HIV-1-transgene expression in rats decreases alveolar macrophage zinc levels and phagocytosis

Granulocyte macrophage colony stimulating factor in virus-host interactions and its implication for immunotherapy

Viruses have evolved to strategically exploit cellular signaling pathways to evade host immune defenses. GM-CSF signaling plays a pivotal role in regulating inflammation, activating myeloid cells, and enhancing the immune response to infections. Due to its central role in the immune system, viruses may target this pathway to further establish infection. This review focuses on key studies elucidating virus interactions with GM-CSF signaling proteins and summarizes findings on the impact of viral infections on GM-CSF production. Additionally, therapeutic strategies centered around GM-CSF are investigated, such as the potential benefits of administering GM-CSF versus inhibiting GM-CSF signaling to mitigate viral-induced aberrant inflammation. Understanding these virus-host interactions provides valuable insights that help further our understanding to develop future therapeutic approaches in modulating the immune response during viral infections.

Alveolar Macrophages in Viral Respiratory Infections: Sentinels and Saboteurs of Lung Defense

Respiratory viral infections continue to cause pandemic and epidemic outbreaks in humans and animals. Under steady-state conditions, alveolar macrophages (AlvMϕ) fulfill a multitude of tasks in order to maintain tissue homeostasis. Due to their anatomic localization within the deep lung, AlvMϕ are prone to detect and react to inhaled viruses and thus play a role in the early pathogenesis of several respiratory viral infections. Here, detection of viral pathogens causes diverse antiviral and proinflammatory reactions. This fact not only makes them promising research targets, but also suggests them as potential targets for therapeutic and prophylactic approaches. This review aims to give a comprehensive overview of the current knowledge about the role of AlvMϕ in respiratory viral infections of humans and animals.

The role of alveolar macrophages in viral respiratory infections and their therapeutic implications

Alveolar macrophages are pivotal components of the lung's innate immune defense against respiratory virus infections. Their multifaceted role spans from viral clearance to modulation of immune responses, making them essential players in shaping disease outcomes. In this comprehensive review collection, we look into the intricate interplay between Alveolar macrophages and various respiratory viruses, shedding light on their dynamic contributions to immune resilience. From influenza to respiratory syncytial virus, Alveolar macrophages emerge as sentinels of the airways, actively participating in viral detection and initiating rapid antiviral responses. Their ability to recognize viral pathogens triggers a cascade of events, including cytokine and chemokine production that guides the recruitment and activation of immune effectors. Furthermore, Alveolar macrophages impact the fate of adaptive immune responses by modulating the activation of T lymphocytes and the secretion of key cytokines. These reviews encompass a range of insights, including the regulation of inflammasome activation, the influence of Alveolar macrophages on cytokine dysregulation, and their role in preventing secondary bacterial pneumonia post-infection. Collectively, they highlight the significance of Alveolar macrophages in preserving pulmonary integrity and immune homeostasis during viral challenges.

Mitochondrial Metabolism in Alveolar Macrophages of Patients Infected with HIV, Tuberculosis, and HIV/Tuberculosis

Tuberculosis (TB) is one of the most common opportunistic infections and is a leading cause of mortality in patients with HIV and AIDS. HIV infection causes serious defects in the host immune system and increases the risk of active TB. TB infection promotes HIV replication and aggravates host damage in patients with HIV/AIDS. Alveolar macrophages (AMs) are essential immune cells during TB and HIV infections. AMs undergo a shift in mitochondrial metabolism during TB or HIV infection, that is, metabolic reprogramming, allowing them to act in the form of classical activated macrophages (M1) and alternative activated macrophages (M2) at different stages of infection. We reviewed the alterations in the mitochondrial energy metabolism of AMs in patients with HIV, TB, and HIV/TB to provide ideas for further research on the role of metabolic reprogramming by AMs in the pathogeneses of HIV, TB, and HIV/TB coinfection.

HIV-associated lung disease

Lung disease encompasses acute, infectious processes and chronic, non-infectious processes such as chronic obstructive pulmonary disease, asthma and lung cancer. People living with HIV are at increased risk of both acute and chronic lung diseases. Although the use of effective antiretroviral therapy has diminished the burden of infectious lung disease, people living with HIV experience growing morbidity and mortality from chronic lung diseases. A key risk factor for HIV-associated lung disease is cigarette smoking, which is more prevalent in people living with HIV than in uninfected people. Other risk factors include older age, history of bacterial pneumonia, Pneumocystis pneumonia, pulmonary tuberculosis and immunosuppression. Mechanistic investigations support roles for aberrant innate and adaptive immunity, local and systemic inflammation, oxidative stress, altered lung and gut microbiota, and environmental exposures such as biomass fuel burning in the development of HIV-associated lung disease. Assessment, prevention and treatment strategies are largely extrapolated from data from HIV-uninfected people. Smoking cessation is essential. Data on the long-term consequences of HIV-associated lung disease are limited. Efforts to continue quantifying the effects of HIV infection on the lung, especially in low-income and middle-income countries, are essential to advance our knowledge and optimize respiratory care in people living with HIV.

Granulocyte Macrophage-Colony Stimulating Factor Reverses HIV Protein-Induced Mitochondrial Derangements in Alveolar Macrophages

Despite the advent of antiretroviral therapy, people living with HIV suffer from a range of infectious and noninfectious pulmonary complications. HIV impairs antioxidant defenses and innate immune function of the alveolar macrophage by diminishing granulocyte macrophage-colony stimulating factor (GM-CSF) signaling. Since GM-CSF may be linked to mitochondria, we sought to determine the effects of HIV on GM-CSF receptor expression and alveolar macrophage mitochondrial function. At an academic medical center, studies were completed on alveolar macrophages isolated from both wild-type and HIV transgenic (HIV Tg) rats and human subjects with and without HIV. Primary macrophages were plated and evaluated for expression of GM-CSF receptor beta, phagocytic index, and mitochondrial function in the presence and absence of GM-CSF treatment. GM-CSF receptor expression and mitochondrial function were impaired in macrophages isolated from HIV Tg rats, and treatment with GM-CSF restored GM-CSF receptor expression and mitochondrial function. GM-CSF treatment of HIV Tg rats also increased alveolar macrophage levels of the mitochondrial proteins voltage-dependent anion-selective channel 1 (VDAC) and glucose-regulated protein 75 (Grp75). Similar to the HIV Tg rat model, impairments in mitochondrial bioenergetics were confirmed in alveolar macrophages isolated from human subjects with HIV. HIV-associated impairments in alveolar macrophage mitochondrial bioenergetics likely contribute to innate immune dysfunction in HIV infection, and GM-CSF treatment may offer a novel therapeutic strategy for mitigating these deleterious effects.

Heme attenuates beta-endorphin levels in leukocytes of HIV positive individuals with chronic widespread pain

The prevalence of chronic widespread pain (CWP) in people with HIV is high, yet the underlying mechanisms are elusive. Leukocytes synthesize the endogenous opioid, β-endorphin, within their endoplasmic reticulum (ER). When released into plasma, β-endorphin dampens nociception by binding to opioid receptors on sensory neurons. We hypothesized that the heme-dependent redox signaling induces ER stress, which attenuates leukocyte β-endorphins levels/release, thereby increasing pain sensitivity in people with HIV. Results demonstrated that HIV positive individuals with CWP had increased plasma methemoglobin, erythrocytes membrane oxidation, hemolysis, and low plasma heme scavenging enzyme, hemopexin, compared to people with HIV without CWP and HIV-negative individuals with or without pain. In addition, the leukocytes from people with HIV with CWP had attenuated levels of the heme metabolizing enzyme, heme oxygenase-1, which metabolizes free heme to carbon-monoxide and biliverdin. These individuals also had elevated ER stress, and low β-endorphin in leukocytes. In vitro, heme exposure or heme oxygenase-1 deletion, decreased β-endorphins in murine monocytes/macrophages. Treating cells with a carbon-monoxide donor or an ER stress inhibitor, increased β-endorphins. To mimic hemolytic effects in a preclinical model, C57BL/6 mice were injected with phenylhydrazine hydrochloride (PHZ). PHZ increased cell-free heme and ER stress, decreased leukocyte β-endorphin levels and hindpaw mechanical sensitivity thresholds. Treatment of PHZ-injected mice with hemopexin blocked these effects, suggesting that heme-induced ER stress and a subsequent decrease in leukocyte β-endorphin is responsible for hypersensitivity in people with HIV.

HIV Impairs Alveolar Macrophage Function via MicroRNA-144-Induced Suppression of Nrf2

BACKGROUND

Despite anti-retroviral therapy, HIV-1 infection increases the risk of pneumonia and causes oxidative stress and defective alveolar macrophage (AM) immune function. We have previously determined that HIV-1 proteins inhibit antioxidant defenses and impair AM phagocytosis by suppressing nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Given its known effects on Nrf2, we hypothesize miR-144 mediates the HIV-1 induced suppression of Nrf2.

METHODS

Primary AMs isolated from HIV-1 transgenic (HIV-1 Tg) rats and wild type littermates (WT) as well as human monocyte-derived macrophages (MDMs) infected ex vivo with HIV-1 were used. We modulated miR-144 expression using a miR-144 mimic or an inhibitor to assay its effects on Nrf2/ARE activity and AM functions in vitro and in vivo.

RESULTS

MiR-144 expression was increased in AMs from HIV-1 Tg rats and in HIV-1-infected human MDMs compared to cells from WT rats and non-infected human MDMs, respectively. Increasing miR-144 with a miR-144 mimic inhibited the expression of Nrf2 and its downstream effectors in WT rat macrophages and consequently impaired their bacterial phagocytic capacity and H₂O₂ scavenging ability. These effects on Nrf2 expression and AM function were reversed by antagonizing miR-144 ex vivo or in the airways of HIV-1 Tg rats in vivo, but this protection was abrogated by silencing Nrf2 expression.

CONCLUSIONS

Our results suggest that inhibiting miR-144 or interfering with its deleterious effects on Nrf2 attenuates HIV-1-mediated AM immune dysfunction and improves lung health in individuals with HIV.

Pathogenesis of HIV-Related Lung Disease: Immunity, Infection, and Inflammation

Despite anti-retroviral therapy (ART), human immunodeficiency virus-1 (HIV)-related pulmonary disease continues to be a major cause of morbidity and mortality for people living with HIV (PLWH). The spectrum of lung diseases has changed from acute opportunistic infections resulting in death to chronic lung diseases for those with access to ART. Chronic immune activation and suppression can result in impairment of innate immunity and progressive loss of T cell and B cell functionality with aberrant cytokine and chemokine responses systemically as well as in the lung. HIV can be detected in the lungs of PLWH and has profound effects on cellular immune functions. In addition, HIV-related lung injury and disease can occur secondary to a number of mechanisms including altered pulmonary and systemic inflammatory pathways, viral persistence in the lung, oxidative stress with additive effects of smoke exposure, microbial translocation, and alterations in the lung and gut microbiome. Although ART has had profound effects on systemic viral suppression in HIV, the impact of ART on lung immunology still needs to be fully elucidated. Understanding of the mechanisms by which HIV-related lung diseases continue to occur is critical to the development of new preventive and therapeutic strategies to improve lung health in PLWH.

MiR-144 mediates Nrf2 inhibition and alveolar epithelial dysfunction in HIV-1 transgenic rats

Chronic HIV infection causes redox stress and increases the risk of acute and chronic lung injury, even when individuals are adherent to antiretroviral therapy. HIV-1 transgene expression in rats inhibits nuclear factor (erythroid-derived 2)-like 2 (Nrf2), which regulates antioxidant defenses and alveolar epithelial cell (AEC) barrier function, but the mechanism is unknown. In this study, we present novel evidence that these pathological effects of HIV are mediated by microRNA-144 (miR-144). HIV-1 transgene expression in vivo increases the expression of miR-144 in the alveolar epithelium, and this can be replicated by direct exposure of naïve primary AECs to either Tat or gp120 ex vivo. Further, treating naïve primary AECs with a miR-144 mimic decreased the expression and activity of Nrf2 and inhibited their barrier formation. In contrast, treatment with a miR-144 antagomir increased the expression and activity of Nrf2 and improved barrier function in primary AECs isolated from HIV-1 transgenic rats. Importantly, either delivering the miR-144 antagomir intratracheally, or directly activating Nrf2 by dietary treatment with PB123, increased Nrf2 expression and barrier formation in HIV-1 transgenic rat AECs. This study provides new experimental evidence that HIV-induced inhibition of Nrf2 and consequent AEC barrier dysfunction are mediated via miR-144, and that these pathophysiological effects can be mitigated in vivo by either directly antagonizing miR-144 or activating Nrf2. Our findings suggest that targeting the inhibition of Nrf2 in individuals living with HIV could enhance their lung health and decrease the lung-specific morbidity and mortality that persists despite antiretroviral therapy.

The Role of Zinc and Zinc Homeostasis in Macrophage Function

Zinc has long been recognized as an essential trace element, playing roles in the growth and development of all living organisms. In recent decades, zinc homeostasis was also found to be important for the innate immune system, especially for maintaining the function of macrophages. It is now generally accepted that dysregulated zinc homeostasis in macrophages causes impaired phagocytosis and an abnormal inflammatory response. However, many questions remain with respect to the mechanisms that underlie these processes, particularly at the cellular and molecular levels. Here, we review our current understanding of the roles that zinc and zinc transporters play in regulating macrophage function.

Therapeutic Modulation of Virus-Induced Oxidative Stress via the Nrf2-Dependent Antioxidative Pathway

Virus-induced oxidative stress plays a critical role in the viral life cycle as well as the pathogenesis of viral diseases. In response to reactive oxygen species (ROS) generation by a virus, a host cell activates an antioxidative defense system for its own protection. Particularly, a nuclear factor erythroid 2p45-related factor 2 (Nrf2) pathway works in a front-line for cytoprotection and detoxification. Recently, a series of studies suggested that a group of clinically relevant viruses have the capacity for positive and negative regulations of the Nrf2 pathway. This virus-induced modulation of the host antioxidative response turned out to be a crucial determinant for the progression of several viral diseases. In this review, virus-specific examples of positive and negative modulations of the Nrf2 pathway will be summarized first. Then a number of successful genetic and pharmacological manipulations of the Nrf2 pathway for suppression of the viral replication and the pathogenesis-associated oxidative damage will be discussed later. Understanding of the interplay between virus-induced oxidative stress and antioxidative host response will aid in the discovery of potential antiviral supplements for better management of viral diseases.

Dysregulation of Alveolar Macrophage PPARγ, NADPH Oxidases, and TGFβ1 in Otherwise Healthy HIV-Infected Individuals

Despite antiretroviral therapy (ART), respiratory infections increase mortality in individuals living with chronic human immunodeficiency virus (HIV) infection. In experimental and clinical studies of chronic HIV infection, alveolar macrophages (AMs) exhibit impaired phagocytosis and bacterial clearance. Peroxisome proliferator-activated receptor (PPAR)γ, NADPH oxidase (Nox) isoforms Nox1, Nox2, Nox4, and transforming growth factor-beta 1 (TGFβ₁) are critical mediators of AM oxidative stress and phagocytic dysfunction. Therefore, we hypothesized that HIV alters AM expression of these targets, resulting in chronic lung oxidative stress and subsequent immune dysfunction. A cross-sectional study of HIV-infected (n = 22) and HIV-uninfected (n = 6) subjects was conducted. Bronchoalveolar lavage (BAL) was performed, and AMs were isolated. Lung H₂O₂ generation was determined by measuring H₂O₂ in the BAL fluid. In AMs, PPARγ, Nox1, Nox2, Nox4, and TGFβ₁ mRNA (quantitative real-time polymerase chain reaction) and protein (fluorescent immunomicroscopy) levels were assessed. Compared with HIV-uninfected (control) subjects, HIV-infected subjects were relatively older and the majority were African American; ∼86% were on ART, and their median CD4 count was 445, with a median viral load of 0 log copies/ml. HIV infection was associated with increased H₂O₂ in the BAL, decreased AM mRNA and protein levels of PPARγ, and increased AM mRNA and protein levels of Nox1, Nox2, Nox4, and TGFβ₁. PPARγ attenuation and increases in Nox1, Nox2, Nox4, and TGFβ₁ contribute to AM oxidative stress and immune dysfunction in the AMs of otherwise healthy HIV-infected subjects. These findings provide novel insights into the molecular mechanisms by which HIV increases susceptibility to pulmonary infections.

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.

HIV-1 decreases Nrf2/ARE activity and phagocytic function in alveolar macrophages

Respiratory complications occur frequently in individuals living with human immunodeficiency-1 virus (HIV) infection, and there is evidence that HIV-related oxidative stress impairs alveolar macrophage immune function. We hypothesized that nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a master transcription factor that activates the antioxidant response element (ARE) and regulates antioxidant defenses, has an important role in alveolar macrophage (AMs) immune dysfunction in individuals with HIV infections. To test that hypothesis, we analyzed human monocyte-derived macrophages (MDMs) that were either infected with HIV-1 or were exposed to the HIV-related proteins gp120 and Tat ex vivo and determined that either stress affected the expression of Nrf2 and the Nrf2-ARE-dependent genes for NAD(P)H dehydrogenase, quinone 1 (NQO1) and glutamate-cysteine ligase, catalytic subunit (GCLC). We then determined that the expression of Nrf2, NQO1, and GCLC was significantly decreased in primary AMs isolated from HIV-1 transgenic rats. In parallel, treating a rat macrophage cell line (NR8383 cells) with the HIV-related proteins gp120 or Tat similarly decreased the gene and protein expression of Nrf2, NQO1, and GCLC. Further, phagocytic function was decreased in both human MDMs infected with HIV-1 and primary AMs from HIV-1 transgenic rats. Importantly, treating HIV-1-infected human MDMs or AMs from HIV-1 transgenic rats with sulforaphane (SFN, an Nrf2 activator) significantly improved their phagocytic function. The salutary effects of SFN were abrogated by silencing RNA to Nrf2 in wild-type rat macrophages. Our findings demonstrate that HIV-1 infection and exposure to HIV-1-related proteins inhibit Nrf2-ARE activity in the AMs and impair their phagocytic function. Treatments targeted at increasing Nrf2-ARE activity could, therefore, enhance lung innate immunity in people living with HIV-1.

Pulmonary Innate Immune Dysfunction in Human Immunodeficiency Virus

The advent of antiretroviral therapy has transformed infection by the type 1 human immunodeficiency virus (HIV) from a rapidly fatal disease to a chronic illness with excellent long-term survival rates. Although HIV primarily targets the adaptive arm of host immunity, it simultaneously impacts the innate immune system, and has profound implications for lung health, even when viral suppression is achieved with antiretroviral therapy. The lung has evolved a unique array of innate immune defenses, and the pathophysiological interactions between HIV and the pulmonary innate immune system deserve particular attention. In this review, we discuss work that elucidates how the components of innate immunity both respond to and are perturbed by infection with HIV.

HIV-related proteins prolong macrophage survival through induction of Triggering receptor expressed on myeloid cells-1

Triggering receptor expressed on myeloid cells-1(TREM-1) is a member of the superimmunoglobulin receptor family. We have previously shown that TREM-1 prolongs survival of macrophages treated with lipoolysaccharide through Egr2-Bcl2 signaling. Recent studies suggest a role for TREM-1 in viral immunity. Human immunodeficiency virus-1 (HIV) targets the monocyte/macrophage lineage at varying stages of infection. Emerging data suggest that macrophages are key reservoirs for latent HIV even in individuals on antiretroviral therapy. Here, we investigated the potential role of TREM-1 in HIV latency in macrophages. Our data show that human macrophages infected with HIV show an increased expression of TREM-1. In parallel, direct exposure to the HIV-related proteins Tat or gp120 induces TREM-1 expression in macrophages and confers anti-apoptotic attributes.NF-κB p65 silencing identified that these proteins induce TREM-1 in p65-dependent manner. TREM-1 silencing in macrophages exposed to HIV-related proteins led to increased caspase 3 activation and reduced Bcl-2 expression, rendering them susceptible to apotosis. These novel data reveal that TREM-1 may play a critical role in establishing HIV reservoir in macrophages by inhibiting apoptosis. Therefore, targeting TREM-1 could be a novel therapeutic approach to enhance clearance of the HIV reservoir, at least within the macrophage pools.

Characterization of neuropathology in the HIV-1 transgenic rat at different ages

The transgenic HIV-1 rat (Tg) is a commonly used neuroHIV model with documented neurologic/behavioral deficits. Using immunofluorescent staining of the Tg brain, we found astrocytic dysfunction/damage, as well as dopaminergic neuronal loss/dysfunction, both of which worsening significantly in the striatum with age. We saw mild microglial activation in young Tg brains, but this decreased with age. There were no differences in neurogenesis potential suggesting a neurodegenerative rather than a neurodevelopmental process. Gp120 CSF levels exceeded serum gp120 levels in some animals, suggesting local viral protein production in the brain. Further probing of the pathophysiology underlying astrocytic injury in this model is warranted.

The HIV-1 transgenic rat model of neuroHIV

Despite the ability of current combination anti-retroviral therapy (cART) to limit the progression of HIV-1 to AIDS, HIV-positive individuals continue to experience neuroHIV in the form of HIV-associated neurological disorders (HAND), which can range from subtle to substantial neurocognitive impairment. NeuroHIV may also influence substance use, abuse, and dependence in HIV-positive individuals. Because of the nature of the virus, variables such as mental health co-morbidities make it difficult to study the interaction between HIV and substance abuse in human populations. Several rodent models have been developed in an attempt to study the transmission and pathogenesis of the HIV-1 virus. The HIV-1 transgenic (HIV-1Tg) rat is a reliable model of neuroHIV because it mimics the condition of HIV-infected patients on cART. Research using this model supports the hypothesis that the presence of HIV-1 viral proteins in the central nervous system increases the sensitivity and susceptibility of HIV-positive individuals to substance abuse.

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.

Healthy HIV-1-infected individuals on highly active antiretroviral therapy harbor HIV-1 in their alveolar macrophages

In a prospective cross-sectional study we quantified HIV viral load within the alveolar macrophage in a cohort of healthy HIV-infected subjects who did not have medical comorbidities or smoke cigarettes to determine if alveolar macrophage proviral DNA was associated with alveolar macrophage phagocytic immune dysfunction. We enrolled 23 subjects who underwent bronchoscopy and bronchoalveolar lavage. Alveolar macrophages were isolated and HIV-1 RNA was quantified in the cells using the Abbott RealTime HIV-1 Assay. Proviral DNA was qualitatively measured using a modified version of the HIV-1 RNA assay. Phagocytosis measured by incubating alveolar macrophages with FITC-labeled Staphylococcus aureus and determining fluorescence with a Zeiss inverted microscope. Phagocytic index was calculated as (% positive cells × mean channel fluorescence)/100. Sixteen subjects had (+) proviral DNA and seven had (-) proviral DNA in their alveolar macrophages. Of all subjects 100% in both groups were on highly active antiretroviral therapy (HAART). The median plasma viral load was 0 in both groups. HIV-1-infected subjects with (+) proviral DNA in their alveolar macrophages had a significantly lower median alveolar macrophage phagocytic index compared to those with (-) proviral DNA in their alveolar macrophages [11.8 (IQR 4.8-39.0) vs. 64.9 (IQR 14.0-166.0), p = 0.05]. Alveolar macrophages harbor HIV even in otherwise healthy subjects with undetectable plasma viral loads, representing a potential reservoir for the virus. In addition, HIV viral replication within the macrophage may impair phagocytosis and other immune functions in the lung, leading to an increased risk for lung infection.

Zinc and zinc transporters in macrophages and their roles in efferocytosis in COPD

Our previous studies have shown that nutritional zinc restriction exacerbates airway inflammation accompanied by an increase in caspase-3 activation and an accumulation of apoptotic epithelial cells in the bronchioles of the mice. Normally, apoptotic cells are rapidly cleared by macrophage efferocytosis, limiting any secondary necrosis and inflammation. We therefore hypothesized that zinc deficiency is not only pro-apoptotic but also impairs macrophage efferocytosis. Impaired efferocytic clearance of apoptotic epithelial cells by alveolar macrophages occurs in chronic obstructive pulmonary disease (COPD), cigarette-smoking and other lung inflammatory diseases. We now show that zinc is a factor in impaired macrophage efferocytosis in COPD. Concentrations of zinc were significantly reduced in the supernatant of bronchoalveolar lavage fluid of patients with COPD who were current smokers, compared to healthy controls, smokers or COPD patients not actively smoking. Lavage zinc was positively correlated with AM efferocytosis and there was decreased efferocytosis in macrophages depleted of Zn in vitro by treatment with the membrane-permeable zinc chelator TPEN. Organ and cell Zn homeostasis are mediated by two families of membrane ZIP and ZnT proteins. Macrophages of mice null for ZIP1 had significantly lower intracellular zinc and efferocytosis capability, suggesting ZIP1 may play an important role. We investigated further using the human THP-1 derived macrophage cell line, with and without zinc chelation by TPEN to mimic zinc deficiency. There was no change in ZIP1 mRNA levels by TPEN but a significant 3-fold increase in expression of another influx transporter ZIP2, consistent with a role for ZIP2 in maintaining macrophage Zn levels. Both ZIP1 and ZIP2 proteins were localized to the plasma membrane and cytoplasm in normal human lung alveolar macrophages. We propose that zinc homeostasis in macrophages involves the coordinated action of ZIP1 and ZIP2 transporters responding differently to zinc deficiency signals and that these play important roles in macrophage efferocytosis.

HIV-1 transgenic rats display alterations in immunophenotype and cellular responses associated with aging

Advances in anti-retroviral therapy over the last two decades have allowed life expectancy in patients infected with the human immunodeficiency virus to approach that of the general population. The process of aging in mammalian species, including rats, results in immune response changes, alterations in immunological phenotypes, and ultimately increased susceptibility to many infectious diseases. In order to investigate the immunological pathologies associated with chronic HIV-1 disease, particularly in aging individuals, the HIV-1 transgenic (HIV-1Tg) rat model was utilized. HIV-1Tg rats were challenged with lipopolysaccharide (LPS) to determine immunological alterations during the aging process. LPS is known to cause an imbalance in cytokine and chemokine release, and provides a method to identify changes in immune responses to bacterial infection in an HIV animal model. An immune profile and accompanying cellular consequences as well as changes in inflammatory cytokine and chemokine release related to age and genotype were assessed in HIV-1Tg rats. The percentage of T cells decreased with age, particularly T cytotoxic cells, whereas T helper cells increased with age. Neutrophils and monocytes increased in HIV-1Tg rats during maturation compared to age-matched F344 control rats. Aging HIV-1Tg rats displayed a significant increase in the pro-inflammatory cytokines, IL-6 and TNF-α, along with an increase in the chemokine, KC/GRO, in comparison to age-matched controls. Our data indicate that immunophenotype and immune responses can change during aging in HIV-positive individuals. This information could be important in determining the most beneficial age-dependent therapeutic treatment for HIV patients.

The complexity of HIV persistence and pathogenesis in the lung under antiretroviral therapy: challenges beyond AIDS

Antiretroviral therapy (ART) represents a significant milestone in the battle against AIDS. However, we continue learning about HIV and confronting challenges 30 years after its discovery. HIV has cleverly tricked both the host immune system and ART. First, the many HIV subtypes and recombinant forms have different susceptibilities to antiretroviral drugs, which may represent an issue in countries where ART is just being introduced. Second, even under the suppressive pressures of ART, HIV still increases inflammatory mediators, deregulates apoptosis and proliferation, and induces oxidative stress in the host. Third, the preference of HIV for CXCR4 as a co-receptor may also have noxious outcomes, including potential malignancies. Furthermore, HIV still replicates cryptically in anatomical reservoirs, including the lung. HIV impairs bronchoalveolar T-lymphocyte and macrophage immune responses, rendering the lung susceptible to comorbidities. In addition, HIV-infected individuals are significantly more susceptible to long-term HIV-associated complications. This review focuses on chronic obstructive pulmonary disease (COPD), pulmonary arterial hypertension, and lung cancer. Almost two decades after the advent of highly active ART, we now know that HIV-infected individuals on ART live as long as the uninfected population. Fortunately, its availability is rapidly increasing in low- and middle-income countries. Nevertheless, ART is not risk-free: the developed world is facing issues with antiretroviral drug toxicity, resistance, and drug-drug interactions, while developing countries are confronting issues with immune reconstitution inflammatory syndrome. Several aspects of the complexity of HIV persistence and challenges with ART are discussed, as well as suggestions for new avenues of research.

Alcohol and HIV: Experimental and Clinical Evidence of Combined Impact on the Lung

Despite antiretroviral therapy, lung disease is a leading cause of death in individuals infected with human immunodeficiency virus type 1 (HIV). Individuals infected with HIV are susceptible to serious bacterial and viral infections, such as pneumococcus and influenza, which are particularly problematic for lung health, resulting in lung injury. Additionally, HIV-infected individuals are susceptible to a number of pulmonary diseases for unknown reasons. Alcohol, the most commonly abused drug in the world, continues to exact an enormous toll on morbidity and mortality in individuals living with HIV. Chronic alcohol abuse has been shown to affect lung immunity, resulting in significant lung injury. There is a paucity of literature on the additive effects of HIV and alcohol, two diseases of immune senescence, in the lung. This chapter begins by discussing the latest literature evaluating the epidemiology of HIV, alcohol use, and lung health focusing on two prevalent infections, tuberculosis and pneumococcal pneumonia. In parallel, we discuss the interactions of alcohol and HIV on the risk for acute lung injury and subsequent morbidity and mortality. We then discuss the pathophysiology of how these two diseases of immune dysfunction affect the lung, with a focus on the oxidative stress, alveolar macrophage host immune capacity, and immunomodulatory role of zinc in the airway. Finally, we review the latest literature on how HIV and alcohol affect other pulmonary disorders including chronic obstructive pulmonary disease, pulmonary hypertension, and lung cancer.

Alcohol-Mediated Zinc Deficiency Within the Alveolar Space: A Potential Fundamental Mechanism Underlying Oxidative Stress and Cellular Dysfunction in the Alcoholic Lung

Zinc is one of the most abundant trace elements in the human body, and its presence is essential for numerous biological processes including enzymatic activity, immune function, protein synthesis, and wound healing. Given these important roles, zinc has a sophisticated transport system to regulate its homeostasis. Determination of zinc status, however, is difficult to determine as serum levels are closely maintained and are not an accurate reflection of total body zinc or metabolism at the organ level. Fortunately, the discovery of zinc-specific fluorescent dyes has allowed for a much better assessment of zinc status in the respiratory system and has revealed that alcoholism perturbs this highly developed zinc metabolism such that its distribution to the lung and alveolar space is significantly decreased. As a result, this pulmonary zinc deficiency impairs function in the alveolar macrophage, which is the primary host immune cell within the lower airway. Experimental models have demonstrated that correction of this zinc deficiency restores immune function to the alveolar macrophage as best reflected by improved bacterial clearance in response to infection. While the precise mechanisms underlying alcohol-induced zinc deficiency are still under investigation, there is experimental evidence of several important connections with granulocyte–macrophage colony-stimulating factor and oxidative stress, suggesting that alteration of zinc homeostasis may be a fundamental mechanism underlying the cellular pathology seen in the alcohol lung phenotype. This chapter reviews zinc homeostasis and offers insight into our understanding of zinc deficiency in the setting of alcoholism and the potential of zinc as a therapeutic modality in the vulnerable alcoholic host.

Activating the Nrf2-mediated antioxidant response element restores barrier function in the alveolar epithelium of HIV-1 transgenic rats

The master transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2) regulates the expression of antioxidant and phase II-metabolizing enzymes by activating the antioxidant response element (ARE) and thereby protects cells and tissues from oxidative stress. Pulmonary complications remain the leading cause of death in human immunodeficiency virus (HIV)-1-infected individuals, who display systemic oxidative stress and glutathione deficiency that can be modeled in transgenic rats where HIV-1-related viral proteins decrease glutathione levels and cause epithelial barrier dysfunction within the alveolar space by as yet unknown mechanisms. We hypothesized that HIV-1-related proteins inhibit Nrf2-mediated antioxidant defenses and thereby disrupt the normally tight alveolar epithelial barrier. Nrf2 RNA silencing dampened Nrf2/ARE activity, decreased the expression of the tight junction proteins zonula occludens-1, occludin, and claudin-18, increased paracellular permeability of alveolar epithelial monolayers derived from wild-type rats, and therefore reproduced the effects of HIV-1 transgene expression on the epithelial barrier that we had previously described. In contrast, upregulating Nrf2 activity, either by plasmid-mediated overexpression or treatment with the Nrf2 activator sulforaphane, increased the expression of ARE-dependent antioxidants, including NAD(P)H dehydrogenase, quinone 1 and glutathione, improved the expression of tight junction proteins, and restored the ability to form tight barriers in alveolar epithelial cells from HIV-1 transgenic rats. Taken together, these new findings argue that HIV-1-related proteins downregulate Nrf2 expression and/or activity within the alveolar epithelium, which in turn impairs antioxidant defenses and barrier function, thereby rendering the lung susceptible to oxidative stress and injury. Furthermore, this study suggests that activating the Nrf2/ARE pathway with the dietary supplement sulforaphane could augment antioxidant defenses and lung health in HIV-1-infected individuals.

Human immunodeficiency virus-1 transgene expression increases pulmonary vascular resistance and exacerbates hypoxia-induced pulmonary hypertension development

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by increased pulmonary arterial resistance and vessel remodeling. Patients living with human immunodeficiency virus-1 (HIV-1) have an increased susceptibility to develop severe pulmonary hypertension (PH) irrespective of their CD4+ lymphocyte counts. While the underlying cause of HIV-PAH remains unknown, the interaction of HIV-1 proteins with the vascular endothelium may play a critical role in HIV-PAH development. Hypoxia promotes PH in experimental models and in humans, but the impact of HIV-1 proteins on hypoxia-induced pulmonary vascular dysfunction and PAH has not been examined. Therefore, we hypothesize that the presence of HIV-1 proteins and hypoxia synergistically augment the development of pulmonary vascular dysfunction and PH. We examined the effect of HIV-1 proteins on pulmonary vascular resistance by measuring pressure-volume relationships in isolated lungs from wild-type (WT) and HIV-1 Transgenic (Tg) rats. WT and HIV-1 Tg rats were exposed to 10% O₂ for four weeks to induce experimental pulmonary hypertension to assess whether HIV-1 protein expression would impact the development of hypoxia-induced PH. Our results demonstrate that HIV-1 protein expression significantly increased pulmonary vascular resistance (PVR). HIV-1 Tg mice demonstrated exaggerated pulmonary vascular responses to hypoxia as evidenced by greater increases in right ventricular systolic pressures, right ventricular hypertrophy and vessel muscularization when compared to wild-type controls. This enhanced PH was associated with enhanced expression of HIF-1α and PCNA. In addition, in vitro studies reveal that medium from HIV-infected monocyte derived macrophages (MDM) potentiates hypoxia-induced pulmonary artery endothelial proliferation. These results indicate that the presence of HIV-1 proteins likely impact pulmonary vascular resistance and exacerbate hypoxia-induced PH.

Alcohol ingestion disrupts alveolar epithelial barrier function by activation of macrophage-derived transforming growth factor beta1

Background

Chronic alcohol abuse causes oxidative stress and impairs alveolar epithelial barrier integrity, thereby rendering the lung susceptible to acute edematous injury. Experimentally, alcohol-induced oxidative stress increases the expression of transforming growth factor β1 (TGFβ1) in the lung; however, we do not know the precise contribution of various alveolar cells in this process. In the present study, we focused on cell-cell interactions between alveolar macrophages and epithelial cells and the potential mechanisms by which TGFβ1 may become activated in the alveolar space of the alcoholic lung.

Methods

Primary alveolar macrophages and epithelial cells were isolated from control- and alcohol-fed Sprague–Dawley rats. Expression of TGFβ1 and the epithelial integrin αvβ6 were examined by real time PCR and either immunocytochemistry or flow cytometry. Alveolar epithelial cells were cultured on transwell supports in the presence of macrophage cell lysate from control- or alcohol-fed rats or in the presence of viable macrophages ± alcohol. Epithelial barrier function was assessed by transepithelial resistance (TER) and paracellular flux of Texas Red dextran.

Results

TGFβ1 expression was increased in alveolar macrophages from alcohol-fed rats, and TGFβ1 protein was predominantly membrane-bound. Importantly, alveolar macrophage cellular lysate from alcohol-fed rats decreased TER and increased paracellular dextran flux in primary alveolar epithelial cell monolayers as compared to the lysates from control-fed rats. Alcohol-induced epithelial barrier dysfunction was prevented by anti-TGFβ1 antibody treatment, indicating the presence of bioactive TGFβ1 in the macrophage lysate. In addition, co-culturing macrophages and epithelial cells in the presence of alcohol decreased epithelial barrier function, which also was prevented by anti-TGFβ1 and anti-αvβ6 treatment. In parallel, chronic alcohol ingestion in vivo, or direct treatment with active TGFβ1 in vitro, increased the expression of αvβ6 integrin, which is known to activate TGFβ1, in alveolar epithelial cells.

Conclusions

Taken together, these data suggest that interactions between alveolar epithelial cells and macrophages contribute to the alcohol-mediated disruption of epithelial barrier function via the expression and activation of TGFβ1 at points of cell-cell contact.

Adolescent HIV-1 transgenic rats: evidence for dopaminergic alterations in behavior and neurochemistry revealed by methamphetamine challenge

Since the introduction of combination antiretroviral therapy (cART) in the mid-90s, the most severe forms of HIV-1-associated neurocognitive disorders (HAND) have diminished. However, milder forms of HAND remain prevalent. Basic and clinical studies implicate alterations in the dopaminergic (DAergic) system in HIV-1 infection. We used the Fischer 344 HIV-1 transgenic (HIV-1 Tg) rat, which expresses 7 of the 9 HIV-1 genes, to examine potential DAergic alterations. Animals were studied beginning at 35 days of age to assess early-onset DAergic alterations, well before any documented neurological symptoms or clinical signs of "wasting". At 48 hr intervals, animals were administered a single dose of methamphetamine (METH) (0, 0.5, 1, 2.5 and 5 mg/kg/ml s.c.) and tested for the auditory startle response (ASR) and prepulse inhibition (PPI), using an auditory prepulse [85 dB(A) broad-band noise stimulus] and an auditory startle stimulus [100 dB(A) broad-band noise stimulus] in a sound-attenuating chamber with a continuous 70 dB(A) white noise background. The protocol used a 5-min acclimation period, 6 startle trials, and 36 PPI trials [ISIs of 0, 8, 40, 80, 120, and 4000 ms, 6-trial blocks, Latin square design]. As the dose of METH increased, PPI of the startle response decreased. The HIV-1 Tg rats displayed a greater dose-dependency to the METH-induced disruption of PPI compared to non-transgenic controls. Western blot analysis of midbrain extracts revealed lower tyrosine hydroxylase (TH) protein levels and higher monoamine oxidase A (MAO-A) protein levels in HIV-1 Tg rats treated with METH compared to non-transgenic controls. Early-detected cognitive alterations in the preattentive process of sensorimotor gating may have significant predictive utility regarding the progression of DAergic alterations in HIV-1 infection.

Endotoxin-induced cytokine and chemokine expression in the HIV-1 transgenic rat

Background

Repeated exposure to a low dose of a bacterial endotoxin such as lipopolysaccharide (LPS) causes immune cells to become refractory to a subsequent endotoxin challenge, a phenomenon known as endotoxin tolerance (ET). During ET, there is an imbalance in pro- and anti-inflammatory cytokine and chemokine production, leading to a dysregulated immune response. HIV-1 viral proteins are known to have an adverse effect on the immune system. However, the effects of HIV-1 viral proteins during ET have not been investigated.

Methods

In this study, HIV-1 transgenic (HIV-1Tg) rats and control F344 rats (n = 12 ea) were randomly treated with 2 non-pyrogenic doses of LPS (LL) to induce ET, or saline (SS), followed by a high challenge dose of LPS (LL+L, SS+L) or saline (LL+S, SS+S). The gene expression of 84 cytokines, chemokines, and their receptors in the brain and spleen was examined by relative quantitative PCR using a PCR array, and protein levels in the brain, spleen, and serum of 7 of these 84 genes was determined using an electrochemiluminescent assay.

Results

In the spleen, there was an increase in key pro-inflammatory (IL1α, IL-1β, IFN-γ) and anti-inflammatory (IL-10) cytokines, and inflammatory chemokines (Ccl2, Ccl7, and Ccl9,) in response to LPS in the SS+L and LL+L (ET) groups of both the HIV-1Tg and F344 rats, but was greater in the HIV-1Tg rats than in the F344. In the ET HIV-1Tg and F344 (LL+L) rats in the spleen, the LPS-induced increase in pro-inflammatory cytokines was diminished and that of the anti-inflammatory cytokine was enhanced compared to the SS+L group rats. In the brain, IL-1β, as well as the Ccl2, Ccl3, and Ccl7 chemokines were increased to a greater extent in the HIV-1Tg rats compared to the F344; whereas Cxcl1, Cxcl10, and Cxcl11 were increased to a greater extent in the F344 rats compared to the HIV-1Tg rats in the LL+L and SS+L groups.

Conclusion

Our data indicate that the continuous presence of HIV-1 viral proteins can have tissue-dependent effects on endotoxin-induced cytokine and chemokine expression in the ET state.

HIV-1 transgene expression in rats induces differential expression of tumor necrosis factor alpha and zinc transporters in the liver and the lung

BACKGROUND

Highly effective antiviral treatment can suppress HIV-1 infection, but the chronic effects of HIV-1-related viral proteins, including gp120 and Tat, on organs such as the lungs can be damaging. HIV-1 transgenic rodent models are useful for studying the systemic effects of these proteins independently of viral infection. We have previously shown that HIV-1 transgene expression (and therefore, HIV-1-related protein expression) in rats decreases alveolar macrophage zinc levels and phagocytic capacity by unknown mechanisms. We hypothesized that HIV-1 transgene expression induces chronic inflammation and zinc sequestration within the liver and thereby decreases zinc bioavailability in the lung. We examined the expression of the pro-inflammatory cytokine, tumor necrosis factor alpha (TNFα), the zinc storage protein, metallothionein (MT1), and the zinc exporter, ZNT1 in the livers and the lungs of wild type and HIV-1 transgenic rats ± dietary zinc supplementation. In addition, we measured zinc levels, the zinc importing protein ZIP1, and the phagocytic capacity in the alveolar macrophages.

RESULTS

HIV-1 transgene expression increased the liver-specific expression of TNFα, suggesting a chronic inflammatory response within the liver in response to HIV-1-related protein expression. In parallel, HIV-1 transgene expression significantly increased MT1 and ZNT1 expression in the liver as compared to the lung, a pattern that is consistent with zinc sequestration in the liver as occurs during systemic inflammation. Further, HIV-1 transgene expression decreased intracellular zinc levels and increased expression of ZIP1 in the alveolar macrophages, a pattern consistent with zinc deficiency, and decreased their bacterial phagocytic capacity. Interestingly, dietary zinc supplementation in HIV-1 transgenic rats decreased gene expression of TNFα, MT1, and ZNT1 in the liver while simultaneously increasing their expression in the lung. In parallel, zinc supplementation increased alveolar macrophage intracellular zinc levels and bacterial phagocytic capacity in HIV-1 transgenic rats.

CONCLUSION

Taken together, these findings suggest that chronic HIV-1-related protein expression causes liver inflammation and zinc sequestration, which in turn limits zinc bioavailability in the lung and thereby impairs alveolar macrophage phagocytic function. Importantly, dietary zinc supplementation decreases liver inflammation and zinc sequestration and restores alveolar macrophage phagocytic function in HIV-1 transgenic rats, a result with potential clinical implications for improving lung health in HIV-1-infected individuals.

Chronic alcohol ingestion exacerbates lung epithelial barrier dysfunction in HIV-1 transgenic rats

BACKGROUND

Alcohol abuse and HIV-1 infection frequently coexist, and these individuals are at high risk for serious lung infections and respiratory failure. Although alcohol ingestion and HIV-1 transgene expression have been shown to independently cause oxidative stress and disrupt alveolar epithelial barrier function in experimental models, their interactive effects have not been examined.

METHODS AND RESULTS

In this study, we determined that chronic alcohol ingestion (12 weeks) exacerbated the already significant defects in alveolar epithelial paracellular permeability and lung liquid clearance in HIV-1 transgenic rats. Further, immunocytochemical analyses of tight junction protein expression in primary alveolar epithelial cells showed that occludin and zonula occludens-1 localization within the plasma membrane was more disrupted than in either condition alone, consistent with the observed defects in epithelial barrier function. Interestingly, expression of nuclear factor-erythroid 2-related factor 2 (Nrf2), the transcription factor required to activate the antioxidant-response element, was decreased in primary alveolar epithelial cells isolated from HIV-1 transgenic rats. In parallel, exposing lung epithelial cells in vitro to either alcohol or the HIV-related protein gp120 also decreased Nrf2 expression. Importantly, treatment with procysteine, which increases thiol antioxidants including glutathione, improved tight junction protein localization in the plasma membrane and restored alveolar epithelial barrier function in alcohol-fed HIV-1 transgenic rats.

CONCLUSIONS

These results provide novel evidence that HIV-related proteins and alcohol together causes more barrier dysfunction in the lung epithelium than either stress alone. However, these significant effects on the alveolar barrier can be mitigated by augmenting the thiol antioxidant pool, a strategy with potential clinical applications in subjects who are highly vulnerable to lung disease because of coexistent alcohol abuse and HIV infection.

Focus on the lung

Both HIV-1 infection and chronic alcohol abuse adversely affect lung health. For example, through multiple mechanisms, chronic alcohol abuse increases one's susceptibility to pneumonia, particularly pneumonia caused by certain serious pathogens. Similarly, pneumonia caused by opportunistic pathogens is very common in HIV-infected patients, at least in part because HIV-1 attacks the immune cells of the lungs and interferes with their functions. Alcohol abuse also increases the risk of developing acute respiratory distress syndrome, a serious acute lung condition; however, the association of this syndrome with HIV-1 infection remains unclear. Chronic lung conditions potentially caused or exacerbated by chronic alcohol abuse include asthma, emphysema, or chronic bronchitis, although the findings to date are equivocal. However, growing evidence indicates that HIV-1 infection increases the risk of chronic pulmonary diseases such as emphysema, lung cancer, and excessive blood pressure in the vessels supplying the lung (i.e., pulmonary hypertension). Both alcohol abuse and HIV infection can impair lung function through various mechanisms, including increasing oxidative stress and enhancing antioxidant deficits, preventing full activation of the lung's immune cells, and contributing to zinc deficiency. However, the interactions between alcohol abuse and HIV-1 infection in contributing to the range of lung disorders have not been studied in detail.

HIV-1 transgene expression in rats causes oxidant stress and alveolar epithelial barrier dysfunction

Background

HIV-infected individuals are at increased risk for acute and chronic airway disease even though there is no evidence that the virus can infect the lung epithelium. Although HIV-related proteins including gp120 and Tat can directly cause oxidant stress and cellular dysfunction, their effects in the lung are unknown. The goal of this study was to determine the effects of HIV-1 transgene expression in rats on alveolar epithelial barrier function. Alveolar epithelial barrier function was assessed by determining lung liquid clearance in vivo and alveolar epithelial monolayer permeability in vitro. Oxidant stress in the alveolar space was determined by measuring the glutathione redox couple by high performance liquid chromatography, and the expression and membrane localization of key tight junction proteins were assessed. Finally, the direct effects of the HIV-related proteins gp120 and Tat on alveolar epithelial barrier formation and tight junction protein expression were determined.

Results

HIV-1 transgene expression caused oxidant stress within the alveolar space and impaired epithelial barrier function even though there was no evidence of overt inflammation within the airways. The expression and membrane localization of the tight junction proteins zonula occludens-1 and occludin were decreased in alveolar epithelial cells from HIV-1 transgenic rats. Further, treating alveolar epithelial monolayers from wild type rats in vitro with recombinant gp120 or Tat for 24 hours reproduced many of the effects on zonula occludens-1 and occludin expression and membrane localization.

Conclusion

Taken together, these data indicate that HIV-related proteins cause oxidant stress and alter the expression of critical tight junction proteins in the alveolar epithelium, resulting in barrier dysfunction.

Zinc deficiency mediates alcohol-induced alveolar epithelial and macrophage dysfunction in rats

Chronic alcohol abuse impairs both alveolar epithelial and macrophage function, and renders individuals susceptible to acute lung injury, pneumonia, and other serious lung diseases. Zinc deficiency, which is known to impact both epithelial and immune cell functions, is also associated with alcohol abuse. In this study, chronic alcohol ingestion (6 wk) in rats altered expression of key zinc transporters and storage proteins in the small intestine and the lung, and decreased zinc levels in the alveolar compartment. Zinc supplementation of alveolar epithelial monolayers derived from alcohol-fed rats in vitro, or of the diets of alcohol-fed rats in vivo, restored alveolar epithelial barrier function, and these improvements were associated with salutary changes in tight junction protein expression and membrane localization. In parallel, dietary zinc supplementation increased intracellular zinc levels, GM-CSF receptor expression, and bacterial phagocytic capacity in the alveolar macrophages of alcohol-fed rats. Together, these studies implicate zinc deficiency as a novel mechanism mediating alcohol-induced alveolar epithelial and macrophage dysfunction. Importantly, these findings argue that dietary supplementation can overcome alcohol-induced zinc deficiency and restore alveolar epithelial and macrophage function, and therefore could be an effective treatment for the susceptible alcoholic lung phenotype.

Biomarkers of HIV Immune Reconstitution Inflammatory Syndrome

Dysregulation of the immune system drives HIV pathogenesis. As we develop new ways to treat HIV and AIDS, we encounter new clinical ramifications of our treatment on regulatory components of the immune system. HIV-associated Immune Reconstitution Inflammatory Syndrome (IRIS) occurs after initiation of anti-retroviral therapy (ART) with inappropriate and dysbalanced restoration of the immune system resulting in pathologic inflammatory reactions with significant morbidity. IRIS is most commonly associated with latent, occult, or past infections, including tuberculosis, Cryptococcus neoformans, and Mycobacterium avium-complex. We discuss common clinical presentations, new diagnostic modalities, current hypotheses of IRIS pathogenesis, and future directions of IRIS-related research, focusing on the identification of biomarkers that can be used to predict and diagnose IRIS.