HIV-associated cardiomyopathy is a frequent and serious HIV complication, yet the underlying pathophysiology is poorly understood. Intriguingly, prior studies examining SIV as model for neuroAIDS have strongly implicated macrophage infiltration and activation as a key mechanism underlying neurodegeneration. A similar process may occur in the heart and, if so, trigger activation of matrix metalloproteinases that play an important role in chamber remodeling. Accordingly, the central hypothesis of this proposal is that functional cardiac impairment that develops in SIV-infected macaques results from both increased synthesis and activation of selective matrix metalloproteinases (MMPs) associated with macrophage infiltration and activation driven by SIV infection in the heart. The proposed studies will both define the temporal course of decline in cardiac function and its relationship to macrophage activation, SIV replication, and MMP activity, and determine the primary signaling cascades activating the MMPs that play a role in development of cardiomyopathy. There are 3 specific aims:
Aim One : To determine the evolution of cardiac dysfunction in SIV-infected macaques based on comprehensive serial echo Doppler and pressure-volume relation analysis and to define the relationship between cardiac dysfunction and inflammatory responses in the heart including myocardial macrophage activation. Host inflammatory responses and cardiomyocyte damage will be measured in endomyocardial biopsy and postmortem tissue samples by immunostaining and quantitative image analysis to compare with cardiac functional status.
Aim Two : To determine whether replication of macrophage-tropic SIV strains in the heart is a prerequisite for the development of cardiac dysfunction. To establish the relationship between viral replication and cardiac disease, we will measure myocardial viral load by real-time RT-PCR and identify the predominant replicating viral genotypes in the heart to compare with inflammatory responses including activation of myocardial macrophages, matrix metalloproteinase (MMP) production, and severity of cardiac dysfunction.
Aim Three : To determine whether activation of matrix metalloproteinases- specifically gelatinases MMP2 and MMP9, interstitial collagenases MMP1 and MMP13, and MMP12 (macrophage metalloelastase)-are stimulated by SIV-infection of macrophages in the heart and lead to cardiac dysfunction. Tissue inhibitors of MMPs (TIMPs) will also be quantified, and net enzyme protease activity assessed by in situ assay. In vitro studies will test whether a similar profile of MMP synthesis and activation can be produced by SIV-infected cultured macrophages to define the role of specific SIV genotypes present in dysfunctional hearts. These studies will set the stage for performing interventive studies in SIV-infected macaques using approaches to target specific MMPs to prevent cardiac dysfunction. ? ? ?
