Cell-permeable Cav1-mimetic peptide as a potential therapeutic for pulmonary hypertension and myocardial ischemic injury.

Overview

Pulmonary hypertension is a common disease characterized by high blood pressure in the arteries of the lungs which eventually leads to heart failure and death. None of the current drugs cure or halt the progression of this disease. Caveolin-1 (Cav-1) has recently been implicated in the development of pulmonary hypertension. For example, genetic ablation of the Cav-1 gene in mice results in pulmonary hypertension, lung remodeling and cardiac hypertrophy. Moreover, Lisanti and co-workers have reported a reduction of pulmonary Cav-1 expression in animal models of pulmonary hypertension. Decreases in both the Cav-1 gene and protein expression were also recently demonstrated in plexiform lesions of patients with severe pulmonary hypertension. Lisanti and co-workers recently demonstrated that short-term administration of a cell-permeable Cav-1-mimetic peptide prevented the development of monocrotaline-induced pulmonary hypertension and right ventricular hypertrophy in rats. Current research is focused on determining whether long-term administration of such a Cav-1 peptide can prevent and/or reverse the development of pulmonary hypertension and affect survival.

Introduction

Caveolae are small invaginations of the plasma membrane that are particularly abundant in cells of the cardio-pulmonary system such as endothelial cells, epithelial cells, fibroblasts, smooth muscle cells and cardiomyocytes. In these cell types, caveolae function both in protein trafficking and signal transduction, as well as in cholesterol homeostasis. Caveolins (Cavs) are the structural proteins that are both necessary and sufficient for the formation of caveolae. The caveolin gene family consists of three isoforms, namely Cav-1, Cav-2 and Cav-3. Cav-1 and Cav-2 are usually co-expressed and particularly abundant in endothelial cells, epithelial cells, fibroblasts and smooth muscle cells while Cav-3 is muscle specific and thus solely expressed in cardiac, skeletal and smooth muscle cells.

Caveolae are known to compartmentalize numerous signaling molecules such as the endothelial nitric oxide synthase (eNOS), protein kinase C (PKC), extracellular signal-regulated kinase-1/2 (ERK1/2) as well as different heterotrimeric G-proteins subunits. Most of the signaling molecules compartmentalized within the caveolar domains have been shown to interact with the Caveolin proteins. Using a phage display library, a Caveolin-binding motif sequence was identified asas _X_XXXX_XX_ where _ represents an aromatic amino acid and X represents any amino acid. Interestingly, this binding motif, which binds to the scaffolding domain of Cav-1 (residues 82 to 101) has been identified in numerous signaling proteins such as eNOS, ERK1/2, PKC and G? subunit. Interestingly, the interaction of the Cav-1 scaffolding domain with the Caveolin-binding motif appears to negatively regulate the activity of most of these associated-signaling proteins. For instance, Garcia-Cardena et al. (1997) demonstrated that incubation of eNOS with peptides corresponding to the Cav-1 scaffolding domain resulted in inhibition of eNOS activity in a dose dependent manner. Similarly, Lisanti and co-workers demonstrated that peptides corresponding to the Cav-1 scaffolding domain were also able to inhibit both MEK-1 and ERK1/2 activities. In many ways, Cav-1 serves both to compartmentalize and regulate cardiovascular signaling. As such, Cav-1 might play a prominent role in the pathogenesis of a wide-variety of cardiovascular diseases including cardiac hypertrophy and pulmonary hypertension, cardiomyopathy, cardiac fibrosis, stroke and myocardial ischemia.

Therapeutic Potential of a Cell-Permeable Cav-1-Mimetic Peptide

Interestingly, the coupling of molecules to a 16 amino acids peptide corresponding to the homeodomain of the Drosophila transcription factor antennapedia (AP or penetratin) has been shown to facilitate their uptake into cultured mammalian cells through a non-endocytic and non-degradative pathway. Accordingly, coupling of the Cav-1 scaffolding domain to the AP peptide (AP-Cav-1), was recently shown to facilitate its translocation across the cell membranes and to reduce inflammation, microvascular hyper-permeability and tumor progression in mice. Furthermore, perfusion of a Cav-1 scaffolding domain peptide was shown to exert cardioprotective effects in myocardial ischemia-reperfusion experiments. Importantly, Lisanti and co-workers recently demonstrated that short term administration of AP-Cav-1 prevented the development of MCT-induced pulmonary artery medial hypertrophy, PH and RV hypertrophy in rats. Mechanistically, these results demonstrate that short-term administration of AP-Cav-1 to MCT rats prevented the decreased expression of endogenous Cav-1, the hyper-activation of the STAT3 signaling cascade as well as the upregulation of cyclin D1 and D3 protein levels. The beneficial effect of AP-Cav-1 on the development of MCT-induced PH and RV hypertrophy could thus be attributed, at least in part, to the presence of normal endogenous Cav-1 proteins levels. Whether in vivo administration of APCav-1 could prevent the development of PH and RV hypertrophy in the absence of endogenous Cav-1 expression is under investigation.

Additionally, in vivo delivery of a cell-permeable Cav-1 scaffolding domain peptide (AP-Cav-1) has previously been shown to inhibit NO synthesis and, consequently, reduce inflammation, microvascular hyperpermeability and tumor progression in mice. Conversely, perfusion of a Cav-1 scaffolding domain peptide has been shown to exert cardioprotective effects by increasing endothelium-derived NO release as well as by reducing neutrophils adherence and infiltration in isolated-perfused rat hearts subjected to ischemia-reperfusion. The effect of in vivo administration of Caveolin-mimetic

Development Status

MTTI currently holds the rights to the cell-permeable Cav-1-mimetic peptide technology developed by Drs. Michael Lisanti and Jean Francois Jasmin while at Albert Einstein College of Medicine. Joint research efforts have been initiated between MTTI and Dr. Lisanti’s lab, currently at Thomas Jefferson University.

Research is being conducted to evaluate the potential therapeutic effect of a cell-permeable Caveolin-1-mimetic peptide on the development of pulmonary hypertension and the pathogenesis of myocardial ischemic injury. Pre-clinical studies will provide important information on the role of Caveolin-1 in these disease states, and may lead to the development of alternative treatments.