d'Uscio, Livius V

Abstract Aim We aimed to test the hypothesis that a high‐salt diet (HS) impairs NO signaling in kidney microvascular endothelial cells through a histone deacetylase 1 (HDAC1)‐dependent mechanism. Methods Male Sprague Dawley rats were fed normal salt diet (NS; 0.49% NaCl) or HS (4% NaCl) for 2 weeks. NO signaling was assessed by measuring L‐NAME induced vasoconstriction of the afferent arteriole using the blood perfused juxtamedullary nephron (JMN) preparation. In this preparation, kidneys were perfused with blood from a donor rat on a matching or different diet to that of the kidney donor. Kidney endothelial cells were isolated with magnetic activated cell sorting and HDAC1 activity was measured. Results We found HS‐induced impaired NO signaling in the afferent arteriole. This was restored by inhibition of HDAC1 with MS‐275. Consistent with these findings, HDAC1 activity was increased in kidney endothelial cells. We further found the loss of NO to be dependent upon the diet of the blood donor rather than the diet of the kidney donor and the plasma from HS‐fed rats to be sufficient to induce impaired NO signaling. This indicates the presence of a humoral factor we termed plasma‐derived endothelial dysfunction mediator (PDEM). Pretreatment with the antioxidants, PEG‐SOD and PEG‐catalase, as well as the NOS cofactor, tetrahydrobiopterin, restored NO signaling. Conclusion We conclude that HS activates endothelial HDAC1 through PDEM leading to decreased NO signaling. This study provides novel insights into the molecular mechanisms by which a HS decreases renal microvascular endothelial NO signaling.

The mechanisms underlying dysfunction of cerebral microvasculature induced by type 1 diabetes (T1D) are not fully understood. We hypothesized that in cerebral microvascular endothelium, α-processing of amyloid precursor protein (APP) is impaired by T1D. In cerebral microvessels derived from streptozotocin (STZ)-induced T1D mice protein levels of APP and its α-processing enzyme, a disintegrin and metalloprotease 10 (ADAM10) were significantly decreased, along with down-regulation of adenylate cyclase 3 (AC3) and enhanced production of thromboxane A 2 (TXA 2 ). In vitro studies in human brain microvascular endothelial cells (BMECs) revealed that knockdown of AC3 significantly suppressed ADAM10 protein levels, and that activation of TXA 2 receptor decreased APP expression. Furthermore, levels of soluble APPα (sAPPα, a product of α-processing of APP) were significantly reduced in hippocampus of T1D mice. In contrast, amyloidogenic processing of APP was not affected by T1D in both cerebral microvessels and hippocampus. Most notably, studies in endothelial specific APP knockout mice established that genetic inactivation of APP in endothelium was sufficient to significantly reduce sAPPα levels in the hippocampus. In aggregate, our findings suggest that T1D impairs non-amyloidogenic processing of APP in cerebral microvessels. This may exert detrimental effect on local concentration of neuroprotective molecule, sAPPα, in the hippocampus.