HIV protease inhibitor ritonavir induces renal fibrosis and dysfunction: role of platelet-derived TGF-ß1 and intervention via antioxidant pathways.

OBJECTIVE: Chronic kidney disease (CKD) with tubular injury and fibrosis occurs in HIV infection treated with certain protease inhibitor-based antiretroviral therapies. The pathophysiology is unclear. DESIGN: We hypothesized that fibrosis, mediated by platelet-derived transforming growth factor (TGF)-ß1, underlies protease inhibitor-associated CKD. We induced this in mice exposed to the protease inhibitor ritonavir (RTV), and intervened with low-dose inhaled carbon monoxide (CO), activating erythroid 2-related factor (Nrf2)-associated antioxidant pathways. METHODS: Wild-type C57BL/6 mice and mice deficient in platelet TGF-ß1, were given RTV (10 mg/kg) or vehicle daily for 8 weeks. Select groups were exposed to CO (250 ppm) for 4 h after RTV or vehicle injection. Renal disorder, fibrosis, and TGF-ß1-based and Nrf2-based signaling were examined by histology, immunofluorescence, and flow cytometry. Renal damage and dysfunction were assessed by KIM-1 and cystatin C ELISAs. Clinical correlations were sought among HIV-infected individuals. RESULTS: RTV-induced glomerular and tubular injury, elevating urinary KIM-1 (P = 0.004). It enhanced TGF-ß1-related signaling, accompanied by kidney fibrosis, macrophage polarization to an inflammatory phenotype, and renal dysfunction with cystatin C elevation (P = 0.008). Mice lacking TGF-ß1 in platelets were partially protected from these abnormalities. CO inhibited RTV-induced fibrosis and macrophage polarization in association with upregulation of Nrf2 and heme oxygenase-1 (HO-1). Clinically, HIV infection correlated with elevated cystatin C levels in untreated women (n = 17) vs. age-matched controls (n = 19; P = 0.014). RTV-treated HIV+ women had further increases in cystatin C (n = 20; P = 0.05), with parallel elevation of HO-1. CONCLUSION: Platelet TGF-ß1 contributes to RTV-induced kidney fibrosis and dysfunction, which may be amenable to antioxidant interventions.

HIV protease inhibitor-induced cardiac dysfunction and fibrosis is mediated by platelet-derived TGF-ß1 and can be suppressed by exogenous carbon monoxide.

Human immunodeficiency virus (HIV) infection is an independent risk factor for cardiovascular disease. This risk is magnified by certain antiretrovirals, particularly the protease inhibitor ritonavir, but the pathophysiology of this connection is unknown. We postulated that a major mechanism for antiretroviral-associated cardiac disease is pathologic fibrosis linked to platelet activation with release and activation of transforming growth factor (TGF)-ß1, and that these changes could be modeled in a murine system. We also sought to intervene utilizing inhaled carbon monoxide (CO) as proof-of-concept for therapeutics capable of regulating TGF-ß1 signaling and collagen autophagy. We demonstrate decreased cardiac function indices, including cardiac output, ejection fraction and stroke volume, and prominent cardiac fibrosis, in mice exposed to pharmacological doses of ritonavir. Cardiac output and fibrosis correlated with plasma TGF-ß1 levels. Mice with targeted deletion of TGF-ß1 in megakaryocytes/platelets (PF4CreTgfb1flox/flox) were partially protected from ritonavir-induced cardiac dysfunction and fibrosis. Inhalation of low dose CO (250ppm), used as a surrogate for upregulation of inducible heme oxygenase/endogenous CO pathways, suppressed ritonavir-induced cardiac fibrosis. This occurred in association with modulation of canonical (Smad2) and non-canonical (p38) TGF-ß1 signaling pathways. In addition, CO treatment suppressed the M1 pro-inflammatory subset of macrophages and increased M2c regulatory cells in the hearts of RTV-exposed animals. The effects of CO were dependent upon autophagy as CO did not mitigate ritonavir-induced fibrosis in autophagy-deficient LC3-/- mice. These results suggest that platelet-derived TGF-ß1 contributes to ritonavir-associated cardiac dysfunction and fibrosis, extending the relevance of our findings to other antiretrovirals that also activate platelets. The anti-fibrotic effects of CO are linked to alterations in TGF-ß1 signaling and autophagy, suggesting a proof-of-concept for novel interventions in HIV/antiretroviral therapy-mediated cardiovascular disease.

The role of complement activation in thrombosis and hemolytic anemias.

OBJECTIVE: The objective of this study was to describe complement activation in hemostatic and pathologic states of coagulation and in the acquired and congenital hemolytic anemias. METHODS AND RESULTS: We review published and emerging data on the involvement of the classic, alternative and lectin-based complement pathways in coagulation and the hemolytic anemias. The alternative pathway in particular is always "on," at low levels, and is particularly sensitive to hyper-activation in a variety of physiologic and pathologic states including infection, autoimmune disorders, thrombosis and pregnancy, requiring tight control predicated on a variety of soluble and membrane bound regulatory proteins. In acquired hemolytic anemias such as paroxysmal nocturnal hemoglobinuria (PNH) and cold agglutinin disease (CAD), the complement system directly induces red blood cell injury, resulting in intravascular and extravascular hemolysis. In congenital hemolytic anemias such as sickle cell disease and ß-thalassemia, the complement system may also contribute to thrombosis and vascular disease. Complement activation may also lead to a storage lesion in red blood cells prior to transfusion. CONCLUSION: Complement pathways are activated in hemolytic anemias and are closely linked with thrombosis. In acquired disorders such as PNH and possibly CAD, inhibition of the alternative complement pathway improves clinical outcomes and reduces thrombosis risk. Whether complement inhibition has a similar role in congenital hemolytic anemias apart from the atypical hemolytic-uremic (aHUS)-type thrombotic microangiopathies remains to be determined.