EVs from COVID-19 patients induced apoptosis of pulmonary microvascular endothelial cells in the order of disease severity. In conclusion, our findings support a role for EVs in the pathogenesis of COVID-19 disease and underpin the development of EV-based approaches to predicting disease severity, determining need for patient hospitalization and identifying new therapeutic targets.

Impact of human immunodeficiency virus on pulmonary vascular disease

With the advent of anti-retroviral therapy, non-AIDS-related comorbidities have increased in people living with HIV. Among these comorbidities, pulmonary hypertension (PH) is one of the most common causes of morbidity and mortality. Although chronic HIV-1 infection is independently associated with the development of pulmonary arterial hypertension, PH in people living with HIV may also be the outcome of various co-morbidities commonly observed in these individuals including chronic obstructive pulmonary disease, left heart disease and co-infections. In addition, the association of these co-morbidities and other risk factors, such as illicit drug use, can exacerbate the development of pulmonary vascular disease. This review will focus on these complex interactions contributing to PH development and exacerbation in HIV patients. We also examine the interactions of HIV proteins, including Nef, Tat, and gp120 in the pulmonary vasculature and how these proteins alter the endothelial and smooth muscle function by transforming them into susceptible PH phenotype. The review also discusses the available infectious and non-infectious animal models to study HIV-associated PAH, highlighting the advantages and disadvantages of each model, along with their ability to mimic the clinical manifestations of HIV-PAH.

The Potential Role of Extracellular Vesicles in COVID-19 Associated Endothelial injury and Pro-inflammation

COVID-19 infection caused by the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has resulted in a global pandemic with the number of deaths growing exponentially. Early evidence points to significant endothelial dysfunction, micro-thromboses, pro-inflammation as well as a dysregulated immune response in the pathogenesis of this disease. In this study, we analyzed the cargo of EVs isolated from the plasma of patients with COVID-19 for the identification of potential biomarkers of disease severity and to explore their role in disease pathogenesis. Plasma-derived EVs were isolated from 53 hospitalized patients with COVID infection and compared according to the severity of the disease. Analysis of inflammatory and cardiovascular protein cargo of large EVs revealed significantly differentially expressed proteins for each disease sub-group. Notably, members of the TNF superfamily and IL-6 family were up-regulated in patients on oxygen support with severe and moderate disease. EVs from the severe group were also enhanced with pro-thrombotic/endothelial injury factors (TF, t-PA, vWF) and proteins associated with cardiovascular pathology (MB, PRSS8, REN, HGF). Significantly higher levels of TF, CD163, and EN-RAGE were observed in EVs from severe patients when compared to patients with a moderate disease requiring supplemental O2. Importantly, we also observed increased caspase 3/7 activity and decreased cell survival in human pulmonary microvascular endothelial cells exposed to EVs from the plasma of patients with severe disease compared to healthy controls. In conclusion, our findings indicate alterations in pro-inflammatory, coagulopathy, and endothelial injury protein cargo in large EVs in response to SARS-CoV-2 infection that may be a causative agent in severe illness.

Extracellular vesicles: novel communicators in lung diseases

The lung is the organ with the highest vascular density in the human body. It is therefore perceivable that the endothelium of the lung contributes significantly to the circulation of extracellular vesicles (EVs), which include exosomes, microvesicles, and apoptotic bodies. In addition to the endothelium, EVs may arise from alveolar macrophages, fibroblasts and epithelial cells. Because EVs harbor cargo molecules, such as miRNA, mRNA, and proteins, these intercellular communicators provide important insight into the health and disease condition of donor cells and may serve as useful biomarkers of lung disease processes. This comprehensive review focuses on what is currently known about the role of EVs as markers and mediators of lung pathologies including COPD, pulmonary hypertension, asthma, lung cancer and ALI/ARDS. We also explore the role EVs can potentially serve as therapeutics for these lung diseases when released from healthy progenitor cells, such as mesenchymal stem cells.

NADPH oxidase-mediated endothelial injury in HIV- and opioid-induced pulmonary arterial hypertension

We previously demonstrated that the combined exposure of human pulmonary microvascular endothelial cells (HPMECs) to morphine and viral protein(s) results in the oxidative stress-mediated induction of autophagy, leading to shift in the cells from early apoptotic to apoptosis-resistant proliferative status associated with the angioproliferative remodeling observed in pulmonary arterial hypertension (PAH). In this study, we tried to delineate the major source of HIV-1 protein Tat and morphine induced oxidative burst in HPMECs and its consequences on vascular remodeling and PAH in an in vivo model. We observed switch from the initial increased expression of NADPH oxidase (NOX) 2 in response to acute treatment of morphine and HIV-Tat to later increased expression of NOX4 on chronic treatment in the endoplasmic reticulum of HPMECs without any alterations in the mitochondria. Furthermore, NOX-dependent induction of autophagy was observed to play a pivotal role in regulating the endothelial cell survival. Our in vivo findings showed significant increase in pulmonary vascular remodeling, right ventricular systolic pressure, and Fulton index in HIV-transgenic rats on chronic administration of morphine. This was associated with increased oxidative stress in lung tissues and rat pulmonary microvascular endothelial cells. Additionally, endothelial cells from morphine-treated HIV-transgenic rats demonstrated increased expression of NOX2 and NOX4 proteins, inhibition of which ameliorated their increased survival upon serum starvation. In conclusion, this study describes NADPH oxidases as one of the main players in the oxidative stress-mediated endothelial dysfunction on the dual hit of HIV-viral protein(s) and opioids.

Sugen-morphine model of pulmonary arterial hypertension

Pulmonary arterial hypertension is a fatal disease associated with pulmonary vascular remodeling and right ventricular hypertrophy. Pre-clinical animal models that reproduce the human pulmonary arterial hypertension process and pharmacological response to available therapies are critical for future drug development. The most prevalent animal model reproducing many aspects of angioobliterative forms of pulmonary arterial hypertension is the rat Sugen/hypoxia model in which Sugen, a vascular endothelial growth factor receptor antagonist, primarily causes initiation of endothelial injury and later in the presence of hypoxia promotes proliferation of apoptosis-resistant endothelial cells. We previously demonstrated that exposure of human pulmonary microvascular endothelium to morphine and HIV-proteins results in initial apoptosis followed by increased proliferation. Here, we demonstrate that the double-hit of morphine and Sugen 5416 (Sugen–morphine) in rats leads to the development of pulmonary arterial hypertension with significant medial hypertrophy of pre-acinar pulmonary arteries along with neo-intimal thickening of intra-acinar vessels. In addition, the pulmonary smooth muscle and endothelial cells isolated from Sugen–morphine rats showed hyperproliferation and apoptotic resistance, respectively, in response to serum starvation. Our findings support that the dual hit model of Sugen 5416 and morphine provides another experimental strategy to induce significant pulmonary vascular remodeling and development of severe pulmonary arterial hypertension pathology in rats without exposure to hypoxia.

HIV-Nef Protein Persists in the Lungs of Aviremic Patients with HIV and Induces Endothelial Cell Death

It remains a mystery why HIV-associated end-organ pathologies persist in the era of combined antiretroviral therapy (ART). One possible mechanism is the continued production of HIV-encoded proteins in latently HIV-infected T cells and macrophages. The proapoptotic protein HIV-Nef persists in the blood of ART-treated patients within extracellular vesicles (EVs) and peripheral blood mononuclear cells. Here we demonstrate that HIV-Nef is present in cells and EVs isolated from BAL of patients on ART. We hypothesize that HIV-Nef persistence in the lung induces endothelial apoptosis leading to endothelial dysfunction and further pulmonary vascular pathologies. The presence of HIV-Nef in patients with HIV correlates with the surface expression of the proapoptotic endothelial-monocyte-activating polypeptide II (EMAPII), which was implicated in progression of pulmonary emphysema via mechanisms involving endothelial cell death. HIV-Nef protein induces EMAPII surface expression in human embryonic kidney 293T cells, T cells, and human and mouse lung endothelial cells. HIV-Nef packages itself into EVs and increases the amount of EVs secreted from Nef-expressing T cells and Nef-transfected human embryonic kidney 293T cells. EVs from BAL of HIV⁺ patients and Nef-transfected cells induce apoptosis in lung microvascular endothelial cells by upregulating EMAPII surface expression in a PAK2-dependent fashion. Transgenic expression of HIV-Nef in vascular endothelial-cadherin⁺ endothelial cells leads to lung rarefaction, characterized by reduced alveoli and overall increase in lung inspiratory capacity. These changes occur concomitantly with lung endothelial cell apoptosis. Together, these data suggest that HIV-Nef induces endothelial cell apoptosis via an EMAPII-dependent mechanism that is sufficient to cause pulmonary vascular pathologies even in the absence of inflammation.

Analysis of lncRNA-miRNA-mRNA Interactions in Hyper-proliferative Human Pulmonary Arterial Smooth Muscle Cells

We previously reported enhanced proliferation of smooth muscle cells on the combined exposure of HIV proteins and cocaine leading to the development of HIV-pulmonary arterial hypertension. Here, we attempt to comprehensively understand the interactions between long noncoding RNAs (lncRNAs), mRNAs and micro-RNAs (miRNAs) to determine their role in smooth muscle hyperplasia. Differential expression of lncRNAs, mRNAs and miRNAs were obtained by microarray and small-RNA sequencing from HPASMCs treated with and without cocaine and/or HIV-Tat. LncRNA to mRNA associations were conjectured by analyzing their genomic proximity and by interrogating their association to vascular diseases and cancer co-expression patterns reported in the relevant databases. Neuro-active ligand receptor signaling, Ras signaling and PI3-Akt pathway were among the top pathways enriched in either differentially expressed mRNAs or mRNAs associated to lncRNAs. HPASMC with combined exposure to cocaine and Tat (C + T) vs control identified the following top lncRNA-mRNA pairs, ENST00000495536-HOXB13, T216482-CBL, ENST00000602736-GDF7, and, TCONS_00020413-RND1. Many of the down-regulated miRNAs in the HPASMCs treated with C + T were found to be anti-proliferative and targets of up-regulated lncRNAs targeting up-regulated mRNAs, including down-regulation of miR-185, -491 and up-regulation of corresponding ENST00000585387. Specific knock down of the selected lncRNAs highlighted the importance of non-coding RNAs in smooth muscle hyperplasia.

Macrophage-derived extracellular vesicles mediate smooth muscle hyperplasia: role of altered miRNA cargo in response to HIV infection and substance abuse

Our previous studies consistently demonstrate enhanced pulmonary vascular remodeling in HIV–infected intravenous drug users, and in simian immunodeficiency virus–infected macaques or HIV-transgenic rats exposed to opioids or cocaine. Although we reported an associated increase in perivascular inflammation, the exact role of inflammatory cells in the development of pulmonary vascular remodeling remains unknown. In this study, HIV–infected and cocaine (H+C)–treated human monocyte derived macrophages released a higher number of extracellular vesicles (EVs), compared to HIV-infected or uninfected cocaine-treated macrophages, with a significant increase in the particle size range to 100–150 nm. Treatment of primary human pulmonary arterial smooth muscle cells (HPASMCs) with these EVs resulted in a significant increase in smooth muscle proliferation. We also observed a significant increase in the miRNA-130a level in the EVs derived from H+C-treated macrophages that corresponded with the decrease in the expression of phosphatase and tensin homolog and tuberous sclerosis 1 and 2 and activation of PI3K/protein kinase B signaling in HPASMCs on addition of these EVs. Transfection of HPASMCs with antagomir-130a–ameliorated the EV-induced effect. Thus, we conclude that EVs derived from H+C-treated macrophages promote pulmonary smooth muscle proliferation by delivery of its prosurvival miRNA cargo, which may play a crucial role in the development of PAH.—Sharma, H., Chinnappan, M., Agarwal, S., Dalvi, P., Gunewardena, S., O’Brien-Ladner, A., Dhillon, N. K. Macrophage-derived extracellular vesicles mediate smooth muscle hyperplasia: role of altered miRNA cargo in response to HIV infection and substance abuse.

Network of MicroRNAs Mediate Translational Repression of Bone Morphogenetic Protein Receptor-2: Involvement in HIV-Associated Pulmonary Vascular Remodeling

BACKGROUND

Earlier, we reported that the simultaneous exposure of pulmonary arterial smooth muscle cells to HIV proteins and cocaine results in the attenuation of antiproliferative bone morphogenetic protein receptor-2 (BMPR2) protein expression without any decrease in its mRNA levels. Therefore, in this study, we aimed to investigate the micro RNA-mediated posttranscriptional regulation of BMPR2 expression.

METHODS AND RESULTS

We identified a network of BMPR2 targeting micro RNAs including miR-216a to be upregulated in response to cocaine and Tat-mediated augmentation of oxidative stress and transforming growth factor-β signaling in human pulmonary arterial smooth muscle cells. By using a loss or gain of function studies, we observed that these upregulated micro RNAs are involved in the Tat- and cocaine-mediated smooth muscle hyperplasia via regulation of BMPR2 protein expression. These in vitro findings were further corroborated using rat pulmonary arterial smooth muscle cells isolated from HIV transgenic rats exposed to cocaine. More importantly, luciferase reporter and in vitro translation assays demonstrated that direct binding of novel miR-216a and miR-301a to 3'UTR of BMPR2 results in the translational repression of BMPR2 without any degradation of its mRNA.

CONCLUSIONS

We identified for the first time miR-216a as a negative modulator of BMPR2 translation and observed it to be involved in HIV protein(s) and cocaine-mediated enhanced proliferation of pulmonary smooth muscle cells.

Drug-induced pulmonary arterial hypertension: a primer for clinicians and scientists

Drug-induced pulmonary arterial hypertension (D-PAH) is a form of World Health Organization Group 1 pulmonary hypertension (PH) defined by severe small vessel loss and obstructive vasculopathy, which leads to progressive right heart failure and death. To date, 16 different compounds have been associated with D-PAH, including anorexigens, recreational stimulants, and more recently, several Food and Drug Administration-approved medications. Although the clinical manifestation, pathology, and hemodynamic profile of D-PAH are indistinguishable from other forms of pulmonary arterial hypertension, its clinical course can be unpredictable and to some degree dependent on removal of the offending agent. Because only a subset of individuals develop D-PAH, it is probable that genetic susceptibilities play a role in the pathogenesis, but the characterization of the genetic factors responsible for these susceptibilities remains rudimentary. Besides aggressive treatment with PH-specific therapies, the major challenge in the management of D-PAH remains the early identification of compounds capable of injuring the pulmonary circulation in susceptible individuals. The implementation of pharmacovigilance, precision medicine strategies, and global warning systems will help facilitate the identification of high-risk drugs and incentivize regulatory strategies to prevent further outbreaks of D-PAH. The goal for this review is to inform clinicians and scientists of the prevalence of D-PAH and to highlight the growing number of common drugs that have been associated with the disease.

Hyperactive TGF-β Signaling in Smooth Muscle Cells Exposed to HIV-protein(s) and Cocaine: Role in Pulmonary Vasculopathy

We earlier demonstrated synergistic increase in the proliferation of pulmonary smooth muscle cells on exposure to HIV-proteins and/or cocaine due to severe down-modulation of bone morphogenetic protein receptor (BMPR) axis: the anti-proliferative arm of TGF-β super family of receptors. Here, now we demonstrate the effect of HIV-Tat and cocaine on the proliferative TGF-β signaling cascade. We observed a significant increase in the secretion of TGF-β1 ligand along with enhanced protein expression of TGFβ Receptor (TGFβR)-1, TGFβR-2 and phosphorylated SMAD2/3 in human pulmonary arterial smooth muscle cells on treatment with cocaine and Tat. Further, we noticed an increase in the levels of p-TAK1 complexed with TGFβR-2. Concomitant to this a significant increase in the activation of TAK1-mediated, SMAD-independent downstream signaling molecules: p-MKK4 and p-JNK was observed. However, activation of MKK3/6-p38MAPK, another axis downstream of TAK1 was found to be reduced due to attenuation in the protein levels of BMPR2. Both SMAD and non-SMAD dependent TGFβR cascades were found to contribute to hyper-proliferation. Finally the increase in the levels of phosphorylated TGFβR1 and TGFβR2 on exposure to HIV-proteins and cocaine was confirmed in pulmonary smooth muscle cells from cocaine injected HIV-transgenic rats and in total lung extracts from HIV infected cocaine and/or opioid users.

Effect of Cocaine on Pulmonary Vascular Remodeling and Hemodynamics in Human Immunodeficiency Virus-Transgenic Rats

Human immunodeficiency virus (HIV)-related pulmonary arterial hypertension has been found to be more prevalent in intravenous drug users. Our earlier cell-culture findings reported down-regulation of bone morphogenetic protein receptors (BMPRs) in combination with enhanced proliferation of human pulmonary arterial smooth muscle cells (PASMCs) in the presence of HIV-Trans-activator of transcription (Tat) and cocaine compared with either treatment alone. Here, we report physiologic evidence of significant increases in mean pulmonary arterial pressure in HIV-transgenic (Tg) rats intraperitoneally administered 40 mg/kg body weight cocaine (HIV-cocaine group) once daily for 21 days when compared with HIV-Tg rats given saline (HIV group) or wild-type (WT) Fischer 334 rats treated with (WT-cocaine group) and without cocaine (WT group). In addition, right ventricle systolic pressure was also found to be significantly higher in the HIV-cocaine rats compared with the WT group. Significant down-regulation in protein expression of BMPR-2 and BMPR-1B was observed in total lung extract from HIV-cocaine rats compared with the other three groups. Furthermore, the PASMCs isolated from HIV-cocaine rats demonstrated a higher level of proliferation and lower levels of apoptosis compared with cells isolated from other rat groups. Interestingly, corroborating our earlier cell-culture findings, we observed higher expression of BMPR-2 and BMPR-1B messenger RNA and significantly lower levels of BMPR-2 and BMPR-1B protein in HIV-cocaine PASMCs compared with cells isolated from all other groups. In conclusion, our findings support an additive effect of cocaine and HIV on smooth muscle dysfunction, resulting in enhanced pulmonary vascular remodeling with associated elevation of mean pulmonary arterial pressure and right ventricle systolic pressure in HIV-Tg rats exposed to cocaine.

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

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 hyper-proliferative 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 (M+T) 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.

Ligand-Independent Activation of Platelet-Derived Growth Factor Receptor β during Human Immunodeficiency Virus-Transactivator of Transcription and Cocaine-Mediated Smooth Muscle Hyperplasia

Our previous study supports an additive effect of cocaine to human immunodeficiency virus infection in the development of pulmonary arteriopathy through enhancement of proliferation of pulmonary smooth muscle cells (SMCs), while also suggesting involvement of platelet-derived growth factor receptor (PDGFR) activation in the absence of further increase in PDGF-BB ligand. Redox-related signaling pathways have been shown to regulate tyrosine kinase receptors independent of ligand binding, so we hypothesized that simultaneous treatment of SMCs with transactivator of transcription (Tat) and cocaine may be able to indirectly activate PDGFR through modulation of reactive oxygen species (ROS) without the need for PDGF binding. We found that blocking the binding of ligand using suramin or monoclonal IMC-3G3 antibody significantly reduced ligand-induced autophosphorylation of Y1009 without affecting ligand-independent transphosphorylation of Y934 residue on PDGFRβ in human pulmonary arterial SMCs treated with both cocaine and Tat. Combined treatment of human pulmonary arterial SMCs with cocaine and Tat resulted in augmented production of superoxide radicals and hydrogen peroxide when compared with either treatment alone. Inhibition of this ROS generation prevented cocaine- and Tat-mediated Src activation and transphosphorylation of PDGFRβ at Y934 without any changes in phosphorylation of Y1009, in addition to attenuation of smooth muscle hyperplasia. Furthermore, pretreatment with an Src inhibitor, PP2, also suppressed cocaine- and Tat-mediated enhanced Y934 phosphorylation and smooth muscle proliferation. Finally, we report total abrogation of cocaine- and Tat-mediated synergistic increase in cell proliferation on inhibition of both ligand-dependent and ROS/Src-mediated ligand-independent phosphorylation of PDGFRβ.

HIV-1/cocaine induced oxidative stress disrupts tight junction protein-1 in human pulmonary microvascular endothelial cells: role of Ras/ERK1/2 pathway

Intravenous drug use (IVDU) is the major risk factor in the development of HIV-related pulmonary arterial hypertension (HRPAH); however, the pathogenesis of HRPAH in association with IVDU has yet to be characterized. Endothelial injury is considered to be an initiating factor for pulmonary vascular remodeling in animal models of PAH. Our previous study shows that simultaneous exposure to HIV-Trans-activator of transcription (Tat) and cocaine exacerbates both disruption of tight junction proteins and permeability of human pulmonary artery endothelial cells compared with either treatment alone. We here now demonstrate that this HIV-Tat and cocaine mediated endothelial dysfunction accompanies with increase in hydrogen peroxide and superoxide radicals generation and involves redox sensitive signaling pathway. Pretreatment with antioxidant cocktail attenuated the cocaine and Tat mediated disassembly of Zonula Occludens (ZO)-1 and enhancement of endothelial monolayer permeability. Furthermore, inhibition of NADPH oxidase by apocynin or siRNA-mediated knockdown of gp-91(phox) abolished the Tat/cocaine-induced reactive oxygen species (ROS) production, suggesting the NADPH oxidase mediated generation of oxidative radicals. In addition, ROS dependent activation of Ras and ERK1/2 Kinase was observed to be mediating the TJP-1 disassembly, and endothelial dysfunction in response to cocaine and Tat exposure. In conclusion, our findings demonstrate that Tat/cocaine -mediated production of ROS activate Ras/Raf/ERK1/2 pathway that contributes to disruption of tight junction protein leading to pulmonary endothelial dysfunction associated with pulmonary vascular remodeling.

Downregulation of bone morphogenetic protein receptor axis during HIV-1 and cocaine-mediated pulmonary smooth muscle hyperplasia: implications for HIV-related pulmonary arterial hypertension

OBJECTIVE

Our previous findings support an additive effect of cocaine to HIV infection in the development of pulmonary arteriopathy through enhanced proliferation of human pulmonary smooth muscle cells. We now examined the role of antiproliferative bone morphogenetic protein receptor (BMPR) axis in HIV protein and cocaine-mediated pulmonary smooth muscle hyperplasia.

APPROACH AND RESULTS

Stimulation of BMPR axis resulted in attenuation of synergistic increase in the proliferation of human pulmonary arterial smooth muscle cells in response to cocaine and HIV protein, transactivator of transcription (Tat). Interestingly, an increase in mRNA but decrease in protein levels of BMPR with correlated decrease in the activation of Sma- and MAD-related family protein 1/5/8 and Id1 gene expression was observed on combined treatment with cocaine and Tat when compared with the untreated cells at all time points tested. Although longer exposure to either cocaine or Tat alone also resulted in a significant decrease in the BMPR protein expression, the abrogation on combined treatment was still significantly more when compared with that of the monotreatments. Significant increase in mRNA but downmodulation of BMPR protein expression was also observed in the lung extracts from HIV-infected intravenous drug users (HIV+IVDU) when compared with that from HIV-infected non-IVDUs (HIV) or uninfected IVDUs (IVDU). Furthermore, significant decrease in BMPR protein expression was also observed in HIV or IVDUs when compared with normal controls that correlated with in vitro findings on chronic exposure to cocaine or HIV protein alone.

CONCLUSIONS

Simultaneous exposure of pulmonary smooth muscle cells to viral protein(s) and cocaine exacerbates downregulation of BMPR axis that may result in enhanced pulmonary vasculature aberrations in HIV+IVDUs.

Enhanced pulmonary arteriopathy in simian immunodeficiency virus-infected macaques exposed to morphine

RATIONALE

HIV-associated pulmonary arterial hypertension (PAH) is likely a more prevalent noninfectious complication of AIDS than previously recognized. Furthermore, the majority of HIV-PAH cases occur in individuals with a history of intravenous drug use. In this study we used a simian immunodeficiency (SIV) macaque model and a primary cell-culture system to investigate the association between drug abuse and HIV infection in HIV-PAH development.

METHODS

The archival lung tissues from macaques previously used to study the effect of morphine on SIV infection-associated neuropathogenesis were analyzed for pulmonary vascular changes. The direct effect of HIV proteins and illicit drugs was investigated on oxidative stress, survival, and proliferation of human pulmonary microvascular endothelial cells.

MEASUREMENTS AND MAIN RESULTS

SIVmacR71/17E-infected rhesus macaques treated with morphine (VM group) demonstrated significant pulmonary vascular remodeling, including the presence of early and advanced complex (plexiform) lesions, when compared with either the SIV-infected (V group) or morphine-treated uninfected (M group) macaques. However, both the V (two of five) and VM (two of six) groups included some animals with Pneumocystis jirovecii pneumonia. The endothelial cells lining the vessels with medial hypertrophy or initial-stage intimal lesions in lung sections from VM macaques demonstrated an increase in positivity for both terminal dUTP nick-end labeling and Ki67. Oxidative stress-mediated enhanced apoptosis followed by enhanced proliferation of endothelial cells was observed on simultaneous treatment with viral proteins and drugs of abuse compared with either treatment alone.

CONCLUSIONS

Our findings suggest that SIV/HIV protein(s) and morphine interact to cause the proliferation of apoptosis-resistant endothelial cells leading to angio-obliteration.

Hypoxia-inducible factor-1 α/platelet derived growth factor axis in HIV-associated pulmonary vascular remodeling

Background

Human immunodeficiency virus (HIV) infected patients are at increased risk for the development of pulmonary arterial hypertension (PAH). Recent reports have demonstrated that HIV associated viral proteins induce reactive oxygen species (ROS) with resultant endothelial cell dysfunction and related vascular injury. In this study, we explored the impact of HIV protein induced oxidative stress on production of hypoxia inducible factor (HIF)-1α and platelet-derived growth factor (PDGF), critical mediators implicated in the pathogenesis of HIV-PAH.

Methods

The lungs from 4-5 months old HIV-1 transgenic (Tg) rats were assessed for the presence of pulmonary vascular remodeling and HIF-1α/PDGF-BB expression in comparison with wild type controls. Human primary pulmonary arterial endothelial cells (HPAEC) were treated with HIV-associated proteins in the presence or absence of pretreatment with antioxidants, for 24 hrs followed by estimation of ROS levels and western blot analysis of HIF-1α or PDGF-BB.

Results

HIV-Tg rats, a model with marked viral protein induced vascular oxidative stress in the absence of active HIV-1 replication demonstrated significant medial thickening of pulmonary vessels and increased right ventricular mass compared to wild-type controls, with increased expression of HIF-1α and PDGF-BB in HIV-Tg rats. The up-regulation of both HIF-1α and PDGF-B chain mRNA in each HIV-Tg rat was directly correlated with an increase in right ventricular/left ventricular+septum ratio. Supporting our in-vivo findings, HPAECs treated with HIV-proteins: Tat and gp120, demonstrated increased ROS and parallel increase of PDGF-BB expression with the maximum induction observed on treatment with R5 type gp-120_CM. Pre-treatment of endothelial cells with antioxidants or transfection of cells with HIF-1α small interfering RNA resulted in abrogation of gp-120_CM mediated induction of PDGF-BB, therefore, confirming that ROS generation and activation of HIF-1α plays critical role in gp120 mediated up-regulation of PDGF-BB.

Conclusion

In summary, these findings indicate that viral protein induced oxidative stress results in HIF-1α dependent up-regulation of PDGF-BB and suggests the possible involvement of this pathway in the development of HIV-PAH.

Morphine enhances Tat-induced activation in murine microglia

There is increasing evidence that opiates accelerate the pathogenesis and progression of acquired immunodeficiency syndrome (AIDS), as well as the incidence of human immunodeficiency virus (HIV) encephalitis (HIVE), a condition characterized by inflammation, leukocyte infiltration, and microglial activation. The mechanisms, by which the HIV-1 transactivating protein Tat and opioids exacerbate microglial activation, however, are not fully understood. In the current study, we explored the effects of morphine and HIV-1 Tat(1-72) on the activation of mouse BV-2 microglial cells and primary mouse microglia. Both morphine and Tat exposure caused up-regulation of the chemokine receptor CCR5, an effect blocked by the opioid receptor antagonist naltrexone. Morphine in combination with Tat also induced morphological changes in the BV-2 microglia from a quiescent to an activated morphology, with a dramatic increase in the expression of the microglial activation marker CD11b, as compared with cells exposed to either agent alone. In addition, the mRNA expression of inducible nitric oxide synthase (iNOS), CD40 ligand, Interferon-gamma-inducible protein 10 (IP-10), and the proinflammatory cytokines tumor necrosis factor alpha (TNFalpha), interleukin (IL)-1beta, and IL-6, which were elevated with Tat alone, were dramatically enhanced with Tat in the presence of morphine. In summary, these findings shed light on the cooperative effects of morphine and HIV-1 Tat on both microglial activation and HIV coreceptor up-regulation, effects that could result in exacerbated neuropathogenesis.

Effect of cocaine on human immunodeficiency virus-mediated pulmonary endothelial and smooth muscle dysfunction

Human immunodeficiency virus (HIV)-associated pulmonary arterial hypertension (PAH) is a devastating, noninfectious complication of acquired immune deficiency syndrome, and the majority of HIV-PAH cases occur in individuals with a history of intravenous drug use (IVDU). However, although HIV-1 and IVDU have been associated with PAH independently or in combination, the pathogenesis of the disproportionate presence of HIV-PAH in association with IVDU has yet to be characterized. The objective of this study was to obtain a better understanding of the interactions between HIV-1 and cocaine to help uncover the mechanism(s) of the development of HIV-PAH. We observed that exposure of HIV-infected macrophages or HIV-Trans-Activator of Transcription (Tat)-treated pulmonary endothelial cells to cocaine enhanced the expression of platelet-derived growth factor (PDGF)-BB. Simultaneous treatment with Tat and cocaine, on the other hand, exacerbated both the disruption of tight junction proteins (TJPs), with enhanced permeability in pulmonary endothelial cells, and the proliferation of pulmonary smooth muscle cells (pSMCs) compared with either treatment alone. Histological examination of HIV plus IVDU human lung sections showed signs of early pulmonary arteriopathy, severe down-modulation of TJPs, and increased expression of PDGF-BB compared with the lung sections from individuals who are infected with HIV and without history of IVDU. Interestingly, blocking of PDGF receptor signaling with the receptor antagonist or small interfering RNA has been shown to inhibit the increase in proliferation of pSMCs on Tat and cocaine exposure. Our results, therefore, support an additive effect of cocaine to HIV infection in the development of pulmonary arteriopathy through enhancement of endothelial dysfunction and proliferation of pSMCs, while also suggesting PDGF-PDGF receptor axis as a potential target for use in clinical intervention.

Proinflammatory cytokines and HIV-1 synergistically enhance CXCL10 expression in human astrocytes

HIV encephalitis (HIVE), the pathologic correlate of HIV-associated dementia (HAD) is characterized by astrogliosis, cytokine/chemokine dysregulation, and neuronal degeneration. Increasing evidence suggests that inflammation is actively involved in the pathogenesis of HAD. In fact, the severity of HAD/HIVE correlates more closely with the presence of activated glial cells than with the presence and amount of HIV-infected cells in the brain. Astrocytes, the most numerous cell type within the brain, provide an important reservoir for the generation of inflammatory mediators, including interferon-gamma inducible peptide-10 (CXCL10), a neurotoxin and a chemoattractant, implicated in the pathophysiology of HAD. Additionally, the proinflammatory cytokines, IFN-gamma and TNF-alpha, are also markedly increased in CNS tissues during HIV-1 infection. In this study, we hypothesized that the interplay of host cytokines and HIV-1 could lead to enhanced expression of the toxic chemokine, CXCL10. Our findings demonstrate a synergistic induction of CXCL10 mRNA and protein in human astrocytes exposed to HIV-1 and the proinflammatory cytokines. Signaling molecules, including JAK, STATs, MAPK (via activation of Erk1/2, AKT, and p38), and NF-kappaB were identified as instrumental in the synergistic induction of CXCL10. Understanding the mechanisms involved in HIV-1 and cytokine-mediated up-regulation of CXCL10 could aid in the development of therapeutic modalities for HAD.

HIV-1 Tat co-operates with IFN-gamma and TNF-alpha to increase CXCL10 in human astrocytes

HIV-associated neurological disorders (HAND) are estimated to affect 60% of the HIV infected population. HIV-encephalitis (HIVE), the pathological correlate of the most severe form of HAND is often characterized by glial activation, cytokine/chemokine dysregulation, and neuronal damage and loss. However, the severity of HIVE correlates better with glial activation rather than viral load. One of the characteristic features of HIVE is the increased amount of the neurotoxic chemokine, CXCL10. This chemokine can be released from astroglia activated with the pro-inflammatory cytokines IFN-γ and TNF-α, in conjunction with HIV-1 Tat, all of which are elevated in HIVE. In an effort to understand the pathogenesis of HAND, this study was aimed at exploring the regulation of CXCL10 by cellular and viral factors during astrocyte activation. Specifically, the data herein demonstrate that the combined actions of HIV-1 Tat and the pro-inflammatory cytokines, IFN-γ and TNF-α, result in the induction of CXCL10 at both the RNA and protein level. Furthermore, CXCL10 induction was found to be regulated transcriptionally by the activation of the p38, Jnk, and Akt signaling pathways and their downstream transcription factors, NF-κB and STAT-1α. Since CXCL10 levels are linked to disease severity, understanding its regulation could aid in the development of therapeutic intervention strategies for HAND.

Down modulation of IFN-gamma signaling in alveolar macrophages isolated from smokers

The master cytokine, IFN-gamma possesses a wide spectrum of biological effects and is crucial for development of the highly activated macrophage phenotype characteristically found during inflammation. However, no data exists regarding the potential influence of cigarette smoke on the status of the expression of the cell surface receptor for IFN-gamma (IFN-gammaR) on alveolar macrophages (AM) of smokers. Here in, we report reduction in the expression of the IFN-gammaR alpha-chain on AM of cigarette smokers, when compared with non-smokers. Ensuing from the loss of receptor expression on the AM of smokers there was a decrease in IFN-gamma-mediated cell signaling. This included a decrease in the phosphorylation of signal transducer and activator of transcription (STAT)-1 and induction of interferon regulatory factor (IRF)-1. Further, diminished activation/induction of transcription factors did not appear to result from induction of known members of the 'suppressors of cytokine signaling (SOCS)' family. Decreased IFN-gamma signal transduction in AM from smokers may have an important implication regarding the use of therapeutic IFN-gamma in the lungs of patients that develop respiratory disorders as a result of tobacco use.

Mechanisms of platelet-derived growth factor-mediated neuroprotection--implications in HIV dementia

Platelet-derived growth factor (PDGF) has been implicated in promoting survival and proliferation of immature neurons, and even protecting neurons from gp120-induced cytotoxicity. However, the mechanisms involved in neuroprotection are not well understood. In the present study we demonstrate the role of phosphatidylinositol 3-kinase (PI3K)/Akt signaling in PDGF-mediated neuroprotection. Pharmacological inhibition of PI3K greatly reduced the ability of PDGF-BB to block gp120 IIIB-mediated apoptosis and cell death in human neuroblastoma cells. The role of Akt in PDGF-mediated protection was further corroborated using a dominant-negative mutant of Akt, which was able to block the protective effect of PDGF. We next sequentially examined the signals downstream of Akt in PDGF-mediated protection in human neuroblastoma cells. In cells pretreated with PDGF prior to gp120 there was increased phosphorylation of both GSK-3beta and Bad, an effect that was inhibited by PI3-kinase inhibitor. Nuclear translocation of NF-kappaB, which lies downstream of GSK-3beta, however, remained unaffected in cells treated with PDGF. In addition to inducing phosphorylation of Bad, PDGF-mediated protection also involved down-regulation of the proapoptotic protein Bax. Furthermore, PDGF-mediated protection also involved the inhibition of gp120-induced release of mitochondrial cytochrome C. Our findings thus underscore the roles of both PI3K/Akt and Bcl family pathways in PDGF-mediated neuroprotection.

Cocaine-mediated enhancement of virus replication in macrophages: implications for human immunodeficiency virus-associated dementia

Injection drug use has been recognized as a major risk factor for acquired immunodeficiency syndrome (AIDS) from the outset of the epidemic. Cocaine, one of the most widely abused drugs in the United States, can both impair the functions of macrophages and CD4(+) lymphocytes and also activate human immunodeficiency virus (HIV)-1 expression in these cells. Because the brain is the target organ for both cocaine and HIV, the objective of the present study was to explore the effects of cocaine on virus replication in macrophages, the target cells for the virus in the central nervous system (CNS). Cocaine markedly enhanced virus production in simian human immunodeficiency virus (SHIV)-infected monocyte-derived macrophages (MDMs) and in U1 cells, a chronically infected promonocytic cell line as monitored by enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry. Cocaine treatment also resulted in the activation of nuclear factor (NF)-kappa B and transcriptional activation of the HIV-LTR (long terminal repeat) gag-GFP (green fluorescent protein). Analyses of chemokines in cocaine-treated macrophages by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and Luminex assays suggested increased expression of interleukin (IL)-10, a cytokine that is known to promote HIV replication in MDMs. In addition to enhancing IL-10 expression, cocaine also caused an up-regulation of the macrophage activation marker, human leukocyte antigen (HLA)-DR, in MDMs. The synergistic effect of cocaine on virus replication and its enhancement of host activation markers suggest that cocaine functions at multiple pathways to accelerate HIV-associated dementia (HAD).

Upregulation of expression of platelet-derived growth factor and its receptor in pneumonia associated with SHIV-infected macaques

BACKGROUND

HIV-associated pulmonary disorders are the most frequent cause of AIDS-related deaths. Rhesus macaques infected with SIV-HIV (SHIV) recapitulate the human HIV-1 lung disease and provide an excellent working model to study the pathogenesis of the human syndrome. Lungs of macaques with SHIV-associated pneumonia have pathology involving macrophage and T cell infiltration that is often accompanied with concurrent opportunistic infections.

OBJECTIVE

To explore the relationship between SHIV-associated respiratory disease and the expression of platelet-derived growth factor (PDGF) B chain (PDGF-B) and its cognate receptors, PDGF-Ralpha and PDGF-Rbeta, which have been implicated in chronic inflammatory processes.

METHODS

Lung tissues from 10 SHIV-infected rhesus macaques were evaluated for pathological changes and correlation of these lesions with PDGF-B/PDGF-R expression by real-time reverse transcriptase polymerase chain reaction and immunohistochemistry.

RESULTS

Virus-associated pneumonia was associated with virus replication in macrophages in the lungs, enhanced recruitment of macrophages and mononuclear cells into the organ, and, occasionally, fibrosis. These changes were accompanied by upregulation of PDGF-B and its cognate receptors in the diseased tissue. Confocal microscopy identified SHIV-infected macrophages as one of the major cell types expressing PDGF-B and PDGF-Ralpha/beta in the affected lungs.

CONCLUSION

These results suggest that PDGF and its cognate receptors play a critical role in the pathogenesis of pulmonary disease associated with this virus.

RACK1 inhibits colonic cell growth by regulating Src activity at cell cycle checkpoints

Previously, we showed that Src tyrosine kinases are activated early in the development of human colon cancer and are suppressed as intestinal cells differentiate. We identified RACK1 as an endogenous substrate, binding partner and inhibitor of Src. Here we show (by overexpressing RACK1, depleting Src or RACK1 and utilizing cell-permeable peptides that perturb RACK1's interaction with Src) that RACK1 regulates growth of colon cells by suppressing Src activity at G(1) and mitotic checkpoints, and consequently delaying cell cycle progression. Activated Src rescues RACK1-inhibited growth of HT-29 cells. Conversely, inhibiting Src abolishes growth promoted by RACK1 depletion in normal cells. Two potential mechanisms whereby RACK1 regulates mitotic exit are identified: suppression of Src-mediated Sam68 phosphorylation and maintenance of the cyclin-dependent kinase (CDK) 1-cyclin B complex in an active state. Our results reveal novel mechanisms of cell cycle control in G(1) and mitosis of colon cells. The significance of this work lies in the discovery of a mechanism by which the growth of colon cancer cells can be slowed, by RACK1 suppression of an oncogenic kinase at critical cell cycle checkpoints. Small molecules that mimic RACK1 function may provide a powerful new approach to the treatment of colon cancer.

Therapy of "SHIV" infected macaques with liposomes delivering antisense interleukin-4 DNA

BACKGROUND/OBJECTIVES

To explore the effects of antisense (AS) interleukin (IL)-4 on virus replication and CD8+ T-cell responses in lymph nodes and blood of macaques infected with simian human immunodeficiency virus, SHIV(89.6)P.

METHODS

Six macaques were inoculated with simian human immunodeficiency virus (SHIV(89.6)P). Seven days later, four of the animals were given 1 mg AS IL-4 plasmid complexed with Megafectin liposome, intravenously, and two of these received a second injection of the same material on day 9. All six macaques were killed at 2 weeks post infection (pi) and monitored for viral RNA and CD8+ T cells in blood and lymph nodes by real-time reverse transcriptase-polymerase chain reaction, flow cytometry and immunohistochemistry.

RESULTS

In contrast to the lymph nodes from virus control animals, the lymph nodes of AS IL-4-treated animals had a significant reduction in viral loads and reduced depletion of cells from the nodes. There was an increase in CD8+ T cells in the nodes, and many of the cells expressed granzyme B, suggesting functional activation. This trend of virus reduction and increased CD8+ T cell numbers was also reflected in blood.

CONCLUSIONS

The therapeutic effect of the AS IL-4 suggests indirectly that the acute immunosuppressive disease caused by SHIVs is mediated, in part, by IL-4 that causes enhanced virus replication by suppressing anti-viral CD8+ T-cell responses, and that this effect was reduced by treatment of the animals with AS IL-4.

CXCL10-induced cell death in neurons: role of calcium dysregulation

Chemokines play a key role in the regulation of central nervous system disease. CXCL10 over-expression has been observed in several neurodegenerative diseases, including multiple sclerosis, Alzheimer's disease and HIV-associated dementia. More recent studies by others and us have shown that CXCL10 elicits apoptosis in fetal neurons. The mechanism of CXCL10-mediated neurotoxicity, however, remains unclear. In this study, we provide evidence for the direct role of Ca(2+) dysregulation in CXCL10-mediated apoptosis. We demonstrate that treatment of fetal neuronal cultures with exogenous CXCL10 produced elevations in intracellular Ca(2+) and that this effect was modulated via the binding of CXCL10 to its cognate receptor, CXCR3. We further explored the association of intracellular Ca(2+) elevations with the caspases that are involved in CXC10-induced neuronal apoptosis. Our data showed that increased Ca(2+), which is available for uptake by the mitochondria, is associated with membrane permeabilization and cytochrome c release from this compartment. The released cytochrome c then activates the initiator active caspase-9. This initiator caspase sequentially activates the effector caspase-3, ultimately leading to apoptosis. This study identifies the temporal signaling cascade involved in CXCL10-mediated neuronal apoptosis and provides putative targets for pharmaceutical intervention of neurological disorders associated with CXCL10 up-regulation.

Signaling through protein kinases and transcriptional regulators in Candida albicans

The human fungal pathogen Candida albicans switches from a budding yeast form to a polarized hyphal form in response to various external signals. This morphogenetic switching has been implicated in the development of pathogenicity. Several signaling pathways that regulate morphogenesis have been identified, including various transcription factors that either activate or repress hypha-specific genes. Two well-characterized pathways include the MAP kinase cascade and cAMP-dependent protein kinase pathway that regulate the transcription factors Cph1p and Efg1p, respectively. cAMP also appears to interplay with other second messengers: Ca2+, inositol tri-phosphates in regulating yeast-hyphal transition. Other, less-characterized pathways include two component histidine kinases, cyclin-dependent kinase pathway, and condition specific pathways such as pH and embedded growth conditions. Nrg1 and Rfg1 function as transcriptional repressors of hyphal genes via recruitment of Tup1 co-repressor complex. Different upstream signals converge into a common downstream output during hyphal switch. The levels of expression of several genes have been shown to be associated with hyphal morphogenesis rather than with a specific hypha-inducing condition. Hyphal development is also linked to the expression of a range of other virulence factors. This review explains the relative contribution of multiple pathways that could be used by Candida albican cells to sense subtle differences in the growth conditions of its native host environment.

Influence of W-7, a calmodulin antagonist on phospholipid biosynthesis in Candida albicans

AIM

This study was undertaken to investigate the role of calmodulin in phospholipid biosynthesis in Candida albicans using W-7, a calmodulin antagonist.

METHODS

Cells were grown as shake cultures in the absence and presence of W-7 at different concentrations. Changes in cell mass, phospholipid content and incorporation of labelled precursor into phospholipid and activities of respective enzymes have been studied.

RESULTS

Decreased incorporation of labelled acetate into total lipids and phospholipids was observed in the presence of 40 microm of W-7 which was not as a consequence of altered growth of Candida in the presence of calmodulin antagonist. Further, a significant decrease in the levels of calmodulin and CaM dependent protein kinase activity was observed in cells grown with different concentrations of W-7. This was accompanied by decreased/increased activity of phosphatidic acid phosphatase and phospholipase A, respectively in W-7 grown cells as compared to controls.

CONCLUSIONS

These findings suggest definite involvement of calmodulin in the regulation of phospholipid metabolism in Candida albicans.

Cyclin E overexpression enhances cytokine-mediated apoptosis in MCF7 breast cancer cells

Cyclin E, the regulatory component of the cyclin E/cyclin-dependent kinase (CDK) complex, is required for proliferation and overexpression of this cyclin is associated with many types of human tumors. To elucidate the mechanism by which cyclin E overexpression promotes tumorigenesis, cyclin E was overexpressed in two breast cancer lines: MCF7 and T47D. Cells overexpressing cyclin E display a marked decrease in the expression of Bcl-2, an antiapoptotic protein, and increased levels of the proapoptotic proteins Bad and Bax. The levels of Bcl-X(L) and Mcl-1 remain unchanged. Since the homeostasis of pro- and antiapoptotic proteins was altered, we asked if cyclin E overexpression modifies responses to cytokines. MCF7 cyclin E overexpressing cells have an enhanced sensitivity to Fas, TRAIL, and TNF-alpha-induced apoptosis. T47D cells overexpressing cyclin E have a significant increase in TNF-alpha and TRAIL-induced apoptosis. In conclusion, our results provide a link between expression of cyclin E, deregulation of Bcl-2, and an altered response to cytokine-mediated apoptosis.