Elastin haploinsufficiency accelerates age-related structural and functional changes in the renal microvasculature and impairment of renal hemodynamics in female mice

Age-related decline in functional elastin is associated with increased arterial stiffness, a known risk factor for developing cardiovascular disease. While the contribution of elastin insufficiency to the stiffening of conduit arteries is well described, little is known about the impact on the structure and function of the resistance vasculature, which contributes to total peripheral resistance and the regulation of organ perfusion. In this study, we determined how elastin insufficiency impinges on age-related changes in the structure and biomechanical properties of the renal microvasculature, altering renal hemodynamics and the response of the renal vascular bed to changes in renal perfusion pressure (RPP) in female mice. Using Doppler ultrasonography, we found that resistive index and pulsatility index were elevated in young Eln+/− and aged mice. Histological examination showed thinner internal and external elastic laminae, accompanied by increased elastin fragmentation in the medial layer without any calcium deposits in the small intrarenal arteries of kidneys from young Eln+/− and aged mice. Pressure myography of interlobar arteries showed that vessels from young Eln+/− and aged mice had a slight decrease in distensibility during pressure loading but a substantial decline in vascular recoil efficiency upon pressure unloading. To examine whether structural changes in the renal microvasculature influenced renal hemodynamics, we clamped neurohumoral input and increased renal perfusion pressure by simultaneously occluding the superior mesenteric and celiac arteries. Increased renal perfusion pressure caused robust changes in blood pressure in all groups; however, changes in renal vascular resistance and renal blood flow (RBF) were blunted in young Eln+/− and aged mice, accompanied by decreased autoregulatory index, indicating greater impairment of renal autoregulation. Finally, increased pulse pressure in aged Eln+/− mice positively correlated with high renal blood flow. Together, our data show that the loss of elastin negatively affects the structural and functional integrity of the renal microvasculature, ultimately worsening age-related decline in kidney function

Enhanced Membrane Binding of Oncogenic G Protein αqQ209L Confers Resistance to Inhibitor YM-254890

Heterotrimeric G proteins couple activated G protein-coupled receptors (GPCRs) to intracellular signaling pathways. They can also function independently of GPCR activation upon acquiring mutations that prevent GTPase activity and result in constitutive signaling, as occurs with the αqQ209L mutation in uveal melanoma. YM-254890 (YM) can inhibit signaling by both GPCR-activated WT αq and GPCR-independent αqQ209L. Although YM inhibits WT αq by binding to αq-GDP and preventing GDP/GTP exchange, the mechanism of YM inhibition of cellular αqQ209L remains to be fully understood. Here, we show that YM promotes a subcellular redistribution of αqQ209L from the plasma membrane (PM) to the cytoplasm. To test if this loss of PM localization could contribute to the mechanism of inhibition of αqQ209L by YM, we developed and examined N-terminal mutants of αqQ209L, termed PM-restricted αqQ209L, in which the addition of membrane-binding motifs enhanced PM localization and prevented YM-promoted redistribution. Treatment of cells with YM failed to inhibit signaling by these PM-restricted αqQ209L. Additionally, pull-down experiments demonstrated that YM promotes similar conformational changes in both αqQ209L and PM-restricted αqQ209L, resulting in increased binding to βγ and decreased binding to regulator RGS2, and effectors p63RhoGEF-DH/PH and phospholipase C-β. GPCR-dependent signaling by PM-restricted WT αq is strongly inhibited by YM, demonstrating that resistance to YM inhibition by membrane-binding mutants is specific to constitutively active αqQ209L. Together, these results indicate that changes in membrane binding impact the ability of YM to inhibit αqQ209L and suggest that YM contributes to inhibition of αqQ209L by promoting its relocalization

Targeting primary and metastatic uveal melanoma with a G protein inhibitor

Uveal melanoma (UM) is the most common intraocular tumor in adults. Nearly half of UM patients develop metastatic disease and often succumb within months because effective therapy is lacking. A novel therapeutic approach has been suggested by the discovery that UM cell lines driven by mutant constitutively active Gq or G11 can be targeted by FR900359 (FR) or YM-254890, which are bioavailable, selective inhibitors of the Gq/11/14 subfamily of heterotrimeric G proteins. Here, we have addressed the therapeutic potential of FR for UM. We found that FR inhibited all oncogenic Gq/11 mutants reported in UM. FR arrested growth of all Gq/11-driven UM cell lines tested, but induced apoptosis only in a few. Similarly, FR inhibited growth of, but did not efficiently kill, UM tumor cells from biopsies of primary or metastatic tumors. FR evoked melanocytic redifferentiation of UM tumor cells with low (class 1), but not high (class 2), metastatic potential. FR administered systemically below its LD50 strongly inhibited growth of PDX-derived class 1 and class 2 UM tumors in mouse xenograft models and reduced blood pressure transiently. FR did not regress xenografted UM tumors or significantly affect heart rate, liver function, hematopoiesis, or behavior. These results indicated the existence of a therapeutic window in which FR can be explored for treating UM and potentially other diseases caused by constitutively active Gq/11