Effect of HIV-1-related protein expression on cardiac and skeletal muscles from transgenic rats

The Preventive Effect of Specific Collagen Peptides against Dexamethasone-Induced Muscle Atrophy in Mice

Muscle atrophy, also known as muscle wasting, is the thinning of muscle mass due to muscle disuse, aging, or diseases such as cancer or neurological problems. Muscle atrophy is closely related to the quality of life and has high morbidity and mortality. However, therapeutic options for muscle atrophy are limited, so studies to develop therapeutic agents for muscle loss are always required. For this study, we investigated how orally administered specific collagen peptides (CP) affect muscle atrophy and elucidated its molecular mechanism using an in vivo model. We treated mice with dexamethasone (DEX) to induce a muscular atrophy phenotype and then administered CP (0.25 and 0.5 g/kg) for four weeks. In a microcomputed tomography analysis, CP (0.5 g/kg) intake significantly increased the volume of calf muscles in mice with DEX-induced muscle atrophy. In addition, the administration of CP (0.25 and 0.5 g/kg) restored the weight of the gluteus maximus and the fiber cross-sectional area (CSA) of the pectoralis major and calf muscles, which were reduced by DEX. CP significantly inhibited the mRNA expression of myostatin and the phosphorylation of Smad2, but it did not affect TGF-β, BDNF, or FNDC5 gene expression. In addition, AKT/mTOR, a central pathway for muscle protein synthesis and related to myostatin signaling, was enhanced in the groups that were administered CP. Finally, CP decreased serum albumin levels and increased TNF-α gene expression. Collectively, our in vivo results demonstrate that CP can alleviate muscle wasting through a multitude of mechanisms. Therefore, we propose CP as a supplement or treatment to prevent muscle atrophy.

Evaluation of HIV-Related Cardiomyopathy in HIV-Positive Patients in Bushehr, Iran

Objectives

In 2020, according to the UNAIDS (Joint United Nations Programme on HIV/AIDS), more than 37 million people lived with human immunodeficiency virus (HIV) infection worldwide. The disease is known to affect several organs, and one of the most affected organs is the heart. Cardiac diseases are highly prevalent among HIV-infected individuals, and recent findings suggest that this could be due to the damage caused by the virus. HIV patients are subject to advanced immunosuppression, which may lead to cardiac muscle damage and, in turn, cardiomyopathy. We aimed to study the incidence of HIV-related cardiomyopathy.

Methods

A pilot cross-sectional study was conducted to assess cardiomyopathy among 200 HIV patients who presented to the Heart Center, Bushehr, Iran. Patients’ files were used to determine the demographic data including age, gender, education, marital status, history of illicit drug use, unsafe/unprotected sexual contact, and whether the patient was a prisoner. Several laboratory data were also collected from these files. Physical examination of the cardiovascular system and echocardiography were also included as part of the evaluation.

Results

Although at least four out of five patients presented with some kind of cardiac damage, including valvular damage and pericardial effusion, none was diagnosed with cardiomyopathy. Valvular dysfunction was detected in 88.5% of the patients. Diastolic dysfunction was found in 7.7% of them. The mean ejection fraction was found to be 58%. In addition to cardiomyopathy, none of the patients developed systolic dysfunction, wall motion abnormality, intra-cardiac mass, or vegetation.

Conclusions

Cardiovascular complications are common among HIV-infected patients. Cardiomyopathy was not detected in our patients. In addition, the most common manifestations that were detected among our patients were valvular heart diseases and pericardial effusion.

A Link Between Methylglyoxal and Heart Failure During HIV-1 Infection

Early-onset heart failure (HF) continues to be a major cause of morbidity and mortality in people living with human immunodeficiency virus type one (HIV-1) infection (PLWH), yet the molecular causes for this remain poorly understood. Herein NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ humanized mice (Hu-mice), plasma from PLWH, and autopsied cardiac tissues from deceased HIV seropositive individuals were used to assess if there is a link between the glycolysis byproduct methylglyoxal (MG) and HF in the setting of HIV-1 infection. At five weeks post HIV infection, Hu-mice developed grade III-IV diastolic dysfunction (DD) with an associated two-fold increase in plasma MG. At sixteen-seventeen weeks post infection, cardiac ejection fraction and fractional shortening also declined by 26 and 35%, and plasma MG increased to four-fold higher than uninfected controls. Histopathological and biochemical analyses of cardiac tissues from Hu-mice 17 weeks post-infection affirmed MG increase with a concomitant decrease in expression of the MG-degrading enzyme glyoxalase-1 (Glo1). The endothelial cell marker CD31 was found to be lower, and coronary microvascular leakage and myocardial fibrosis were prominent. Increasing expression of Glo1 in Hu-mice five weeks post-infection using a single dose of an engineered AAV2/9 (1.7 × 10¹² virion particles/kg), attenuated the increases in plasma and cardiac MG levels. Increasing Glo1 also blunted microvascular leakage, fibrosis, and HF seen at sixteen weeks post-infection, without changes in plasma viral loads. In plasma from virally suppressed PLWH, MG was also 3.7-fold higher. In autopsied cardiac tissues from seropositive, HIV individuals with low viral log, MG was 4.2-fold higher and Glo1 was 50% lower compared to uninfected controls. These data show for the first time a causal link between accumulation of MG and HF in the setting of HIV infection.

HIV-1-Associated Left Ventricular Cardiac Dysfunction in Humanized Mice

The molecular cause(s) for early onset heart failure in people living with HIV-1 infection (PLWH) remains poorly defined. Herein, longitudinal echocardiography was used to assess whether NOD.Cg-Prkdc^scid Il2rgt^m1Wjl/SzJ mice reconstituted with human hematopoietic stem cells (Hu-NSG mice) and infected with HIV-1_ADA can recapitulate the salient features of this progressive human disease. Four weeks post infection, Hu-NSG mice of both sexes developed left ventricular (LV) diastolic dysfunction (DD), with 25% exhibiting grade III/IV restrictive DD with mitral regurgitation. Increases in global longitudinal and circumferential strains and declines in LV ejection fraction and fractional shortening were observed eight weeks post infection. After twelve weeks of infection, 33% of Hu-NSG mice exhibited LV dyskinesia and dyssynchrony. Histopathological analyses of hearts seventeen weeks post infection revealed coronary microvascular leakage, fibrosis and immune cell infiltration into the myocardium. These data show for the first time that HIV-1_ADA-infected Hu-NSG mice can recapitulate key left ventricular cardiac deficits and pathophysiological changes reported in humans with progressive HIV-1 infection. The results also suggest that HIV-1 infected Hu-NSG mice may be a useful model to screen for pharmacological agents to blunt LV dysfunction and associated pathophysiologic causes reported in PLWH.

Skeletal muscle atrogenes: From rodent models to human pathologies

Skeletal muscle atrophy is a common side effect of most human diseases. Muscle loss is not only detrimental for the quality of life but it also dramatically impairs physiological processes of the organism and decreases the efficiency of medical treatments. While hypothesized for years, the existence of an atrophying programme common to all pathologies is still incompletely solved despite the discovery of several actors and key regulators of muscle atrophy. More than a decade ago, the discovery of a set of genes, whose expression at the mRNA levels were similarly altered in different catabolic situations, opened the way of a new concept: the presence of atrogenes, i.e. atrophy-related genes. Importantly, the atrogenes are referred as such on the basis of their mRNA content in atrophying muscles, the regulation at the protein level being sometimes more complicate to elucidate. It should be noticed that the atrogenes are markers of atrophy and that their implication as active inducers of atrophy is still an open question for most of them. While the atrogene family has grown over the years, it has mostly been incremented based on data coming from rodent models. Whether the rodent atrogenes are valid for humans still remain to be established. An "atrogene" was originally defined as a gene systematically up- or down-regulated in several catabolic situations. Even if recent works often restrict this notion to the up-regulation of a limited number of proteolytic enzymes, it is important to keep in mind the big picture view. In this review, we provide an update of the validated and potential rodent atrogenes and the metabolic pathways they belong, and based on recent work, their relevance in human physio-pathological situations. We also propose a more precise definition of the atrogenes that integrates rapid recovery when catabolic stimuli are stopped or replaced by anabolic ones.

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.

Combination ART-Induced Oxidative/Nitrosative Stress, Neurogenic Inflammation and Cardiac Dysfunction in HIV-1 Transgenic (Tg) Rats: Protection by Mg

Chronic effects of a combination antiretroviral therapy (cART = tenofovir/emtricitatine + atazanavir/ritonavir) on systemic and cardiac oxidative stress/injury in HIV-1 transgenic (Tg) rats and protection by Mg-supplementation were assessed. cART (low doses) elicited no significant effects in normal rats, but induced time-dependent oxidative/nitrosative stresses: 2.64-fold increased plasma 8-isoprostane, 2.0-fold higher RBC oxidized glutathione (GSSG), 3.2-fold increased plasma 3-nitrotyrosine (NT), and 3-fold elevated basal neutrophil superoxide activity in Tg rats. Increased NT staining occurred within cART-treated HIV-Tg hearts, and significant decreases in cardiac systolic and diastolic contractile function occurred at 12 and 18 weeks. HIV-1 expression alone caused modest levels of oxidative stress and cardiac dysfunction. Significantly, cART caused up to 24% decreases in circulating Mg in HIV-1-Tg rats, associated with elevated renal NT staining, increased creatinine and urea levels, and elevated plasma substance P levels. Strikingly, Mg-supplementation (6-fold) suppressed all oxidative/nitrosative stress indices in the blood, heart and kidney and substantially attenuated contractile dysfunction (>75%) of cART-treated Tg rats. In conclusion, cART caused significant renal and cardiac oxidative/nitrosative stress/injury in Tg-rats, leading to renal Mg wasting and hypomagnesemia, triggering substance P-dependent neurogenic inflammation and cardiac dysfunction. These events were effectively attenuated by Mg-supplementation likely due to its substance P-suppressing and Mg’s intrinsic anti-peroxidative/anti-calcium properties.

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.

Neuroinflammation and Behavior in HIV-1 Transgenic Rats Exposed to Chronic Adolescent Stress

Highly active antiretroviral therapy (HAART) has improved prognosis for people living with HIV (PLWH) and dramatically reduced the incidence of AIDS. However, even when viral load is controlled, PLWH develop psychiatric and neurological disorders more frequently than those living without HIV. Adolescents with HIV are particularly susceptible to the development of psychiatric illnesses and neurocognitive impairments. While both psychiatric and neurocognitive disorders have been found to be exacerbated by stress, the extent to which chronic stress and HIV-1 viral proteins interact to impact behavior and relevant neuroinflammatory processes is unknown. Determination of the individual contributions of stress and HIV to neuropsychiatric disorders is heavily confounded in humans. In order to isolate the influence of HIV-1 proteins and chronic stress on behavior and neuroinflammation, we employed the HIV-1 transgenic (Tg) rat model, which expresses HIV-1 proteins with a gag and pol deletion, allowing for viral protein expression without viral replication. This Tg line has been characterized as a model of HAART-controlled HIV-1 infection due to the lack of viral replication but continued presence of HIV-1 proteins. We exposed male and female adolescent HIV-1 Tg rats to a mixed-modality chronic stress paradigm consisting of isolation, social defeat and restraint, and assessed behavior, cerebral vascularization, and neuroinflammatory endpoints. Stress, sex, and presence of the HIV-1 transgene impacted weight gain in adolescent rats. Female HIV-1 Tg rats showed decreases in central tendency during the light cycle in the open field regardless of stress exposure. Both male and female HIV-1 Tg rats exhibited decreased investigative behavior in the novel object recognition task, but no memory impairments. Adolescent stress had no effect on the tested behaviors. Microglia in female HIV-1 Tg rats exhibited a hyper-ramified structure, and gene expression of complement factor B was increased in the hippocampus. In addition, adolescent stress exposure increased microglial branching and junctions in female wild-type rats without causing any additional increase in HIV-1 rats. These data suggest that the presence of HIV-1 proteins during development leads to alterations in behavioral and neuroinflammatory endpoints that are not further impacted by concurrent chronic adolescent stress.

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.

Heme oxygenase-1 dysregulation in the brain: implications for HIV-associated neurocognitive disorders

Heme oxygenase-1 (HO-1) is a highly inducible and ubiquitous cellular enzyme that subserves cytoprotective responses to toxic insults, including inflammation and oxidative stress. In neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and multiple sclerosis, HO-1 expression is increased, presumably reflecting an endogenous neuroprotective response against ongoing cellular injury. In contrast, we have found that in human immunodeficiency virus (HIV) infection of the brain, which is also associated with inflammation, oxidative stress and neurodegeneration, HO-1 expression is decreased, likely reflecting a unique role for HO-1 deficiency in neurodegeneration pathways activated by HIV infection. We have also shown that HO-1 expression is significantly suppressed by HIV replication in cultured macrophages which represent the primary cellular reservoir for HIV in the brain. HO-1 deficiency is associated with release of neurotoxic levels of glutamate from both HIV-infected and immune-activated macrophages; this glutamate-mediated neurotoxicity is suppressed by pharmacological induction of HO-1 expression in the macrophages. Thus, HO-1 induction could be a therapeutic strategy for neuroprotection against HIV infection and other neuroinflammatory brain diseases. Here, we review various stimuli and signaling pathways regulating HO-1 expression in macrophages, which could promote neuronal survival through HO-1-modulation of endogenous antioxidant and immune modulatory pathways, thus limiting the oxidative stress that can promote HIV disease progression in the CNS. The use of pharmacological inducers of endogenous HO-1 expression as potential adjunctive neuroprotective therapeutics in HIV infection is also discussed.

Skeletal muscle atrophy and the E3 ubiquitin ligases MuRF1 and MAFbx/atrogin-1

Muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx)/atrogin-1 were identified more than 10 years ago as two muscle-specific E3 ubiquitin ligases that are increased transcriptionally in skeletal muscle under atrophy-inducing conditions, making them excellent markers of muscle atrophy. In the past 10 years much has been published about MuRF1 and MAFbx with respect to their mRNA expression patterns under atrophy-inducing conditions, their transcriptional regulation, and their putative substrates. However, much remains to be learned about the physiological role of both genes in the regulation of mass and other cellular functions in striated muscle. Although both MuRF1 and MAFbx are enriched in skeletal, cardiac, and smooth muscle, this review will focus on the current understanding of MuRF1 and MAFbx in skeletal muscle, highlighting the critical questions that remain to be answered.

Pro-inflammatory mediation of myoblast proliferation

Skeletal muscle satellite cell function is largely dictated by the surrounding environment following injury. Immune cell infiltration dominates the extracellular space in the injured area, resulting in increased cytokine concentrations. While increased pro-inflammatory cytokine expression has been previously established in the first 3 days following injury, less is known about the time course of cytokine expression and the specific mechanisms of cytokine induced myoblast function. Therefore, the expression of IL-1β and IL-6 at several time points following injury, and their effects on myoblast proliferation, were examined. In order to do this, skeletal muscle was injured using barium chloride in mice and tissue was collected 1, 5, 10, and 28 days following injury. Mechanisms of cytokine induced proliferation were determined in cell culture using both primary and C2C12 myoblasts. It was found that there is a ∼20-fold increase in IL-1β (p≤0.05) and IL-6 (p = 0.06) expression 5 days following injury. IL-1β increased proliferation of both primary and C2C12 cells ∼25%. IL-1β stimulation also resulted in increased NF-κB activity, likely contributing to the increased proliferation. These data demonstrate for the first time that IL-1β alone can increase the mitogenic activity of primary skeletal muscle satellite cells and offer insight into the mechanisms dictating satellite cell function following injury.

HIV protease inhibitors and onset of cardiovascular diseases: a central role for oxidative stress and dysregulation of the ubiquitin-proteasome system

The successful roll-out of highly active antiretroviral therapy (HAART) has extended life expectancy and enhanced the overall well-being of HIV-positive individuals. There are, however, increased concerns regarding HAART-mediated metabolic derangements and its potential risk for cardiovascular diseases (CVD) in the long-term. Here certain classes of antiretroviral drugs such as the HIV protease inhibitors (PIs) are strongly implicated in this process. This article largely focuses on the direct PI-linked development of cardio-metabolic complications, and reviews the inter-linked roles of oxidative stress and the ubiquitin-proteasome system (UPS) as key mediators driving this process. It is proposed that PIs trigger reactive oxygen species (ROS) production that leads to serious downstream consequences such as cell death, impaired mitochondrial function, and UPS dysregulation. Moreover, we advocate that HIV PIs may also directly lower myocardial UPS function. The attenuation of cardiac UPS can initiate transcriptional changes that contribute to perturbed lipid metabolism, thereby fueling a pro-atherogenic milieu. It may also directly alter ionic channels and interfere with electrical signaling in the myocardium. Therefore HIV PI-induced ROS together with a dysfunctional UPS elicit detrimental effects on the cardiovascular system that will eventually result in the onset of heart diseases. Thus while HIV PIs substantially improve life expectancy and quality of life in HIV-positive patients, its longer-term side-effects on the cardiovascular system should lead to a) greater clinical awareness regarding its benefit-harm paradigm, and b) the development and evaluation of novel co-treatment strategies.

Chronic alcohol ingestion delays skeletal muscle regeneration following injury

Background

Chronic alcohol ingestion may cause severe biochemical and pathophysiological derangements to skeletal muscle. Unfortunately, these alcohol-induced events may also prime skeletal muscle for worsened, delayed, or possibly incomplete repair following acute injury. As alcoholics may be at increased risk for skeletal muscle injury, our goals were to identify the effects of chronic alcohol ingestion on components of skeletal muscle regeneration. To accomplish this, age- and gender-matched C57Bl/6 mice were provided normal drinking water or water that contained 20% alcohol (v/v) for 18–20 wk. Subgroups of mice were injected with a 1.2% barium chloride (BaCl₂) solution into the tibialis anterior (TA) muscle to initiate degeneration and regeneration processes. Body weights and voluntary wheel running distances were recorded during the course of recovery. Muscles were harvested at 2, 7 or 14 days post-injection and assessed for markers of inflammation and oxidant stress, fiber cross-sectional areas, levels of growth and fibrotic factors, and fibrosis.

Results

Body weights of injured, alcohol-fed mice were reduced during the first week of recovery. These mice also ran significantly shorter distances over the two weeks following injury compared to uninjured, alcoholics. Injured TA muscles from alcohol-fed mice had increased TNFα and IL6 gene levels compared to controls 2 days after injury. Total protein oxidant stress and alterations to glutathione homeostasis were also evident at 7 and 14 days after injury. Ciliary neurotrophic factor (CNTF) induction was delayed in injured muscles from alcohol-fed mice which may explain, in part, why fiber cross-sectional area failed to normalize 14 days following injury. Gene levels of TGFβ₁ were induced early following injury before normalizing in muscle from alcohol-fed mice compared to controls. However, TGFβ₁ protein content was consistently elevated in injured muscle regardless of diet. Fibrosis was increased in injured, muscle from alcohol-fed mice at 7 and 14 days of recovery compared to injured controls.

Conclusions

Chronic alcohol ingestion appears to delay the normal regenerative response following significant skeletal muscle injury. This is evidenced by reduced cross-sectional areas of regenerated fibers, increased fibrosis, and altered temporal expression of well-described growth and fibrotic factors.

Altered lipid concentrations of liver, heart and plasma but not brain in HIV-1 transgenic rats

Disturbed lipid metabolism has been reported in antiretroviral-naive HIV-1-infected patients suggesting a direct effect of the virus on lipid metabolism. To test that the HIV-1 virus alone could alter lipid concentrations, we measured these concentrations in an HIV-1 transgenic (Tg) rat model of human HIV-1 infection, which demonstrates peripheral and central pathology by 7-9 months of age. Concentrations were measured in high-energy microwaved heart, brain and liver from 7-9 month-old HIV-1 Tg and wildtype rats, and in plasma from non-microwaved rats. Plasma triglycerides and liver cholesteryl ester and total cholesterol concentrations were significantly higher in HIV-1 Tg rats than controls. Heart and plasma fatty acid concentrations reflected concentration differences in liver, which showed higher n-3 and n-6 polyunsaturated fatty acid (PUFA) concentrations in multiple lipid compartments. Fatty acid concentrations were increased or decreased in heart and liver phospholipid subfractions. Brain fatty acid concentrations differed significantly between the groups for minor fatty acids such as linoleic acid and n-3 docosapentaenoic acid. The profound changes in heart, plasma and liver lipid concentrations suggest a direct effect of chronic exposure to the HIV-1 virus on peripheral lipid (including PUFA) metabolism.

Molecular and cellular mechanisms of skeletal muscle atrophy: an update

Skeletal muscle atrophy is defined as a decrease in muscle mass and it occurs when protein degradation exceeds protein synthesis. Potential triggers of muscle wasting are long-term immobilization, malnutrition, severe burns, aging as well as various serious and often chronic diseases, such as chronic heart failure, obstructive lung disease, renal failure, AIDS, sepsis, immune disorders, cancer, and dystrophies. Interestingly, a cooperation between several pathophysiological factors, including inappropriately adapted anabolic (e.g., growth hormone, insulin-like growth factor 1) and catabolic proteins (e.g., tumor necrosis factor alpha, myostatin), may tip the balance towards muscle-specific protein degradation through activation of the proteasomal and autophagic systems or the apoptotic pathway. Based on the current literature, we present an overview of the molecular and cellular mechanisms that contribute to muscle wasting. We also focus on the multifacetted therapeutic approach that is currently employed to prevent the development of muscle wasting and to counteract its progression. This approach includes adequate nutritional support, implementation of exercise training, and possible pharmacological compounds.

Premature expression of a muscle fibrosis axis in chronic HIV infection

Background

Despite the success of highly active antiretroviral therapy (HAART), HIV infected individuals remain at increased risk for frailty and declines in physical function that are more often observed in older uninfected individuals. This may reflect premature or accelerated muscle aging.

Methods

Skeletal muscle gene expression profiles were evaluated in three uninfected independent microarray datasets including young (19 to 29 years old), middle aged (40 to 45 years old) and older (65 to 85 years old) subjects, and a muscle dataset from HIV infected subjects (36 to 51 years old). Using Bayesian analysis, a ten gene muscle aging signature was identified that distinguished young from old uninfected muscle and included the senescence and cell cycle arrest gene p21/Cip1 (CDKN1A). This ten gene signature was then evaluated in muscle specimens from a cohort of middle aged (30 to 55 years old) HIV infected individuals. Expression of p21/Cip1 and related pathways were validated and further analyzed in a rodent model for HIV infection.

Results

We identify and replicate the expression of a set of muscle aging genes that were prematurely expressed in HIV infected, but not uninfected, middle aged subjects. We validated select genes in a rodent model of chronic HIV infection. Because the signature included p21/Cip1, a cell cycle arrest gene previously associated with muscle aging and fibrosis, we explored pathways related to senescence and fibrosis. In addition to p21/Cip1, we observed HIV associated upregulation of the senescence factor p16INK4a (CDKN2A) and fibrosis associated TGFβ1, CTGF, COL1A1 and COL1A2. Fibrosis in muscle tissue was quantified based on collagen deposition and confirmed to be elevated in association with infection status. Fiber type composition was also measured and displayed a significant increase in slow twitch fibers associated with infection.

Conclusions

The expression of genes associated with a muscle aging signature is prematurely upregulated in HIV infection, with a prominent role for fibrotic pathways. Based on these data, therapeutic interventions that promote muscle function and attenuate pro-fibrotic gene expression should be considered in future studies.

Can the vector space model be used to identify biological entity activities?

BACKGROUND

Biological systems are commonly described as networks of entity interactions. Some interactions are already known and integrate the current knowledge in life sciences. Others remain unknown for long periods of time and are frequently discovered by chance. In this work we present a model to predict these unknown interactions from a textual collection using the vector space model (VSM), a well known and established information retrieval model. We have extended the VSM ability to retrieve information using a transitive closure approach. Our objective is to use the VSM to identify the known interactions from the literature and construct a network. Based on interactions established in the network our model applies the transitive closure in order to predict and rank new interactions.

RESULTS

We have tested and validated our model using a collection of patent claims issued from 1976 to 2005. From 266,528 possible interactions in our network, the model identified 1,027 known interactions and predicted 3,195 new interactions. Iterating the model according to patent issue dates, interactions found in a given past year were often confirmed by patent claims not in the collection and issued in more recent years. Most confirmation patent claims were found at the top 100 new interactions obtained from each subnetwork. We have also found papers on the Web which confirm new inferred interactions. For instance, the best new interaction inferred by our model relates the interaction between the adrenaline neurotransmitter and the androgen receptor gene. We have found a paper that reports the partial dependence of the antiapoptotic effect of adrenaline on androgen receptor.

CONCLUSIONS

The VSM extended with a transitive closure approach provides a good way to identify biological interactions from textual collections. Specifically for the context of literature-based discovery, the extended VSM contributes to identify and rank relevant new interactions even if these interactions occur in only a few documents in the collection. Consequently, we have developed an efficient method for extracting and restricting the best potential results to consider as new advances in life sciences, even when indications of these results are not easily observed from a mass of documents.

Chronic alcohol ingestion exacerbates skeletal muscle myopathy in HIV-1 transgenic rats

Background

Separately, chronic alcohol ingestion and HIV-1 infection are associated with severe skeletal muscle derangements, including atrophy and wasting, weakness, and fatigue. One prospective cohort study reported that 41% of HIV-infected patients met the criteria for alcoholism, however; few reports exist on the co-morbid effects of these two disease processes on skeletal muscle homeostasis. Thus, we analyzed the atrophic effects of chronic alcohol ingestion in HIV-1 transgenic rats and identified alterations to several catabolic and anabolic factors.

Findings

Relative plantaris mass, total protein content, and fiber cross-sectional area were reduced in each experimental group compared to healthy, control-fed rats. Alcohol abuse further reduced plantaris fiber area in HIV-1 transgenic rats. Consistent with previous reports, gene levels of myostatin and its receptor activin IIB were not increased in HIV-1 transgenic rat muscle. However, myostatin and activin IIB were induced in healthy and HIV-1 transgenic rats fed alcohol for 12 weeks. Catabolic signaling factors such as TGFβ₁, TNFα, and phospho-p38/total-p38 were increased in all groups compared to controls. There was no effect on IL-6, leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), or ciliary neurotrophic factor (CNTF) in control-fed, transgenic rats. However, the co-morbidity of chronic alcohol abuse and HIV-1-related protein expression decreased expression of the two anabolic factors, CT-1 and CNTF.

Conclusions

Consistent with previous reports, alcohol abuse accentuated skeletal muscle atrophy in an animal model of HIV/AIDS. While some catabolic pathways known to drive alcoholic or HIV-1-associated myopathies were also elevated in this co-morbid model (e.g., TGFβ₁), consistent expression patterns were not apparent. Thus, specific alterations to signaling mechanisms such as the induction of the myostatin/activin IIB system or reductions in growth factor signaling via CT-1- and CNTF-dependent mechanisms may play larger roles in the regulation of muscle mass in alcoholic, HIV-1 models.

Advances in our understanding of the pathogenesis of HIV-1 associated nephropathy in children

Childhood HIV-1 associated nephropathy (HIVAN) is a clinical and renal histological disease characterized by heavy proteinuria associated with focal and segmental glomerular sclerosis and/or mesangial hyperplasia in combination with microcystic tubular dilatation. These lesions lead to renal enlargement and rapid progression to kidney failure. Children of African ancestry have a unique susceptibility to developing HIVAN. It is estimated that approximately 300,000 HIV-infected children living in the sub-Saharan Africa could develop HIVAN if they do not receive appropriate antiretroviral therapy. This article discusses recent developments and controversies related to the pathogenesis of childhood HIVAN. The role of host genetic factors, including the newly identified variants in the APOL1 gene, is discussed in the context of previous studies that established the pathological paradigm for HIVAN, and our current understanding of the functional genomics analysis. Hopefully, these advances will provide new research opportunities to generate better treatments for children with HIVAN.

Limb-girdle muscular dystrophy 2H and the role of TRIM32

Limb-girdle muscular dystrophy (LGMD) 2H is a slowly progressive condition characterized by proximal weakness, atrophy, and mildly to moderately raised levels of creatine kinase. Facial weakness, scapular winging, hypertrophied calves, and Achilles tendon contractions are not uncommon and the age of onset ranges between the first and fourth decade. LGMD2H was originally described in the Hutterite population that resides in central Canada and the Dakotas of the USA. LGMD2H was mapped to a specific mutation in the TRIM32 gene and it has subsequently been shown that the same mutation also results in the "sarcotubular myopathy" syndrome, which was described histopathologically. TRIM32 appears to be an E3 ubiquitin ligase, containing the tripartite motif common to this family of proteins (RING finger, B-box, coiled-coil). A few substrates have been identified, including actin and dysbindin. Recent studies have identified additional mutations in the C-terminal region of TRIM32 that result in a dystrophic myopathy. Although TRIM32 appears to be expressed ubiquitously, it is still not clear why certain mutations of TRIM32 would result in a phenotype relatively restricted to skeletal muscle. A mutation in the B-box region of TRIM32 has also been shown to result in a more pleiotropic disorder, Bardet-Biedl Syndrome (BBS11). This disorder is associated with obesity, retinopathy, diabetes, polydactyly, renal abnormalities, learning disability, and hypogenitalism. It is likely that C-terminal mutations in TRIM32 affect the ability of muscle proteins to be degraded by the ubiquitin-proteasome pathway.

Paradoxical contractile properties in the knee extensors of HIV-infected men treated with antiretroviral therapy

We assessed contractile properties in the knee extensors of 18 men with the human immunodeficiency virus (HIV+) being treated with antiretroviral therapy (ART), and 9 healthy controls matched for age and body mass index. We found significant, divergent differences between groups with regard to force relaxation. Half-times of twitch relaxation were shorter (62.6 ± 5.4 ms vs. 48.9 ± 3.0 ms; p = 0.045) and maximum rates of torque relaxation were slower (0.47% ± 0.04%(s-)1 vs. 1.32% ± 0.10%(s-)1; p < 0.001) in HIV+ individuals. These preliminary findings suggest potential intramuscular impairments in HIV+ individuals on ART, perhaps because of interactions between calcium handling and mitochondrial dysfunction.

Procysteine increases alcohol-depleted glutathione stores in rat plantaris following a period of abstinence

Aims: To assess the effectiveness of procysteine (PRO) supplementation provided during a period of abstinence (ABS) on alcohol-induced skeletal muscle atrophy and oxidant stress. Methods: Age- and gender-matched Sprague–Dawley rats were fed the Lieber–DeCarli liquid diet containing either alcohol or an isocaloric substitution (control diet) for 12 week. Next, subgroups of alcohol-fed rats were fed the control diet for 2 week (ABS) supplemented with either PRO (0.35%, w/v) or vehicle. Plantaris morphology was assessed by hematoxylin and eosin staining. Total, reduced and oxidized glutathione (GSH) levels and total antioxidant potential were determined by commercially available assay kits. Antibody arrays were used to determine cytokine levels. Real-time polymerase chain reaction was used to determine gene expressions of two E3 ubiquitin ligases, atrogin-1 and muscle ring finger protein-1 (MuRF-1). Results: Plantaris muscles from alcohol-fed rats displayed extensive atrophy, as well as decreased GSH levels, a trend for decreased total antioxidant potential and elevated atrogin-1 and MuRF-1 mRNA levels. GSH levels and total antioxidant potential continued to decrease during 2 weeks of ABS from alcohol, which were normalized in abstinent rats provided PRO. Gene levels of both E3 ligases returned to baseline during ABS. In parallel, plantaris cross-sectional area increased in both groups during ABS. Conclusions: PRO supplementation during ABS significantly attenuated alcohol-induced redox stress compared with untreated abstinent rats. Thus, our data may suggest that GSH restoration therapy may provide therapeutic benefits to the overall antioxidant state of skeletal muscle when prescribed in conjunction with an established detoxification program for recovering alcoholics.

Models of accelerated sarcopenia: critical pieces for solving the puzzle of age-related muscle atrophy

Sarcopenia, the age-related loss of skeletal muscle mass, is a significant public health concern that continues to grow in relevance as the population ages. Certain conditions have the strong potential to coincide with sarcopenia to accelerate the progression of muscle atrophy in older adults. Among these conditions are co-morbid diseases common to older individuals such as cancer, kidney disease, diabetes, and peripheral artery disease. Furthermore, behaviors such as poor nutrition and physical inactivity are well-known to contribute to sarcopenia development. However, we argue that these behaviors are not inherent to the development of sarcopenia but rather accelerate its progression. In the present review, we discuss how these factors affect systemic and cellular mechanisms that contribute to skeletal muscle atrophy. In addition, we describe gaps in the literature concerning the role of these factors in accelerating sarcopenia progression. Elucidating biochemical pathways related to accelerated muscle atrophy may allow for improved discovery of therapeutic treatments related to sarcopenia.

Role of reactive metabolites in drug-induced hepatotoxicity

Drugs are generally converted to biologically inactive forms and eliminated from the body, principally by hepatic metabolism. However, certain drugs undergo biotransformation to metabolites that can interfere with cellular functions through their intrinsic chemical reactivity towards glutathione, leading to thiol depletion, and functionally critical macromolecules, resulting in reversible modification, irreversible adduct formation, and irreversible loss of activity. There is now a great deal of evidence which shows that reactive metabolites are formed from drugs known to cause hepatotoxicity, such as acetaminophen, tamoxifen, isoniazid, and amodiaquine. The main theme of this article is to review the evidence for chemically reactive metabolites being initiating factors for the multiple downstream biological events culminating in toxicity. The major objectives are to understand those idiosyncratic hepatotoxicities thought to be caused by chemically reactive metabolites and to define the role of toxic metabolites.

Combined effects of hyperglycemic conditions and HIV-1 Nef: a potential model for induced HIV neuropathogenesis

Hyperglycemic conditions associated with diabetes mellitus (DM) or with the use of antiretroviral therapy may increase the risk of central nervous system (CNS) disorders in HIV-1 infected patients. In support of this hypothesis, we investigated the combined effects of hyperglycemic conditions and HIV-1 accessory protein Nef on the CNS using both in vitro and in vivo models. Astrocytes, the most abundant glial cell type required for normal synaptic transmission and other functions were selected for our in vitro study. The results show that in vitro hyperglycemic conditions enhance the expression of proinflammatory cytokines including caspase-3, complement factor 3 (C3), and the production of total nitrate and 8-iso-PGF2 α as reactive oxygen species (ROS) in human astrocytes leading to cell death in a dose-dependent manner. Delivery of purified recombinant HIV-1 Nef protein, or Nef expressed via HIV-1-based vectors in astrocytes showed similar results. The expression of Nef protein delivered via HIV-1 vectors in combination with hyperglycemia further augmented the production of ROS, C3, activation of caspase-3, modulation of filamentous protein (F-protein), depolarization of the mitochondria, and loss of astrocytes. To further verify the effects of hyperglycemia and HIV-1 Nef protein on CNS individually or in combination, in vivo studies were performed in streptozotocin (STZ) induced diabetic mice, by injecting HIV-1 Nef expressing viral particles into the sub-cortical region of the brain. Our in vivo results were similar to in vitro findings indicating an enhanced production of caspases-3, ROS (lipid oxidation and total nitrate), and C3 in the brain tissues of these animals. Interestingly, the delivery of HIV-1 Nef protein alone caused similar damage to CNS as augmented by hyperglycemia conditions. Taken together, the data suggests that HIV-1 infected individuals with hyperglycemia could potentially be at a higher risk of developing CNS related complications.

Procysteine stimulates expression of key anabolic factors and reduces plantaris atrophy in alcohol-fed rats

BACKGROUND

Long-term alcohol ingestion may produce severe oxidant stress and lead to skeletal muscle dysfunction. Emerging evidence has suggested that members of the interleukin-6 (IL-6) family of cytokines play diverse roles in the regulation of skeletal muscle mass. Thus, our goals were (i) to minimize the degree of oxidant stress and attenuate atrophy by supplementing the diets of alcohol-fed rats with the glutathione precursor, procysteine, and (ii) to identify the roles of IL-6 family members in alcoholic myopathy.

METHODS

Age- and gender-matched Sprague-Dawley rats were fed the Lieber-DeCarli liquid diet containing either alcohol or an isocaloric substitution (control diet) for 35 weeks. Subgroups of alcohol-fed rats received procysteine (0.35%, w/v) for the final 12 weeks. Plantaris morphology was assessed by hematoxylin and eosin staining. Major components of glutathione metabolism were determined using assay kits. Real-time PCR was used to determine expression levels of several genes.

RESULTS

Plantaris muscles from alcohol-fed rats displayed extensive atrophy, as well as decreased glutathione levels, decreased activities of glutathione reductase and glutathione peroxidase, decreased superoxide dismutase (SOD)-2 (Mn-SOD2), and increased NADPH oxidase-1 gene expression-each indicative of significant oxidant stress. Alcohol also induced gene expression of catabolic factors including IL-6, oncostatin M, atrogin-1, muscle ring finger protein-1, and IGFBP-1. Procysteine treatment attenuated plantaris atrophy, restored glutathione levels, and increased catalase, Cu/Zn-SOD1, and Mn-SOD2 mRNA expression, but did not reduce other markers of oxidant stress or levels of these catabolic factors. Instead, procysteine stimulated gene expression of anabolic factors such as insulin-like growth factor-1, ciliary neurotrophic factor, and cardiotrophin-1.

CONCLUSIONS

Procysteine significantly attenuated, but did not completely abrogate, alcohol-induced oxidant stress or catabolic factors. Rather, procysteine minimized the extent of plantaris atrophy by inducing components of several anabolic pathways. Therefore, anti-oxidant treatments such as procysteine supplementation may benefit individuals with alcoholic myopathy.

Dilated cardiomyopathy in transgenic mice expressing HIV Tat

Mechanisms responsible for HIV cardiomyopathy are unknown, but may include direct effects of HIV proteins on the heart. Transgenic mice (TG) expressing HIV Tat protein targeted to the myocardium, +/- Tat TG, have revealed anatomical and biochemical defects in the heart. The present studies were conducted to clarify the effect of Tat on cardiac function. In vivo hemodynamics was measured in awake mice after inserting a catheter tip in the left ventricle under general anesthesia. Under the age of 3 months, the heart rate (HR) was significantly lower in TG (591 +/- 47 vs. 716 +/- 45 bpm, TG versus FVB control (FVB), respectively (P < 0.05; n = 8-12). Other hemodynamic indexes, including left ventricular systolic pressure (LVSP), positive and negative dp/dt (mmHg/s), and left ventricular end diastolic pressure (LVEDP) remained indistinguishable from FVB. At 6 months, however, ventricular dysfunction was evident in TG (HR = 580 +/- 47 vs. 673 +/- 25 bpm, TG versus FVB, P < 0.05); LVSP (132 +/- 6 vs. 147 +/- 6 mmHg, TG versus FVB; P < 0.05); LVEDP (15 +/- 4 vs. 8 +/- 6 mmHg, TG vs. FVB, P < 0.05); +dp/dt = 8872 +/- 331 vs. 10026 +/- 796 mmHg/s TG versus FVB, P < 0.01) and -dp/dt (7403 +/- 432 vs. 8835 +/- 368 mmHg/s, TG versus FVB, P < 0.01; n = 8-12, in each group). The change in percentage of fractional shortening in response to isoproterenol was also significantly reduced in cardiac myocytes isolated from TG versus FVB (P < 0.05). Thus, targeted myocardial transgenic expression of HIV Tat in mice results in relative bradycardia, depression in systolic and diastolic functions in vivo, and blunted adrenergic responsiveness in vitro.

Calpain-1 is required for hydrogen peroxide-induced myotube atrophy

Recent reports suggest numerous roles for cysteine proteases in the progression of skeletal muscle atrophy due to disuse or disease. Nonetheless, a specific requirement for these proteases in the progression of skeletal muscle atrophy has not been demonstrated. Therefore, this investigation determined whether calpains or caspase-3 is required for oxidant-induced C2C12 myotube atrophy. We demonstrate that exposure to hydrogen peroxide (25 microM H2O2) induces myotube oxidative damage and atrophy, with no evidence of cell death. Twenty-four hours of exposure to H2O2 significantly reduced both myotube diameter and the abundance of numerous proteins, including myosin (-81%), alpha-actinin (-40%), desmin (-79%), talin (-37%), and troponin I (-80%). Myotube atrophy was also characterized by increased cleavage of the cysteine protease substrate alphaII-spectrin following 4 h and 24 h of H2O2 treatment. This degradation was blocked by administration of the protease inhibitor leupeptin (10 microM). Using small interfering RNA transfection of mature myotubes against the specific proteases calpain-1, calpain-2, and caspase-3, we demonstrated that calpain-1 is required for H2O2-induced myotube atrophy. Collectively, our data provide the first evidence for an absolute requirement for calpain-1 in the development of skeletal muscle myotube atrophy in response to oxidant-induced cellular stress.

SIRT1 longevity factor suppresses NF-kappaB -driven immune responses: regulation of aging via NF-kappaB acetylation?

The aging process involves changes in immune regulation, i.e. adaptive immunity declines whereas innate immunity becomes activated. NF-kappaB signaling is the master regulator of the both immune systems. Two recent articles highlight the role of the NF-kappaB system in aging and immune responses. Adler et al showed that the NF-kappaB binding domain is the genetic regulatory motif which is most strongly associated with the aging process. Kwon et al studying HIV-1 infection and subsequent immune deficiency process demonstrated that HIV-1 Tat protein binds to SIRT1 protein, a well-known longevity factor, and inhibits the SIRT1-mediated deacetylation of the p65 component of the NF-kappaB complex. As a consequence, the transactivation efficiency of the NF-kappaB factor was greatly potentiated, leading to the activation of immune system and later to the decline of adaptive immunity. These observations support the scenario where immune responses and aging process can be enforced by the potentiation of NF-kappaB transactivation efficiency. Longevity factors, such as SIRT1 and its activators, might regulate the efficiency of the NF-kappaB signaling, the major outcome of which is inflamm-aging via proinflammatory responses.

Skeletal and cardiac myopathy in HIV-1 transgenic rats

The mechanism by which human immunodeficiency virus (HIV)-1 infection in humans leads to the erosion of lean body mass is poorly defined. Therefore, the purpose of the present study was to determine whether transgenic (Tg) rats that constitutively overexpress HIV-1 viral proteins exhibit muscle wasting and to elucidate putative mechanisms. Over 7 mo, Tg rats gained less body weight than pair-fed controls exclusively as a result of a proportional reduction in lean, not fat, mass. Fast- and slow-twitch muscle atrophy in Tg rats did not result from a reduction in the in vivo-determined rate of protein synthesis. In contrast, urinary excretion of 3-methylhistidine, as well as the content of atrogin-1 and the 14-kDa actin fragment, was elevated in gastrocnemius of Tg rats, suggesting increased muscle proteolysis. Similarly, Tg rats had reduced cardiac mass, which was independent of a change in protein synthesis. This decreased cardiac mass was associated with a reduction in stroke volume, but cardiac output was maintained by a compensatory increase in heart rate. The HIV-induced muscle atrophy was associated with increased whole body energy expenditure, which was not due to an elevated body temperature or secondary bacterial infection. Furthermore, the atrophic response could not be attributed to the development of insulin resistance, decreased levels of circulating amino acids, or increased tissue cytokines. However, skeletal muscle and, to a lesser extent, circulating insulin-like growth factor I was reduced in Tg rats. Although hepatic injury was implicated by increased plasma levels of aspartate and alanine aminotransferases, hepatic protein synthesis was not different between control and Tg rats. Hence, HIV-1 Tg rats develop atrophy of cardiac and skeletal muscle, the latter of which results primarily from an increased protein degradation and may be related to the marked reduction in muscle insulin-like growth factor I.