Hyperlipidemia and inhibitors of HIV protease

Key Characteristics of Cardiovascular Toxicants

BACKGROUND

The concept of chemical agents having properties that confer potential hazard called key characteristics (KCs) was first developed to identify carcinogenic hazards. Identification of KCs of cardiovascular (CV) toxicants could facilitate the systematic assessment of CV hazards and understanding of assay and data gaps associated with current approaches.

OBJECTIVES

We sought to develop a consensus-based synthesis of scientific evidence on the KCs of chemical and nonchemical agents known to cause CV toxicity along with methods to measure them.

METHODS

An expert working group was convened to discuss mechanisms associated with CV toxicity.

RESULTS

The group identified 12 KCs of CV toxicants, defined as exogenous agents that adversely interfere with function of the CV system. The KCs were organized into those primarily affecting cardiac tissue (numbers 1-4 below), the vascular system (5-7), or both (8-12), as follows: 1) impairs regulation of cardiac excitability, 2) impairs cardiac contractility and relaxation, 3) induces cardiomyocyte injury and death, 4) induces proliferation of valve stroma, 5) impacts endothelial and vascular function, 6) alters hemostasis, 7) causes dyslipidemia, 8) impairs mitochondrial function, 9) modifies autonomic nervous system activity, 10) induces oxidative stress, 11) causes inflammation, and 12) alters hormone signaling.

DISCUSSION

These 12 KCs can be used to help identify pharmaceuticals and environmental pollutants as CV toxicants, as well as to better understand the mechanistic underpinnings of their toxicity. For example, evidence exists that fine particulate matter [PM ≤2.5μm in aerodynamic diameter (PM2.5)] air pollution, arsenic, anthracycline drugs, and other exogenous chemicals possess one or more of the described KCs. In conclusion, the KCs could be used to identify potential CV toxicants and to define a set of test methods to evaluate CV toxicity in a more comprehensive and standardized manner than current approaches. https://doi.org/10.1289/EHP9321.

A rodent model of HIV protease inhibitor indinavir induced peripheral neuropathy

HIV-associated sensory neuropathy (HIV-SN) is the most frequent manifestation of HIV disease. It often presents with significant neuropathic pain and is associated with previous exposure to neurotoxic nucleoside reverse transcriptase inhibitors. However, HIV-SN prevalence remains high even in resource-rich settings where these drugs are no longer used. Previous evidence suggests that exposure to indinavir, a protease inhibitor commonly used in antiretroviral therapy, may link to elevated HIV-SN risk. Here, we investigated whether indinavir treatment was associated with the development of a "dying back" axonal neuropathy and changes in pain-relevant limb withdrawal and thigmotactic behaviours. After 2 intravenous injections of indinavir (50 mg/kg, 4 days apart), adult rats developed hind paw mechanical hypersensitivity, which peaked around 2 weeks post first injection (44% reduction from baseline). At this time, animals also had (1) significantly changed thigmotactic behaviour (62% reduction in central zone entries) comparing with the controls and (2) a significant reduction (45%) in hind paw intraepidermal nerve fibre density. Treatment with gabapentin, but not amitriptyline, was associated with a complete attenuation of hind paw mechanical hypersensitivity observed with indinavir treatment. Furthermore, we found a small but significant increase in microglia with the effector morphology in the lumbar spinal dorsal horn in indinavir-treated animals, coupled with significantly increased expression of phospho-p38 in microglia. In summary, we have reported neuropathic pain-related sensory and behavioural changes accompanied by a significant loss of hind paw skin sensory innervation in a rat model of indinavir-induced peripheral neuropathy that is suitable for further pathophysiological investigation and preclinical evaluation of novel analgesics.

Cardiovascular Complications of HIV in Endemic Countries

Effective combination antiretroviral therapy (ART) has enabled human immunodeficiency virus (HIV) infection to evolve from a generally fatal condition to a manageable chronic disease. This transition began two decades ago in high-income countries and has more recently begun in lower income, HIV endemic countries (HIV-ECs). With this transition, there has been a concurrent shift in clinical and public health burden from AIDS-related complications and opportunistic infections to those associated with well-controlled HIV disease, including cardiovascular disease (CVD). In the current treatment era, traditional CVD risk factors and HIV-related factors both contribute to an elevated risk of myocardial infarction, stroke, heart failure, and arrhythmias. In HIV-ECs, the high prevalence of persons living with HIV and growing prevalence of CVD risk factors will contribute to a growing epidemic of HIV-associated CVD. In this review, we discuss the epidemiology and pathophysiology of cardiovascular complications of HIV and the resultant implications for public health efforts in HIV-ECs.

Update on HIV Lipodystrophy

When prescribed appropriately and taken adherently, antiretroviral therapy can consistently and durably suppress HIV replication, potentially translating into years of near normal health for HIV-infected persons. However, presently available antiretrovirals are associated with a cluster of physical and metabolic symptoms termed HIV lipodystrophy. This article reviews the state of knowledge about the pathogenesis and treatment of the various manifestations of these adverse effects.

Pregnane X receptor mediates dyslipidemia induced by the HIV protease inhibitor amprenavir in mice

Human immunodeficiency virus (HIV) protease inhibitors (PIs) have been used successfully in extending the life span of people infected with HIV. The use of PIs has also been associated with dyslipidemia and an increased risk of cardiovascular disease, but the underlying mechanisms remain elusive. Several PIs have been implicated in activating the nuclear receptor pregnane X receptor (PXR), which acts as a xenobiotic sensor to regulate xenobiotic metabolism in the liver and intestine. Recent studies indicate that PXR may also play an important role in the regulation of lipid homeostasis. In the present study, we identified amprenavir, a widely used HIV PI, as a potent PXR-selective agonist. Computational docking studies combined with site-direct mutagenesis identified several key residues within the ligand-binding pocket of PXR that constitute points of interaction with amprenavir. Amprenavir efficiently activated PXR and induced PXR target gene expression in vitro and in vivo. Short-term exposure to amprenavir significantly increased plasma total cholesterol and atherogenic low-density lipoprotein cholesterol levels in wild-type mice, but not in PXR-deficient mice. Amprenavir-mediated PXR activation stimulated the expression of several key intestinal genes involved in lipid homeostasis. These findings provide critical mechanistic insight for understanding the impact of PIs on cardiovascular disease and demonstrate a potential role of PXR in mediating the adverse effects of HIV PIs in humans.

Ritonavir-induced lipoatrophy and dyslipidaemia is reversed by the anti-inflammatory drug leflunomide in a PPAR-γ-dependent manner

BACKGROUND

The complex interplay between viral infection and virus-activated inflammatory pathways with protease inhibitors (PIs) contributes to the increased risk of developing atherosclerosis and coronary artery disease in HIV-infected patients. Leflunomide is an antirheumatic drug whose administration to HIV-1-infected persons effectively decreases T-cell turnover and activation. In this study we have investigated the effects of leflunomide on dyslipidaemia and lipodistrophy induced by ritonavir in rodents.

METHODS

Mice were administered ritonavir (5 mg/kg/day) alone or in combination with leflunomide (40 mg/kg/day) for 12 days. Expression of nuclear receptor and lipidogenetic genes was measured in liver and adipose tissues.

RESULTS

Administration of the HIV PI ritonavir to mice increased plasma triacylglycerols, free fatty acids and cholesterol levels, and this effect was reverted by cotreatment with leflunomide. Ritonavir administration was associated with reduced epididymal fat/body weight ratio and increased liver content of triacylglycerols content. These effects were reverted by leuflunomide. Histopathology analysis shows that exposure to ritonavir causes inflammation of epididymal fat as demonstrated by dense leukocytes infiltration as well as by increased levels of proinflammatory mediators and reduced expression and activity of peroxisome proliferator-activated receptor-γ (PPAR-γ). Leflunomide reduced epididymal fat inflammatory-metabolic alteration induced by ritonavir and restored PPAR-γ expression in the epididymal fat.

CONCLUSIONS

We have shown that the anti-inflammatory drug leflunomide protects against ritonavir-induced inflammation and dysmetabolism in adipose tissue and might be a promising strategy in the setting of HIV-infected patients at risk for HIV-induced dyslipidaemia.

Determination of the antiretroviral drug tenofovir in plasma from HIV-infected adults by ultrafast isotope dilution MALDI-triple quadrupole tandem mass spectrometry

A new and reliable mass spectrometric method using an isotope dilution method in combination with matrix-assisted laser desorption/ionization-triple quadrupole tandem mass spectrometry (ID-MALDI-QqQ-MS/MS) has been developed and validated for the determination of concentrations of the antiretroviral drug tenofovir (TNV) in plasma from HIV-infected adults. The advantage of this new method is that (1) the method is ultrafast and (2) can be applied for high-throughput measurement of TNV in plasma. The method is based on a simple plasma deproteinization step in combination with the use of [adenine-(13) C(5) ]-TNV as the internal standard. TNV and [adenine-(13) C(5) ]-TNV were monitored by multiple reaction monitoring using the transition m/z 288.0 → 176.2 and m/z 293.2 → 181.2 for TNV and [adenine-(13) C(5) ]-TNV, respectively. The method was validated according to the most recent FDA guidelines for the development and validation of (new) bio-analytical assays. Validated method parameters were: linearity, accuracy, precision and stability of the method. The lowest limit of quantification was 0.10 µmol/l, whereas the limit of detection determined at a signal-to-noise ratio (S/N = 3:1) in pooled drug free human control plasma was 0.04 µmol/l. The validated method was successfully applied and tested for its clinical feasibility by the analysis of plasma samples from selected HIV-infected adults receiving the prodrug tenofovir disoproxil fumarate. Observed plasma TNV concentrations ranged between 0.11 and 0.76 µmol/l and measured plasma TNV concentrations were within the therapeutically relevant concentration range.

The bile acid sensor FXR protects against dyslipidemia and aortic plaques development induced by the HIV protease inhibitor ritonavir in mice

BACKGROUND

Although human immunodeficiency virus (HIV)-related morbidity and mortality rates in patients treated with a combination of high active antiretroviral therapy (HAART) have declined, significant metabolic/vascular adverse effects associated with the long term use of HIV protease inhibitors (PIs) have emerged as a significant side effect. Here we illustrate that targeting the bile acid sensor farnesoid X receptor (FXR) protects against dyslipidemia and vascular injury induced HIV-PIs in rodents.

METHODOLOGY/PRINCIPAL FINDINGS

Administration of the HIV PI ritonavir to wild type mice increased plasma triacylglycerols and cholesterol levels and this effect was exacerbated by dosing ritonavir to mice harbouring a disrupted FXR. Dyslipidemia induced by ritonavir associated with a shift in the liver expression of signature genes, Sterol Regulatory Element-Binding Protein (SREBP)-1 and fatty acid synthase. Treating wild type mice with the FXR agonist (chenodeoxycholic acid, CDCA) protected against development of dyslipidemia induced by ritonavir. Administration of ritonavir to ApoE(-/-) mice, a strain that develop spontaneously atherosclerosis, increased the extent of aortic plaques without worsening the dyslipidemia. Treating these mice with CDCA reduced the extent of aortic plaques by 70% without changing plasma lipoproteins or the liver expression of signature genes. A beneficial effect on aortic plaques was also obtained by treating ApoE(-/-) mice with gemfibrozil, a PPARα agonist. FXR activation counter-regulated induction of expression/activity of CD36 caused by HIV-PIs in circulating monocytes and aortic plaques. In macrophages cell lines, CDCA attenuated CD36 induction and uptake of acetylated LDL caused by ritonavir. Natural and synthetic FXR ligands reduced the nuclear translocation of SREBP1c caused by ritonavir.

CONCLUSIONS/SIGNIFICANCE

Activation of the bile acid sensor FXR protects against dyslipidemia and atherosclerotic caused by ritonavir, a widely used HIV PI. From a mechanistic stand point it appears that besides reducing the liver expression of genes involved in fatty acid synthesis, FXR activation counter-regulates the expression/activity of CD36 on monocytes. FXR ligands might hold promise in the treatment dyslipidemia induced by ritonavir.

Efficacy and safety of atazanavir-ritonavir plus abacavir-lamivudine or tenofovir-emtricitabine in patients with hyperlipidaemia switched from a stable protease inhibitor-based regimen including one thymidine analogue

Randomized, open-label, prospective clinical trial assessing efficacy and safety on hyperlipidemia of a switching from a regimen including one protease inhibitor and one thymidine analogue to atazanavir/ritonavir plus abacavir/lamivudine or tenofovir/emtricitabine. Adult HIV-infected patients on their first antiretroviral therapy (of at least 48-week duration), including one protease inhibitor and zidovudine or stavudine, with stable immunovirologic features, and having diagnosis of persisting hyperlipidemia, were randomized to replace current treatment with atazanavir/ritonavir plus abacavir/lamivudine (arm A) or tenofovir/emtricitabine (arm B), and were followed for 48 weeks. Eighty-nine patients were enrolled: 42 patients were randomized to arm A, and 47 to arm B. At the end of the 48-week follow-up, incidence of virologic failure was comparable in both arms, and associated with a poor drug compliance. Increase in CD4 lymphocyte count was significantly higher in arm A after a 24-week study period (62.5 versus 39.2 x 10(6) cells/L; p < 0.05), while immunologic responses were comparable at the end of 48-week follow-up (91.5 versus 83.6; p > 0.05). A statistically significant reduction (-15.4%) in mean triglyceridaemia versus respective baseline values was reported in both groups (p < 0.05), without statistically significant difference between arm A and B. Similar results were reported for total cholesterol and low-density lipoprotein (LDL) cholesterol levels. Safety and tolerability profiles were comparable in both groups. Switching from a protease inhibitor- and thymidine analogue-based antiretroviral regimen to atazanavir/ritonavir plus abacavir/lamivudine or tenofovir/emtricitabine proved effective in the management of hyperlipidemia, without significant differences in lipid-lowering effect, virologic efficacy, and safety profile between these regimens.

New options in the treatment of lipid disorders in HIV-infected patients

Since the introduction of HAART, there was a remarkably change in the natural history of HIV disease, leading to a notable extension of life expectancy, although prolonged metabolic imbalances could significantly act on the longterm prognosis and outcome of HIV-infected persons, and there is an increasing concern about the cardiovascular risk in this population. Current recommendations suggest that HIV-infected perons undergo evaluation and treatment on the basis of the Third National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (NCEP ATP III) guidelines for dyslipidemia, with particular attention to potential drug interactions with antiretroviral agents and maintenance of virologic control of HIV infection. While a hypolipidemic diet and physical activity may certainly improve dyslipidemia, pharmacological treatment becomes indispensable when serum lipid are excessively high for a long time or the patient has a high cardiovascular risk, since the suspension or change of an effective antiretroviral therapy is not recommended. Moreover, the choice of a hypolipidemic drug is often a reason of concern, since expected drug-drug interactions (especially with antiretroviral agents), toxicity, intolerance, effects on concurrent HIV-related disease and decrease patient adherence to multiple pharmacological regimens must be carefully evaluated. Often the lipid goals of patients in this group are not achieved by the therapy recommended in the current lipid guidelines and in this article we describe other possibilities to treat lipid disorders in HIV-infected persons, like rosuvastatin, ezetimibe and fish oil.

Substitution of nevirapine or efavirenz for protease inhibitor versus lipid-lowering therapy for the management of dyslipidaemia

OBJECTIVES

To evaluate simplified protease inhibitor (PI)-sparing antiretroviral treatment versus lipid-lowering therapy for the management of highly active antiretroviral therapy (HAART)-induced hyperlipidaemia.

DESIGN

Randomized, open-label clinical trial assessing the efficacy on hyperlipidaemia of a switching therapy from PI to non-nucleoside reverse transcriptase inhibitor (NNRTI) nevirapine or efavirenz versus a hypolipidaemic treatment (with pravastatin or bezafibrate) added to current, unchanged antiretroviral combination.

METHODS

All HIV-infected patients on their first HAART regimen, with stable immuno-virological features, naive to all NNRTIs, and with mixed hyperlipidaemia, were randomized to replace PI with nevirapine (arm A) or efavirenz (arm B), or to receive pravastatin (arm C) or bezafibrate (arm D) with unchanged HAART regimen, and were followed-up for 12 months.

RESULTS

One hundred and thirty patients were evaluated: 29 patients were randomized to arm A, 34 to arm B, 36 to arm C, and 31 to arm D. At the end of the 12-month follow-up, a reduction of 25.2, 9.4, 41.2 and 46.6% in mean triglyceridaemia versus respective baseline values was reported in groups A, B, C and D, respectively, with statistically significant difference between arms A-B and C-D (P < 0.01). Similar results were reported for total and low-density lipoprotein cholesterol levels. Viro-immunological efficacy and tolerability profile were comparable in all considered arms.

CONCLUSION

Pravastatin and bezafibrate proved significantly more effective in the management of HAART-related hyperlipidaemia than the switching therapy from PI to nevirapine or efavirenz.

Abnormalities in apolipoprotein and lipid levels in an HIV-infected Brazilian population under different treatment profiles: the relevance of apolipoprotein E genotypes and immunological status

HIV infection is associated with disturbances in lipid metabolism due to a host's response mechanism and the current antiretroviral therapy. The pathological appearance and progression of atherosclerosis is dependent on the presence of injurious agents in the vascular endothelium and variations in different subsets of candidate genes. Therefore, the Hha I polymorphism in the apolipoprotein E gene was evaluated in addition to triglycerides, total cholesterol, very low-density lipoprotein (VLDL), LDL, high-density lipoprotein (HDL), and apolipoprotein (apo) Al, B and E levels in 86 Brazilian HIV-infected patients and 29 healthy controls. The allele frequency for apoE in the HIV-infected group and controls was in agreement with data on the Brazilian population. Dyslipidemia was observed in the HIV group and verified by increased levels of triglycerides, VLDL and apoE, and decreased levels of HDL and apoAl. The greatest abnormalities in these biochemical variables were shown in the HIV-infected individuals whose immune function was more compromised. The effect of the genetic variation at the APOE gene on biochemical variables was more pronounced in the HIV-infected individuals who carried the apoE2/3 genotype. The highly active anti-retroviral therapy (HAART)-receiving group presented increased levels of total cholesterol and apoE. Dyslipidemia was a predictable consequence of HIV infection and the protease inhibitors intensified the increase in apoE values.

Adiponectin ameliorates dyslipidemia induced by the human immunodeficiency virus protease inhibitor ritonavir in mice

Although the clinical application of HIV protease inhibitors (PIs) has markedly reduced HIV-related morbidity and mortality, it is now recognized that PI-based therapy often causes serious metabolic disorders, including hyperlipidemia and premature atherosclerosis. The etiology of these adverse effects remains obscure. Here, we demonstrate that deficiency of the fat-derived hormone adiponectin might play a role. The steady-state mRNA levels of the adiponectin gene and secretion of this protein from 3T3-L1 adipocytes are significantly decreased after treatment with several PIs (indinavir, nelfinavir, and ritonavir), with ritonavir having the greatest effect. Intragastric administration of ritonavir into mice decreases plasma concentrations of adiponectin and concurrently increases the plasma levels of triglyceride, free fatty acids, and cholesterol. Adiponectin replacement therapy markedly ameliorates ritonavir-induced elevations of triglyceride and free fatty acids. These beneficial effects of adiponectin are partly due to its ability to decrease ritonavir-induced synthesis of fatty acids and triglyceride, and to increase fatty acid combustion in the liver tissue. In contrast, adiponectin has little effect on ritonavir-induced hypercholesterolemia and hepatic cholesterol synthesis. These results suggest that hypoadiponectinemia is partly responsible for the metabolic disorders induced by HIV PIs, and adiponectin or its agonists might be useful for the treatment of these disorders.

Hyperlipidaemia in patients with HIV-1 infection receiving highly active antiretroviral therapy: epidemiology, pathogenesis, clinical course and management

A wide range of abnormalities of lipid metabolism have been recently described in HIV-infected patients receiving a protease inhibitor (PI)-based highly active antiretroviral therapy, including hypertriglyceridaemia and hypercholesterolaemia. The increase of plasma lipid concentrations may involve up to 70-80% of HIV-positive subjects treated with a PI-containing regimen and are frequently (but not always) associated with the fat redistribution or the lipodystrophy syndrome. Multiple pathogenetic mechanisms by which antiretroviral agents lead to dyslipidaemia have been hypothesized, but they are still controversial. The potential clinicopathological consequences of HIV-associated hyperlipidaemia are not completely known, but several anecdotal observations report an increased risk of premature coronary artery diseases in young HIV-positive individuals receiving PIs, besides peripheral atherosclerosis and acute pancreatitis. A limited-to-significant improvement of increased triglyceride and cholesterol plasma levels was described in patients who replaced PIs with nevirapine, efavirenz or abacavir, but the risks of long-term toxicity and virological relapse of this treatment switching are not completely defined. A hypolipidaemic diet and regular physical exercise may act favorably on dyslipidaemia, but pharmacological therapy becomes necessary when hyperlipidaemia is severe or persists for a long time. The choice of hypolipidaemic drugs is problematic because of potential pharmacological interactions with antiretroviral compounds and other antimicrobial agents, associated with an increased risk of toxicity and intolerance. Statins are considered the first-line therapy for the PI-related hypercholesterolaemia, while fibrates are the cornerstone of drug therapy when predominant hypertriglyceridaemia is of concern.

Management of metabolic complications of therapy

Considerable efforts are underway to define effective strategies for the treatment of metabolic complications of HIV therapy. Clearly these problems dominate the overall approach to treatment of HIV infection in the settings where antiretroviral agents are accessible. While progress has been made it has been slow, and accompanied by disappointments. There are currently no effective treatments for lipoatrophy, and while treatments for dyslipidemia have been described, in most cases the improvement is incomplete. While these efforts must continue it is hoped that a new focus on prevention of metabolic complications will begin to emerge in the year ahead.

Statins and fibrates for the treatment of hyperlipidaemia in HIV-infected patients receiving HAART

OBJECTIVES

The aim of our work is to evaluate the role of statins and fibrates in the management of hyperlipidaemia in HIV-infected patients receiving highly active antiretroviral therapy.

DESIGN

Open-label, randomized, prospective study of the efficacy and safety of bezafibrate, gemfibrozil, fenofibrate, pravastatin and fluvastatin as pharmacologic treatment for protease inhibitor-related dyslipidaemia.

METHODS

Plasma lipid levels of 656 HIV-infected patients who referred to our tertiary care centre and were on protease inhibitor-based antiretroviral therapy for at least 12 months have been evaluated. All patients had HIV viral load < 50 copies/ml and presented with hypertriglyceridaemia of at least 6 months duration that was unresponsive to a hypolipidaemic diet; all have been treated with bezafibrate, gemfibrozil, fenofibrate, pravastatin, or fluvastatin for 12 months.

RESULTS

Of the 656 patients observed 113 (17.2%) received pharmacological therapy, while seven patients were excluded from evaluation due to early drop-out. Of the 106 evaluable subjects, bezafibrate was used in 25 cases, gemfibrozil in 22, fenofibrate in 22, pravastatin in 19, and fluvastatin in 18. At the close of 1-year follow-up, fibrates led to a reduction of 40.7% and 21.9% versus baseline triglyceridaemia and cholesterolaemia, respectively (P < 0.001), and statins led to a reduction of 34.8% and 25.2% versus baseline triglyceride and total cholesterol levels, respectively (P < 0.001), without significant differences according to each different administered hypolipidaemic drug.

CONCLUSIONS

All administered statins and fibrates revealed a similar, significant efficacy in the treatment of diet-resistant hyperlipidaemia, and showed a favourable tolerability profile.

Recent trends in lipid management: raising the bar and shifting the goalposts?

The National Heart Foundation of Australia, in conjunction with the Cardiac Society of Australia and New Zealand, updated its Lipid Guidelines at the end of 2001, but on-going modification is anticipated to stay abreast of the rapid progress in this field. Research at all levels re-affirms the fundamental importance of lipid metabolism in many physiological and pathological processes. In addition, clinical trials such as the recent Heart Protection Study broaden the indications for intervention. The present review summarizes recent advances and analyzes emerging attitudes towards diagnosis and management that will influence future recommendations and practice.

HIV protease inhibitors promote atherosclerotic lesion formation independent of dyslipidemia by increasing CD36-dependent cholesteryl ester accumulation in macrophages

Protease inhibitors decrease the viral load in HIV patients, however the patients develop hypertriglyceridemia, hypercholesterolemia, and atherosclerosis. It has been assumed that protease inhibitor-dependent increases in atherosclerosis are secondary to the dyslipidemia. Incubation of THP-1 cells or human PBMCs with protease inhibitors caused upregulation of CD36 and the accumulation of cholesteryl esters. The use of CD36-blocking antibodies, a CD36 morpholino, and monocytes isolated from CD36 null mice demonstrated that protease inhibitor-induced increases in cholesteryl esters were dependent on CD36 upregulation. These data led to the hypothesis that protease inhibitors induce foam cell formation and consequently atherosclerosis by upregulating CD36 and cholesteryl ester accumulation independent of dyslipidemia. Studies with LDL receptor null mice demonstrated that low doses of protease inhibitors induce an increase in the level of CD36 and cholesteryl ester in peritoneal macrophages and the development of atherosclerosis without altering plasma lipids. Furthermore, the lack of CD36 protected the animals from protease inhibitor-induced atherosclerosis. Finally, ritonavir increased PPAR-gamma and CD36 mRNA levels in a PKC- and PPAR-gamma-dependent manner. We conclude that protease inhibitors contribute to the formation of atherosclerosis by promoting the upregulation of CD36 and the subsequent accumulation of sterol in macrophages.

Pathogenesis of HIV-associated cardiovascular complications

Reviews and studies published before the introduction of highly active antiretroviral therapy (HAART) have tracked the incidence and course of HIV infection in relation to cardiac illness in both children and adults. The introduction of HAART regimens has significantly modified the course of HIV disease, with longer survival rates and improvement of life quality in HIV-infected people expected. However, early data raised concerns about HAART being associated with an increase in both peripheral and coronary arterial diseases. In this review we discuss HIV-associated cardiovascular complications focusing on pathogenetic mechanisms that could have a role in diagnosis, management, and therapy of these complications in the HAART era.