HIV-1 TAT represses transcription of the bone morphogenic protein receptor-2 in U937 monocytic cells

Bone Tissue Changes in Individuals Living with HIV/AIDS: The Importance of a Hierarchical Approach in Investigating Bone Fragility

Skeletal alterations and their complications can significantly impact the quality of life and overall prognosis of patients living with HIV (PLWHIV). Considering skeletal alterations are often asymptomatic and unapparent during routine clinical evaluation, these conditions are frequently overlooked in the clinical management of PLWHIV. However, since the use of combined antiretroviral therapy (cART) has increased life expectancy in PLWHIV effectively, osteopenia, osteoporosis, and bone fragility are now considered to have a major health impact, with a substantial increase in healthcare costs. This narrative literature review aimed to provide a comprehensive overview of the contemporary literature related to bone changes in PLWHIV, focusing on the importance of taking a multi-scale approach in the assessment of bone hierarchical organization. Even though a low bone mineral density is frequently reported in PLWHIV, numerous ambiguities still remain to be solved. Recent data suggest that assessment of other bone properties (on various levels of the bone structure) could contribute to our understanding of bone fragility determinants in these individuals. Special attention is needed for women living with HIV/AIDS since a postmenopausal status was described as an important factor that contributes to skeletal alterations in this population. Further research on complex etiopathogenetic mechanisms underlying bone alterations in PLWHIV may lead to the development of new therapeutic approaches specifically designed to reduce the health burden associated with skeletal disorders in this population. A major challenge in the clinical management of PLWHIV lies in the adverse skeletal effects of some frequently prescribed cART regimens (e.g., regimens containing tenofovir disoproxil fumarate), which may require a switch to other pharmacological approaches for maintained HIV infection (e.g., regimens containing tenofovir alafenamide). Taken together, the findings are indicative that the HIV/AIDS status should be taken into consideration when designing new guidelines and strategies for individualized prevention, diagnosis, and treatment of increased bone fragility.

The Intersection of HIV and Pulmonary Vascular Health: From HIV Evolution to Vascular Cell Types to Disease Mechanisms

People living with HIV (PLWH) face a growing burden of chronic diseases, owing to the combinations of aging, environmental triggers, lifestyle choices, and virus-induced chronic inflammation. The rising incidence of pulmonary vascular diseases represents a major concern for PLWH. The study of HIV-associated pulmonary vascular complications ideally requires a strong understanding of pulmonary vascular cell biology and HIV pathogenesis at the molecular level for effective applications in infectious diseases and vascular medicine. Active HIV infection and/or HIV proteins disturb the delicate balance between vascular tone and constriction, which is pivotal for maintaining pulmonary vascular health. One of the defining features of HIV is its high genetic diversity owing to several factors including its high mutation rate, recombination between viral strains, immune selective pressures, or even geographical factors. The intrinsic HIV genetic diversity has several important implications for pathogenic outcomes of infection and the overall battle to combat HIV. Challenges in the field present themselves from two sides of the same coin: those imposed by the virus itself and those stemming from the host. The field may be advanced by further developing in vivo and in vitro models that are well described for both pulmonary vascular diseases and HIV for mechanistic studies. In essence, the study of HIV-associated pulmonary vascular complications requires a multidisciplinary approach, drawing upon insights from both infectious diseases and vascular medicine. In this review article, we discuss the fundamentals of HIV virology and their impact on pulmonary disease, aiming to enhance the understanding of either area or both simultaneously. Bridging the gap between preclinical research findings and clinical practice is essential for improving patient care. Addressing these knowledge gaps requires interdisciplinary collaborations, innovative research approaches, and dedicated efforts to prioritize HIV-related pulmonary complications on the global research agenda.

Human Endogenous Retrovirus, SARS-CoV-2, and HIV Promote PAH via Inflammation and Growth Stimulation

Pulmonary arterial hypertension (PAH) is a pulmonary vascular disease characterized by the progressive elevation of pulmonary arterial pressures. It is becoming increasingly apparent that inflammation contributes to the pathogenesis and progression of PAH. Several viruses are known to cause PAH, such as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), human endogenous retrovirus K(HERV-K), and human immunodeficiency virus (HIV), in part due to acute and chronic inflammation. In this review, we discuss the connections between HERV-K, HIV, SARS-CoV-2, and PAH, to stimulate research regarding new therapeutic options and provide new targets for the treatment of the disease.

Pulmonary Arterial Hypertension in Patients Infected with the Human Immunodeficiency Virus

It is important to recognize and treat human immunodeficiency virus-associated pulmonary arterial hypertension (HIV-PAH) because of the associated morbidity and mortality. With the introduction of antiretroviral therapies (ART), improved survival has changed the focus of treatment management from immunodeficiency-related opportunistic infections to chronic cardiovascular complications, including HIV-PAH. The 2018 6th World Symposium of Pulmonary Hypertension recommended a revised definition of PAH that might result in a greater number of patients with HIV-PAH; however, the implication of this change is not yet clear. Here, we review the current literature on the diagnosis, management, and outcomes of patients with HIV-PAH.

Exercise-induced pulmonary hypertension in HIV patients: Association with poor clinical and immunological status

BACKGROUND AND AIM

Exercise-induced pulmonary hypertension (Ex-PH) may represent the earliest sign of pulmonary arterial hypertension (PAH) in human immunodeficiency virus (HIV) patients. We investigated its association with clinical and immunological status, virologic control, and response to antiviral therapy.

METHODS

In 32 consecutive HIV patients with either low (n = 29) or intermediate probability (n = 3) of PH at rest, we evaluated the association of isolated ExPH with: time to HIV diagnosis; CD4+ T-cell count; clinical progression to acquired immunodeficiency syndrome (AIDS); development of resistance to antiretroviral therapy (ART); HIV RNA levels; time to beginning of ART; current use of protease inhibitors; combination of ART with boosters (ritonavir or cobicistat); immuno-virologic response to ART; and ART discontinuation. Isolated ExPH at stress echocardiography (ESE) was defined as absence of PH at rest and systolic pulmonary arterial pressure (sPAP) >45 mmHg or a >20 mmHg increase during low-intensity exercise cardiac output (<10 L/min).

RESULTS

In our cohort, 22% (n = 7) of the enrolled population developed ExPH which was inversely related to CD4+ T-cell count (p = 0.047), time to HIV diagnosis (p = 0.014) and time to onset of ART (p = 0.041). Patients with ExPH had a worse functional class than patients without ExPH (p < 0.001). ExPH and AIDS showed a trend (p = 0.093) to a direct relationship. AIDS patients had a higher pulmonary vascular resistance compared to patients without ExPH (p = 0.020) at rest echocardiography.

CONCLUSIONS

The presence of isolated ExPH associates with a worse clinical status and poor immunological control in HIV patients. Assessment of ExPH by ESE may help identify subgroups of HIV patients with a propensity to develop subclinical impairment of pulmonary circulation following poor control of HIV infection.

Influence of HIV Infection and Antiretroviral Therapy on Bone Homeostasis

The human immunodeficiency virus type 1 (HIV)/AIDS pandemic represents the most significant global health challenge in modern history. This infection leads toward an inflammatory state associated with chronic immune dysregulation activation that tilts the immune-skeletal interface and its deep integration between cell types and cytokines with a strong influence on skeletal renewal and exacerbated bone loss. Hence, reduced bone mineral density is a complication among HIV-infected individuals that may progress to osteoporosis, thus increasing their prevalence of fractures. Highly active antiretroviral therapy (HAART) can effectively control HIV replication but the regimens, that include tenofovir disoproxil fumarate (TDF), may accelerate bone mass density loss. Molecular mechanisms of HIV-associated bone disease include the OPG/RANKL/RANK system dysregulation. Thereby, osteoclastogenesis and osteolytic activity are promoted after the osteoclast precursor infection, accompanied by a deleterious effect on osteoblast and its precursor cells, with exacerbated senescence of mesenchymal stem cells (MSCs). This review summarizes recent basic research data on HIV pathogenesis and its relation to bone quality. It also sheds light on HAART-related detrimental effects on bone metabolism, providing a better understanding of the molecular mechanisms involved in bone dysfunction and damage as well as how the HIV-associated imbalance on the gut microbiome may contribute to bone disease.

Pulmonary Hypertension in HIV

Human immunodeficiency virus-associated pulmonary arterial hypertension (HIV-PAH) is important to recognize given its association with significant morbidity and mortality. With the introduction of antiretroviral therapy, the focus of disease management has largely shifted from treating immunodeficiency-related opportunistic infections to managing chronic cardiopulmonary complications. Symptoms are nonspecific, and a high index of clinical suspicion is needed to avoid significant delay in the diagnosis of HIV-PAH. Although several viral proteins have been implicated in the pathogenesis of HIV-PAH, the exact mechanism remains uncertain. Further studies are needed to elucidate precise pathogenic mechanisms, early diagnostic tools, and novel therapeutic targets to improve prognosis of this severe complication.

Pulmonary hypertension in patients with a history of intravenous drug use

OBJECTIVE

Pulmonary hypertension may be a consequence of intrinsic elevation in pulmonary vasculature resistance or complicate numerous other conditions affecting the cardiac and respiratory systems. In this review we sought to explore the relationship between pulmonary hypertension and intravenous drug use.

METHODS

A narrative review was conducted using PubMed MeSH search with further papers identified using a standard PubMed search with relevant key terms and various synonyms.

RESULTS

HIV infection may be associated with pulmonary hypertension due to indirect consequences of viral infection, venous thromboembolism or its therapies. Anti-retroviral infection may also influence plasma concentrations of commonly used treatments for pulmonary hypertension. Intravenous drug use is acknowledged as an important portal for the acquisition of hepatitis virus C infection, with portopulmonary hypertension a potential complication associated with poor prognosis. Interferon based therapy, used in treatment of chronic hepatitis C infection, may also play a causal role in the development of pulmonary hypertension. More recently, sofosbuvir has been linked to development or exacerbation of pulmonary arterial hypertension. Certain drugs of abuse may cause pulmonary hypertension due to properties that result in direct injury to the pulmonary vasculature. The potential for embolic phenomena, complicating venous thromboembolism, recurrent embolization of particulate matter or because of right-sided endocarditis, resulting in pulmonary hypertension is an important contributing factor in the pathophysiology in this unique cohort.

CONCLUSIONS

Eliciting a history of intravenous drug use is important and may be associated with a number of less common etiologies, each with specific diagnostic and therapeutic implications.

Antiviral activity of bone morphogenetic proteins and activins

Understanding the control of viral infections is of broad importance. Chronic hepatitis C virus (HCV) infection causes decreased expression of the iron hormone hepcidin, which is regulated by hepatic bone morphogenetic protein (BMP)/SMAD signalling. We found that HCV infection and the BMP/SMAD pathway are mutually antagonistic. HCV blunted induction of hepcidin expression by BMP6, probably via tumour necrosis factor (TNF)-mediated downregulation of the BMP co-receptor haemojuvelin. In HCV-infected patients, disruption of the BMP6/hepcidin axis and genetic variation associated with the BMP/SMAD pathway predicted the outcome of infection, suggesting that BMP/SMAD activity influences antiviral immunity. Correspondingly, BMP6 regulated a gene repertoire reminiscent of type I interferon (IFN) signalling, including upregulating interferon regulatory factors (IRFs) and downregulating an inhibitor of IFN signalling, USP18. Moreover, in BMP-stimulated cells, SMAD1 occupied loci across the genome, similar to those bound by IRF1 in IFN-stimulated cells. Functionally, BMP6 enhanced the transcriptional and antiviral response to IFN, but BMP6 and related activin proteins also potently blocked HCV replication independently of IFN. Furthermore, BMP6 and activin A suppressed growth of HBV in cell culture, and activin A inhibited Zika virus replication alone and in combination with IFN. The data establish an unappreciated important role for BMPs and activins in cellular antiviral immunity, which acts independently of, and modulates, IFN.

HIV transgene expression impairs K+ channel function in the pulmonary vasculature

Human immunodeficiency virus (HIV) infection is an established risk factor for pulmonary arterial hypertension (PAH); however, the pathogenesis of HIV-related PAH remains unclear. Since K⁺ channel dysfunction is a common marker in most forms of PAH, our aim was to analyze whether the expression of HIV proteins is associated with impairment of K⁺ channel function in the pulmonary vascular bed. HIV transgenic mice (Tg26) expressing seven of the nine HIV viral proteins and wild-type (WT) mice were used. Hemodynamic assessment was performed by echocardiography and catheterization. Vascular reactivity was studied in endothelium-intact pulmonary arteries. K⁺ currents were recorded in freshly isolated pulmonary artery smooth muscle cells (PASMC) using the patch-clamp technique. Gene expression was assessed using quantitative RT-PCR. PASMC from Tg26 mice had reduced K⁺ currents and were more depolarized than those from WT. Whereas voltage-gated K⁺ channel 1.5 (Kv1.5) currents were preserved, pH-sensitive noninactivating background currents ( I_KN) were nearly abolished in PASMC from Tg26 mice. Tg26 mice had reduced lung expression of Kv7.1 and Kv7.4 channels and decreased responses to the Kv7.1 channel activator L-364,373 assessed by vascular reactivity and patch-clamp experimental approaches. Although we found pulmonary vascular remodeling and endothelial dysfunction in Tg26 mice, this was not accompanied by changes in hemodynamic parameters. In conclusion, the expression of HIV proteins in vivo impairs pH-sensitive I_KN and Kv7 currents. This negative impact of HIV proteins in K⁺ channels was not sufficient to induce PAH, at least in mice, but may play a permissive or accessory role in the pathophysiology of HIV-associated PAH.

HIV-associated pulmonary hypertension

PURPOSE OF REVIEW

HIV-associated pulmonary arterial hypertension (HIV-PAH) is a well-recognized severe cardiovascular complication of HIV infection that confers an adverse prognosis irrespective of the stage of disease. This review will summarize the available data on HIV-PAH epidemiology and provide insights into the pathophysiology and therapeutic strategies currently available.

RECENT FINDINGS

Patients with HIV are several thousand times more likely to develop HIV-PAH compared to the incidence of idiopathic PAH. Several HIV viral proteins are implicated in the pathogenesis although the exact mechanism remains unknown. In the past two decades, there have been several new treatment strategies that appear effective in treating HIV-PAH. Novel pathophysiologic mechanisms implicating the transforming growth factor β receptor family may offer novel therapeutic targets in the future.

SUMMARY

As antiretroviral therapy continues to improve health outcomes for patients with HIV, there needs to be a shift in focus of care toward chronic noncommunicable diseases. Among cardiovascular disease-complicating chronic HIV infection, HIV-PAH is a severe progressive disease that leads to right heart failure and death. Currently available treatment strategies are effective, however, furthering our understanding of HIV-PAH will be critical as it is likely to become the commonest cause of PAH worldwide.

HIV-Tat regulates macrophage gene expression in the context of neuroAIDS

Despite the success of cART, greater than 50% of HIV infected people develop cognitive and motor deficits termed HIV-associated neurocognitive disorders (HAND). Macrophages are the major cell type infected in the CNS. Unlike for T cells, the virus does not kill macrophages and these long-lived cells may become HIV reservoirs in the brain. They produce cytokines/chemokines and viral proteins that promote inflammation and neuronal damage, playing a key role in HIV neuropathogenesis. HIV Tat is the transactivator of transcription that is essential for replication and transcriptional regulation of the virus and is the first protein to be produced after HIV infection. Even with successful cART, Tat is produced by infected cells. In this study we examined the role of the HIV Tat protein in the regulation of gene expression in human macrophages. Using THP-1 cells, a human monocyte/macrophage cell line, and their infection with lentivirus, we generated stable cell lines that express Tat-Flag. We performed ChIP-seq analysis of these cells and found 66 association sites of Tat in promoter or coding regions. Among these are C5, CRLF2/TSLPR, BDNF, and APBA1/Mint1, genes associated with inflammation/damage. We confirmed the association of Tat with these sequences by ChIP assay and expression of these genes in our THP-1 cell lines by qRT-PCR. We found that HIV Tat increased expression of C5, APBA1, and BDNF, and decreased CRLF2. The K50A Tat-mutation dysregulated expression of these genes without affecting the binding of the Tat complex to their gene sequences. Our data suggest that HIV Tat, produced by macrophage HIV reservoirs in the brain despite successful cART, contributes to neuropathogenesis in HIV-infected people.

Quantitative proteomic analysis of HIV-1 Tat-induced dysregulation in SH-SY5Y neuroblastoma cells

Despite affecting up to 70% of HIV-positive patients and being the leading cause of dementia in patients under 40 years, the molecular mechanisms involved in the onset of HIV-associated neurocognitive disorders (HAND) are not well understood. To address this, we performed SILAC-based quantitative proteomic analysis on HIV-Tat treated SH-SY5Y neuroblastoma cells. Isolated protein was fractionated by SDS-PAGE and analyzed by nLC-MS/MS on an Orbitrap Velos. Using MaxQuant, we identified and quantified 3077 unique protein groups, of which 407 were differentially regulated. After applying an additional standard deviation-based cutoff, 29 of these were identified as highly significantly and stably dysregulated. GO term analysis shows dysregulation in both protein translation machinery as well as cytoskeletal regulation that have both been implicated in other dementias. In addition, several key cytoskeletal regulatory proteins such as ARHGEF17, the Rho GTPase, SHROOM3, and CMRP1 are downregulated. Together, these data demonstrate that HIV-Tat can dysregulate neuronal cytoskeletal regulatory proteins that could lead to the major HAND clinical manifestation-synapse loss.

Maintaining lung health with longstanding HIV

PURPOSE OF REVIEW

Human immunodeficiency virus (HIV) is now managed as a chronic disease. Non-infectious pulmonary conditions have replaced infection as the biggest threat to lung health, particularly as HIV cohorts age, but there is no consensus on how best to maintain long-term lung health. We review the epidemiology and pathogenesis of chronic obstructive pulmonary disease (COPD), pulmonary arterial hypertension (PAH), and lung cancer in HIV-seropositive individuals.

RECENT FINDINGS

Diagnoses of COPD are now up to 50% more prevalent in HIV-seropositive individuals than HIV-uninfected controls, and prospective pulmonary function studies find significant impairment in 7% to more than 50% of HIV-seropositive individuals. The prevalence of HIV-PAH is 0.2-0.5%, and lung cancer is two to three times more prevalent in HIV-seropositive individuals. Although host factors such as age and smoking have a role, HIV is an independent contributor to the pathogenesis of COPD, PAH, and lung cancer. Chronic inflammation, immune senescence, oxidative stress, and direct effects of viral proteins are all potential pathogenetic mechanisms. Despite their prevalence, non-infectious lung diseases remain underrecognized and evidence for effective screening strategies in HIV-seropositive individuals is limited.

SUMMARY

COPD, PAH, and lung cancer are a growing threat to lung health in the highly active antiretroviral therapy era necessitating early recognition.

Pharmacological treatment of HIV-associated pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a rare but severe disease that results from chronic obstruction of small pulmonary arteries, leading to right ventricular failure and, ultimately, death. One established risk factor for the development of PAH is HIV infection. The presence of PAH is an independent risk factor for mortality in HIV-infected patients. This article will focus on HIV-associated PAH (HIV-PAH) with special considerations to the available treatments. With the approval of the soluble guanylate cyclase stimulator riociguat, a new drug class has become available in addition to the already existing prostanoids, endothelin receptor antagonists, and phosphodiesterase type 5 inhibitors. Guidelines for the treatment of idiopathic PAH and guidelines for antiretroviral therapy should be followed for the treatment of HIV-PAH.

HIV related pulmonary arterial hypertension: epidemiology in Africa, physiopathology, and role of antiretroviral treatment

The development of HIV related pulmonary arterial hypertension (PAH) reduces the probability of survival by half as compared with HIV-infected individuals without HIV related PAH. HIV infected patients have a greater incidence of PAH compared to general population and have a 2500-fold increased risk of developing PAH. It is therefore important to have a recent overview of the problem in Africa, the most HIV affected part of the world (70 % of all HIV infection in the world). First, we discussed the epidemiology of HIV-related PAH in Africa. Second, the current understanding of the HIV-related PAH pathogenesis has been covered. Third, role of highly active antiretroviral therapy on HIV-related PAH has been revisited. There are few data concerning epidemiology of HIV related pulmonary hypertension in Africa leading to necessity to conduct further prospective large studies. The prevalence of PAH among HIV infected people in Africa varies from 5 to 13 %. The prevalence of HIV-related PAH in Africa is notably high compared to those in developed countries and in general population. The pathogenesis of PAH is clearly complex, and probably results from the interaction of multiple modulating genes with environmental factors. The physiopathology includes cytokines secretion increase which induces dysregulation of endothelial and vascular smooth muscle cell growth and imbalance of endogenous vasodilators and constrictors; HIV viral proteins which induces vascular oxidative stress, smooth myocyte proliferation and migration, and endothelial injury and genetic predisposition due to some major histocompatibility complex alleles, particularly HDL-DR6 and HLA-DR5. Histologically, HIV related PAH has the same characteristics with other types PAH. Antiretroviral therapy have a beneficial effect on the outcome of HIV related pulmonary hypertension, but it lacks evidence from large prospective studies.

Noninfectious pulmonary complications of human immunodeficiency virus infection

Human immunodeficiency virus type 1 (HIV-1) is the retrovirus responsible for the development of AIDS. Its profound impact on the immune system leaves the host vulnerable to a wide range of opportunistic infections not seen in individuals with a competent immune system. Pulmonary infections dominated the presentations in the early years of the epidemic, and infectious and noninfectious lung diseases remain the leading causes of morbidity and mortality in persons living with HIV despite the development of effective antiretroviral therapy. In addition to the long known immunosuppression and infection risks, it is becoming increasingly recognized that HIV promotes the risk of noninfectious pulmonary diseases through a number of different mechanisms, including direct tissue toxicity by HIV-related viral proteins and the secondary effects of coinfections. Diseases of the airways, lung parenchyma and the pulmonary vasculature, as well as pulmonary malignancies, are either more frequent in persons living with HIV or have atypical presentations. As the pulmonary infectious complications of HIV are generally well known and have been reviewed extensively, this review will focus on the breadth of noninfectious pulmonary diseases that occur in HIV-infected individuals as these may be more difficult to recognize by general medical physicians and subspecialists caring for this large and uniquely vulnerable population.

Tat predominantly associates with host promoter elements in HIV-1-infected T-cells - regulatory basis of transcriptional repression of c-Rel

HIV-1 Tat is a multifunctional regulatory protein that, in addition to its primary function of transactivating viral transcription, also tends to modulate cellular gene expression, for which the molecular mechanism remains to be clarified. We have reported earlier nuclear factor kappa B (NFκB) enhancer binding activity of Tat and proposed this DNA binding activity as a possible molecular basis for Tat-mediated regulation of cellular gene expression in infected cells. In the present study, we analyzed the genome-wide occupancy of Tat protein on host cell chromatin in HIV-1-infected T-cells to investigate a potential role of Tat on cellular gene expression. The results obtained identify a spectrum of binding sites of Tat protein on the chromatin and reveal that Tat is also recruited on a number of cellular gene promoters in HIV-1-infected T-cells, indicating its possible involvement in the regulation of gene expression of such cellular genes. Tat was identified as a repressor of one such validated gene, c-Rel, because it downregulates the expression of c-Rel in both Tat expressing and HIV-1-infected T-cells. The results also show that Tat downregulates c-Rel promoter activity by interacting with specific NFκB sites on the c-Rel promoter, thus providing a molecular basis of Tat-mediated regulation of cellular gene expression. Thus, in the present study, we have not only identified recruitment sites of Tat on the chromatin in HIV-1-infected T-cells, but also report for the first time that c-Rel is downregulated in HIV-1-infected cells specifically by interaction of Tat with NFκB binding sites on the promoter.

The burden of pulmonary hypertension in resource-limited settings

Pulmonary vascular disease (PVD) is a significant global health problem and accounts for a substantial portion of cardiovascular disease in the developing world. Although there have been considerable advances in therapeutics for pulmonary arterial hypertension, over 97% of the disease burden lies within the developing world where there is limited access to health care and pharmaceuticals. The causes of pulmonary arterial hypertension differ between industrialized and developing nations. Infectious diseases-including schistosomiasis human immunodeficiency virus, and rheumatic fever-are common causes of PVD, as are hemoglobinopathies, and untreated congenital heart disease. High altitude and exposure to household air pollutants also contribute to a significant portion of PVD cases. Although diagnosis of pulmonary arterial hypertension requires the use of imaging and invasive hemodynamics, access to equipment may be limited. PVD therapies may be prohibitively expensive and limited to a select few. Prevention is therefore important in limiting the global PVD burden.

Pulmonary arterial hypertension in HIV infection: a concise review

Pulmonary arterial hypertension (PAH) is an infrequent but nevertheless serious life threatening severe complication of human immunodeficiency virus (HIV) infection. In today's era of antiretroviral therapy (ART), the mortality of HIV patients has greatly reduced due to improved immune function and fewer opportunistic infections. However, these patients have an increased incidence of PAH. In this review, we will mainly discuss HIV-related pulmonary arterial hypertension (HRPH) in terms of the epidemiology, pathogenesis, clinical characteristics and treatment.

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.

Human immunodeficiency virus and pulmonary arterial hypertension

Human immunodeficiency virus- (HIV-) related pulmonary arterial hypertension (PAH) is a rare complication of HIV infection. The pathophysiology of HIV-related PAH is complex, with viral proteins seeming to play the major role. However, other factors, such as coinfection with other microorganisms and HIV-related systemic inflammation, might also contribute. The clinical presentation of HIV-related PAH and diagnosis is similar to other forms of pulmonary hypertension. Both PAH-specific therapies and HAART are important in HIV-related PAH management. Future studies investigating the pathogenesis are needed to discover new therapeutic targets and treatments.

Human immunodeficiency virus-associated pulmonary arterial hypertension

Antiretroviral therapy has greatly increased longevity for individuals with human immunodeficiency virus (HIV) infection. About 0.5% of patients with HIV infection develop moderate to severe pulmonary arterial hypertension, which is several thousand times higher than the incidence of idiopathic pulmonary arterial hypertension. As more than 30 million individuals are chronically infected, HIV infection could soon become one of the most common causes of pulmonary arterial hypertension worldwide. Pulmonary arterial hypertension is a relentlessly progressive disease leading to right heart failure and death. In this article the available data on epidemiology, hemodynamics, mechanisms, and therapeutic strategies for HIV-associated pulmonary arterial hypertension are reviewed.

[Pulmonary hypertension in patients infected with human immunodeficiency virus: current situation]

The increase in survival that has been achieved with the new treatments in the era of highly active antiretroviral therapy, has enabled clinicians and researchers to analyze issues that emerge in the long term in patients with HIV infection. Although the majority of cardiovascular complications have been widely described, the pathogenesis of pulmonary arterial hypertension is still poorly understood, and is one of the more complex and feared complications as it worsens the prognosis and quality of life of these patients This article reviews newer aspects related to the aetiology, symptoms, diagnosis and treatment of this disease.

Inflammation in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling of the precapillary pulmonary arteries, with excessive proliferation of vascular cells. Although the exact pathophysiology remains unknown, there is increasing evidence to suggest an important role for inflammation. Firstly, pathologic specimens from patients with PAH reveal an accumulation of perivascular inflammatory cells, including macrophages, dendritic cells, T and B lymphocytes, and mast cells. Secondly, circulating levels of certain cytokines and chemokines are elevated, and these may correlate with a worse clinical outcome. Thirdly, certain inflammatory conditions such as connective tissue diseases are associated with an increased incidence of PAH. Finally, treatment of the underlying inflammatory condition may alleviate the associated PAH. Underlying pathologic mechanisms are likely to be "multihit" and complex. For instance, the inflammatory response may be regulated by bone morphogenetic protein receptor type 2 (BMPR II) status, and, in turn, BMPR II expression can be altered by certain cytokines. Although antiinflammatory therapies have been effective in certain connective-tissue-disease-associated PAH, this approach is untested in idiopathic PAH (iPAH). The potential benefit of antiinflammatory therapies in iPAH is of importance and requires further study.

Bone morphogenetic protein receptor 2 in patients with idiopathic portal hypertension

In idiopathic portal hypertension (IPH) typical vascular lesions are present in the branches of the portal vein or in the perisinusoidal area of the liver. Similar histological alterations have been reported in the pulmonary vasculature of patients with idiopathic pulmonary artery hypertension (IPAH). As IPAH is associated with mutations of the bone morphogenetic protein receptor 2 (BMPR2) gene, the aim of this study was to investigate whether this association might also be found in patients with IPH. Twenty-three samples belonging to 21 unrelated caucasian patients with IPH followed in the hepatic haemodynamic laboratory of the Hospital Clinic in Barcelona were included in the study. All patients were studied for the entire open reading frame and splice site of the BMPR2 gene by direct sequencing and multiple ligation probe amplification (MLPA) in order to detect large deletions/duplications. None of the 23 patients had pulmonary artery hypertension. Four patients presented one single nucleotide polymorphism (SNP) in intron 5, four patients had a SNP in exon 12 and a SNP in exon 1 was found in two cases. Two patients had both intron 5 and exon 12 polymorphisms. All SNPs were previously described. Except for these three SNPs, neither mutations nor rearrangements have been identified in the BMPR2 gene in this population. We did not detect mutations or rearrangements in the coding region of the BMPR2 gene in our patients with IPH. These findings suggest that, in contrast to IPAH, mutations in BMPR2 are not involved in the pathogenesis of IPH.

Human immunodeficiency virus transgenic rats exhibit pulmonary hypertension

Human immunodeficiency virus (HIV)-associated pulmonary arterial hypertension (PAH) is a serious noninfectious disease involving an aberrant increase in pressure in the blood vessels of the lung, which leads to right ventricular (RV) heart failure and can eventually result in death. A lack of viable animal models of HIV-PAH has limited the identification of signaling pathways involved in HIV-mediated onset and progression of PAH. To determine whether the HIV-1 transgenic (HIV Tg) rat displays pathophysiological end points associated with PAH, we evaluated peak RV systolic pressure (RVSP), RV hypertrophy, pulmonary vessel remodeling, and alterations in gene expression by real-time PCR and microarray. RVSP was measured by RV catheterization via the right jugular vein in 3- and 9-mo-old HIV Tg and age-matched Fischer 344 (control) male rats while under 2% isoflurane anesthesia. RVSP was elevated in the HIV Tg rats (34.2 ± 2.5 mmHg) compared with the F344 controls (21.2 ± 2.5 mmHg), with more significant elevations in the 9-mo-old HIV Tg rats (42.5 ± 3.7 mmHg). We observed significant increases in RV wall thickness in HIV Tg rats compared with controls, both histologically and by echocardiograph measurement. HIV Tg rats also show increased thickening of the pulmonary artery and remodeling of small pulmonary arteries, as well as altered expression of gene pathways associated with PAH. These data represent the first analysis of PAH in HIV Tg rats and suggest that this model will be useful for investigating pathways and identifying potential therapies for HIV-PAH.

HIV infection and pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare but severe disease that results from chronic obstruction of small pulmonary arteries, leading to right ventricular failure and, ultimately, death. One established risk factor for the development of PAH is HIV infection. In comparison with the incidence of idiopathic PAH in the general population (1-2 per million), HIV-infected patients have a 2500-fold increased risk of developing PAH. The presence of PAH is an independent risk factor for mortality in patients with HIV infection, and in most cases death is causally related to PAH rather than to other complications of HIV infection. This article will focus on HIV-PAH with special considerations to epidemiology, pathogenesis, clinical presentation, diagnostic approach and available treatments.

Pulmonary vascular lesions are common in SIV- and SHIV-env-infected macaques

The lack of animal models of HIV-related pulmonary arterial hypertension (HIV-PAH) severely limits investigation of this serious disease. While histological evidence of HIV-PAH has been demonstrated in macaques infected with simian immunodeficiency virus (SIV) as well as with chimeric simian/human immunodeficiency virus (SHIV) containing HIV-1-derived Nef protein, other primate models have not been studied. The objective was to document and describe the development of pulmonary vascular changes in macaques infected with SIV or with SIV containing HIV-1-derived envelope protein (SHIV-env). Lung tissue was obtained at necropsy from 13 SHIV (89.6P)-env-infected macaques and 10 SIV (ΔB670)-infected macaques. Pulmonary arterial pathology, including arterial hyperplasia and the presence of plexiform lesions, was compared to normal monkey lung. Pulmonary artery hyperplasia was present in 8 of 13 (62%) SHIV-env-infected macaques and 4/10 (36%) SIV-infected macaques. The most common histopathological lesions were intimal and medial hyperplasia of medium and large pulmonary arteries. Hyperplastic lesions were predominantly due to smooth muscle cell hyperplasia. This is the first report of pulmonary vascular lesions in SHIV-env-infected macaques and confirms prior reports of pulmonary vasculopathy in SIV-infected macaques. The finding of pulmonary arteriopathy in monkeys infected with SHIV not containing HIV-nef suggests that other factors might also be important in the development of HIV-PAH. This SHIV-env model provides a new means to investigate HIV-PAH.

Pulmonary hypertension associated with HIV infection: pulmonary vascular disease: the global perspective

The success of antiretroviral therapies in improving the survival of patients infected with HIV and reducing HIV-associated opportunistic infections is undisputed. Nevertheless, long-term outcomes such as noninfectious cardiovascular complications, including cardiomegaly, pericarditis, myocarditis, and pulmonary arterial hypertension, are now serious concerns. The lung is a frequent target organ for disorders associated with HIV infection. HIV-related pulmonary arterial hypertension (HRPAH) affects more individuals who are infected with HIV than individuals who are uninfected. Moreover, the long-standing estimated prevalence of HRPAH in developed countries (calculated at 0.5%) is increasing as more clinician-scientists unify their efforts to screen patients who are pulmonary asymptomatic for pulmonary arterial hypertension. In order to decrease mortality, efforts are directed at early detection, diagnosis, and therapeutic interventions before the disease compromises patients' quality of life. This article reviews the logistics of screening approaches for HRPAH and discusses the substantial disease burden currently faced by developing countries, where the prevalence of HIV infection is higher and complicated by hyperendemic risk factors, limited access to antiretrovirals, and lack of screening tools. We also present mechanistic insights into HRPAH, including the role of HIV proteins and their potential use as screening tools, and, finally, areas that still need intense research.

Differential regulation of indoleamine-2,3-dioxygenase (IDO) by HIV type 1 clade B and C Tat protein

Previous studies have demonstrated that infection with HIV-1 clades might differentially contribute to the neuropathogenesis of HIV-1-associated dementia (HAD). HIV-1 transactivator regulatory protein (Tat) plays a major role in the process of disruption of neuronal function. It is not well understood how these HIV-1 subtypes exert different neuropathogenic effects. Activation of indoleamine-2,3-dioxygenase (IDO), the rate-limiting enzyme of the kynurenine pathway, leads to increased tryptophan catabolism and the generation of neurotoxins such as kynurenine (KYN). It is known that KYN plays a crucial role in the neuropathogenesis of HAD. We hypothesize that HIV-1 clade B and C Tat proteins might exert differential effects on human primary astrocytes by the upregulation of the IDO gene and protein expression as well as its activity and production of the neurotoxin KYN. RNA extracted from human primary astrocytes treated with either HIV-1 clade B and C Tat proteins was reverse transcribed and analyzed by quantitative real-time PCR to determine IDO gene expression. In addition, the enzymatic activity of IDO and the concentration of KYN were measured in cell lysates and culture supernatants. Our results indicate that HIV-1 clade B Tat protein significantly upregulated the IDO gene and protein expression, IDO enzyme activity, as well as KYN concentration compared to HIV-1 clade C Tat protein. Thus, our studies for the first time demonstrate that HIV-1 clade B Tat protein in human primary astrocytes appears to increase the level of neuropathogenic agents, such as IDO and KYN, as compared to HIV-1 clade C Tat protein. These results provide further evidence that the prevalence of HAD may be correlated with the difference in clades of HIV-1.

Pathogenic mechanisms of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a complex disease that causes significant morbidity and mortality and is clinically characterized by an increase in pulmonary vascular resistance. The histopathology is marked by vascular proliferation/fibrosis, remodeling, and vessel obstruction. Development of PAH involves the complex interaction of multiple vascular effectors at all anatomic levels of the arterial wall. Subsequent vasoconstriction, thrombosis, and inflammation ensue, leading to vessel wall remodeling and cellular hyperproliferation as the hallmarks of severe disease. These processes are influenced by genetic predisposition as well as diverse endogenous and exogenous stimuli. Recent studies have provided a glimpse at certain molecular pathways that contribute to pathogenesis; these have led to the identification of attractive targets for therapeutic intervention. We will review our current understanding of the mechanistic underpinnings of the genetic and exogenous/acquired triggers of PAH. The resulting imbalance of vascular effectors provoking pathogenic vascular changes will also be discussed, with an emphasis on common and overarching regulatory pathways that may relate to the primary triggers of disease. The current conceptual framework should allow for future studies to refine our understanding of the molecular pathogenesis of PAH and improve the therapeutic regimen for this disease.

Emerging therapies for pulmonary arterial hypertension

Pulmonary arterial hypertension is characterised by increased pulmonary vascular resistance due to increased vascular tone and structural remodelling of pulmonary vessels. The therapies that are in use so far have been developed to correct endothelial dysfunction and reduce vasomotor tone. These treatments have a limited effect on the remodelling process and, increasingly, the focus is turning to potent strategies for inhibiting vascular proliferation and promoting vascular apoptosis. Multiple novel targets have been uncovered over the last 5 years and several are now in early clinical trials. At present, it is clear that there is no single treatment for the condition. Although this is the case, studies are investigating the role of combining therapies that are already established.

HIV-1 Tat interaction with cyclin T1 represses mannose receptor and the bone morphogenetic protein receptor-2 transcription

Macrophage transcription is significantly altered by HIV-1 infection. HIV Tat, an immediate-early product of the viral lifecycle, interacts with host transcription factors to alter host gene expression. We have previously shown that Tat represses transcription from the mannose receptor (MR) and the bone morphogenetic protein receptor-2 (BMPR2) promoters. The current study shows that transcriptional repression of these receptors involves Tat interaction with cyclin T1. Assays using U937 human monocytic cells transiently expressing MR or BMPR2 promoter-luciferase constructs demonstrated equal repression by one- and two-exon Tat gene products. A mutant Tat expression vector encoding Tat protein lacking the cyclin T1 binding domain failed to inhibit MR and BMPR2 promoter activities. Over-expression of cyclin T1 in the presence of wild-type Tat resulted in recovered activity from both promoters. Finally, two inhibitors of cyclin-dependent kinase 9 (a dominant negative CDK9 and flavopiridol) repressed activity from the MR and BMPR2 promoters.