Chronic hypoxia contributes to pulmonary hypertension through complex mechanisms that include enhanced NADPH oxidase expression and reactive oxygen species (ROS) generation in the lung. Stimulation of peroxisome proliferator-activated receptor g (PPARg) reduces the expression and activity of NADPH oxidase. Therefore, we hypothesized that activating PPARg with rosiglitazone would attenuate chronic hypoxia-induced pulmonary hypertension, in part, through suppressing NADPH oxidase-derived ROS that stimulate proliferative signaling pathways. Male C57Bl/6 mice were exposed to chronic hypoxia (CH, FI O 2 10%) or room air for 3 or 5 weeks. During the last 10 days of exposure, each animal was treated daily by gavage with either the PPARg ligand, rosiglitazone (10 mg/kg/d) or with an equal volume of vehicle. CH increased: (1) right ventricular systolic pressure (RVSP), (2) right ventricle weight, (3) thickness of the walls of small pulmonary vessels, (4) superoxide production and Nox4 expression in the lung, and (5) platelet-derived growth factor receptor b (PDGFRb) expression and activity and reduced phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression. Treatment with rosiglitazone prevented the development of pulmonary hypertension at 3 weeks; reversed established pulmonary hypertension at 5 weeks; and attenuated CH-stimulated Nox4 expression and superoxide production, PDGFRb activation, and reductions in PTEN expression. Rosiglitazone also attenuated hypoxia-induced increases in Nox4 expression in pulmonary endothelial cells in vitro despite hypoxia-induced reductions in PPARg expression. Collectively, these findings indicate that PPARg ligands attenuated hypoxia-induced pulmonary vascular remodeling and hypertension by suppressing oxidative and proliferative signals providing novel insights for mechanisms underlying therapeutic effects of PPARg activation in pulmonary hypertension.

Muscle LIM protein (MLP) is a cytoskeletal LIM-only protein expressed in striated muscle. Mutations in human MLP are associated with cardiomyopathy; however, the molecular mechanism by which MLP functions is not established. A Drosophila MLP homolog, mlp84B, displays many of the same features as the vertebrate protein, illustrating the utility of the fly for the study of MLP function. Animals lacking Mlp84B develop into larvae with a morphologically intact musculature, but the mutants arrest during pupation with impaired muscle function. Mlp84B displays muscle-specific expression and is a component of the Z-disc and nucleus. Preventing nuclear retention of Mlp84B does not affect its function, indicating that Mlp84B site of action is likely to be at the Z-disc. Within the Z-disc, Mlp84B is colocalized with the N-terminus of D-titin, a protein crucial for sarcomere organization and stretch mechanics. The mlp84B mutants phenotypically resemble weak D-titin mutants. Furthermore, reducing D-titin activity in the mlp84B background leads to pronounced enhancement of the mlp84B muscle defects and loss of muscle structural integrity. The genetic interactions between mlp84B and D-titin reveal a role for Mlp84B in maintaining muscle structural integrity that was not obvious from analysis of the mlp84B mutants themselves, and suggest Mlp84B and D-titin cooperate to stabilize muscle sarcomeres.

Objective: To explore the role of PPARγ in vascular regulation, endothelial PPARγ‐deficient mice (ePPARγ−/−) were subjected to studies of systemic vascular function. Methods: Mice with a floxed PPARγ gene were bred with mice expressing Cre recombinase driven by the endothelial promoter, Tie‐2. Subsequent ePPARγ−/− mice were selected by genotyping. Blood pressure of littermate control (Control) and ePPARγ−/− mice was monitored with telemetry. Aortic ring relaxation responses were determined in a muscle bath. Aortic nitric oxide (NO) production was measured with electron spin resonance spectroscopy and Fe(DETC)2. Aortic NF‐kB nuclear binding was detected by EMSA. Plasma levels of cysteine and cystine (Cys:CySS) were determined by HPLC, and derivatives of reactive oxygen metabolites (dROMs) by ELISA. Results: Compared to Controls, ePPARγ−/− animals did not demonstrate significant increases in mean arterial pressure. However, ePPARγ−/− mice displayed: 1) significant reductions in endothelium‐dependent vasorelaxation and aortic NO production, 2) increased aortic NF‐kB nuclear binding, and 3) increased vascular oxidative stress manifested as oxidation of the Cys:CySS redox couple and increased dROMs. Conclusion: Vascular endothelial PPARγ plays an important role in maintenance of redox balance in the vasculature. Supported by grants from the NIH, VA Research Service, and Takeda Pharmaceuticals.