Restoration of impaired endothelial myocyte enhancer factor 2 function rescues pulmonary arterial hypertension.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary arterioles, characterized by increased pulmonary arterial pressure and right ventricular failure. The cause of PAH is complex, but aberrant proliferation of the pulmonary artery endothelial cells (PAECs) and pulmonary artery smooth muscle cells is thought to play an important role in its pathogenesis. Understanding the mechanisms of transcriptional gene regulation involved in pulmonary vascular homeostasis can provide key insights into potential therapeutic strategies. METHODS AND RESULTS: We demonstrate that the activity of the transcription factor myocyte enhancer factor 2 (MEF2) is significantly impaired in the PAECs derived from subjects with PAH. We identified MEF2 as the key cis-acting factor that regulates expression of a number of transcriptional targets involved in pulmonary vascular homeostasis, including microRNAs 424 and 503, connexins 37, and 40, and Kruppel Like Factors 2 and 4, which were found to be significantly decreased in PAH PAECs. The impaired MEF2 activity in PAH PAECs was mediated by excess nuclear accumulation of 2 class IIa histone deacetylases (HDACs) that inhibit its function, namely HDAC4 and HDAC5. Selective, pharmacological inhibition of class IIa HDACs led to restoration of MEF2 activity in PAECs, as demonstrated by increased expression of its transcriptional targets, decreased cell migration and proliferation, and rescue of experimental pulmonary hypertension models. CONCLUSIONS: Our results demonstrate that strategies to augment MEF2 activity hold potential therapeutic value in PAH. Moreover, we identify selective HDAC IIa inhibition as a viable alternative approach to avoid the potential adverse effects of broad spectrum HDAC inhibition in PAH.

Thermal stability of rhodopsin and progression of retinitis pigmentosa: comparison of S186W and D190N rhodopsin mutants.

Over 100 point mutations in the rhodopsin gene have been associated with retinitis pigmentosa (RP), a family of inherited visual disorders. Among these, we focused on characterizing the S186W mutation. We compared the thermal properties of the S186W mutant with another RP-causing mutant, D190N, and with WT rhodopsin. To assess thermal stability, we measured the rate of two thermal reactions contributing to the thermal decay of rhodopsin as follows: thermal isomerization of 11-cis-retinal and hydrolysis of the protonated Schiff base linkage between the 11-cis-retinal chromophore and opsin protein. We used UV-visible spectroscopy and HPLC to examine the kinetics of these reactions at 37 and 55 °C for WT and mutant rhodopsin purified from HEK293 cells. Compared with WT rhodopsin and the D190N mutant, the S186W mutation dramatically increases the rates of both thermal isomerization and dark state hydrolysis of the Schiff base by 1-2 orders of magnitude. The results suggest that the S186W mutant thermally destabilizes rhodopsin by disrupting a hydrogen bond network at the receptor's active site. The decrease in the thermal stability of dark state rhodopsin is likely to be associated with higher levels of dark noise that undermine the sensitivity of rhodopsin, potentially accounting for night blindness in the early stages of RP. Further studies of the thermal stability of additional pathogenic rhodopsin mutations in conjunction with clinical studies are expected to provide insight into the molecular mechanism of RP and test the correlation between rhodopsin's thermal stability and RP progression in patients.

Human immunodeficiency virus downregulates podocyte apoE expression.

Apolipoprotein E (apoE) has been demonstrated to play an important role in providing protection against mesangial cell injury. In the present study, we evaluated the role of apoE and its associated downstream effects in human immunodeficiency virus (HIV)-associated nephropathy (HIVAN). Control (n = 6) and age- and sex-matched HIV-1 transgenic mice (Tg26, n = 6) were evaluated for their renal cortical expression of apoE. Renal tissue from Tg26 mice not only showed decreased apoE expression but also displayed downregulation of perlecan mRNA expression. In in vitro studies, conditionally immortalized human podocytes (CIHPs) were transduced with either NL4-3HIV (an HIV-1 construct lacking gag and pol, used for the development of Tg26 mouse model; NL4-3/CIHP) or empty vector (EV/CIHP); NL4-3/CIHPs and EV/CIHPs were studied for apoE mRNA expression. NL4-3/CIHPs showed reduction in apoE expression compared with EV/CIHPs. To evaluate the role of HIV-1 genes in the modulation of apoE expression, conditionally immortalized mouse podocytes (CIMPs) were transduced with individual HIV-1 gene constructs. Only nef-transduced CIMPs showed a decrease in apoE expression. To confirm this effect of nef in CIHPs, microarray analysis was performed in stable colonies of nef/CIHPs and EV/CIHPs. nef/CIHPs showed a 60% decrease in apoE and a 90% reduction in heparan sulfate mRNA expression. Moreover, nef transgenic mice showed a decrease in renal tissue expression of both apoE and perlecan. Both Tg26 and nef transgenic mice also showed areas of mesangial cell proliferation. These findings suggest that HIV-1-induced reduction in podocyte apoE expression and associated downregulation of podocyte perlecan might be contributing to mesangial cell (MC) phenotype in HIVAN.

Associations with retinal vascular occlusions in a diverse, urban population.

PURPOSE: Retinal vascular occlusions can lead to sudden and permanent visual impairment or blindness. Few epidemiological studies on retinal vascular occlusions have been conducted, especially on diverse populations. METHODS: This is a retrospective case-control study of all incident retinal vascular occlusions occurring during a three and one-half year study period at Montefiore Medical Center, capturing all potential cases by diagnosis codes. Patients with retinal venous occlusions (RVO) and retinal arterial occlusions (RAO) were analyzed separately and compared to age-matched control groups. RESULTS: All potential charts (n = 700) were reviewed, confirming 214 RVO and 35 RAO incident cases. In multivariable analyses, RVO was associated with type 2 diabetes mellitus (OR 2.41, p < 0.001), history of cerebrovascular accident (OR 2.14, p = 0.011), hypertension (OR 1.83, p = 0.004), glaucoma (OR 6.91, p < 0.001), black race (OR 3.72, p < 0.001), and male gender (OR 2.19 p < 0.001). RAO was significantly associated with current and former smoking combined (OR 8.95, p = 0.021) and male gender (OR 2.56, p = 0.038). CONCLUSION: Cardiovascular risk factors and glaucoma are reaffirmed as significant predictors of retinal vascular occlusions in a diverse patient population. Retinal vascular occlusions are more common in certain races and ethnicities, and further study into this may help identify high-risk individuals based on demographics.

Endothelium as a gatekeeper of fatty acid transport.

The endothelium transcends all clinical disciplines and is crucial to the function of every organ system. A critical, but poorly understood, role of the endothelium is its ability to control the transport of energy supply according to organ needs. Fatty acids (FAs) in particular represent a key energy source that is utilized by a number of tissues, but utilization must be tightly regulated to avoid potentially deleterious consequences of excess accumulation, including insulin resistance. Recent studies have identified important endothelial signaling mechanisms, involving vascular endothelial growth factor-B, peroxisome proliferator-activated receptor-γ, and apelin, that mediate endothelial regulation of FA transport. In this review, we discuss the mechanisms by which these signaling pathways regulate this key endothelial function.

Quality collaboratives and campaigns to reduce readmissions: what strategies are hospitals using?

BACKGROUND: Reducing hospital readmissions is a national priority, and many hospitals are participating in quality collaboratives or campaigns. OBJECTIVE: To describe and compare the current use of hospital strategies to reduce readmissions in 2 prominent quality initiatives-STAAR (State Action on Avoidable Rehospitalization) and H2H (Hospital-to-Home Campaign). DESIGN: Cross-sectional. METHODS: Web-based survey of hospitals that had enrolled in H2H or STAAR from May 2009 through June 2010, conducted from November 1, 2010 through June 30, 2011 (n = 599, response rate of 91%). We used standard frequency analysis and multivariable logistic regression to describe differences between STAAR and H2H hospitals. RESULTS: Many hospitals were not implementing several of the recommended strategies. Although STAAR hospitals tended to be more likely to implement several strategies, differences were attenuated when we adjusted for region and ownership type. In multivariable models, STAAR hospitals compared with H2H hospitals were more likely to ensure outpatient physicians were alerted within 48 hours of patient discharge (63% vs 38%, P < 0.001), and more likely to provide skilled nursing facilities the direct contact number of the inpatient treating physician for patients transferred (53% vs 34%, P = 0.001). H2H hospitals were more likely to assign responsibility for medication reconciliation to nurses usually or always (80% vs 54%, P = 0.001) and more likely to give most or all discharged patients referrals to cardiac rehabilitation services (59% vs 41%, P = 0.001). CONCLUSIONS: Substantial opportunity for improvement exists for hospitals engaged in STAAR or H2H quality initiatives.