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HIV-associated nephropathy (HIVAN) impairs functions of both glomeruli and tubules. Attention has been previously focused on the HIVAN glomerulopathy. Tubular injury has drawn increased attention because sodium wasting is common in hospitalized HIV/AIDS patients. We used viral protein R (Vpr)-transgenic mice to investigate the mechanisms whereby Vpr contributes to urinary sodium wasting. In phosphoenolpyruvate carboxykinase promoter-driven Vpr-transgenic mice, in situ hybridization showed that Vpr mRNA was expressed in all nephron segments, including the distal convoluted tubule. Vpr-transgenic mice, compared with wild-type littermates, markedly increased urinary sodium excretion, despite similar plasma renin activity and aldosterone levels. Kidneys from Vpr-transgenic mice also markedly reduced protein abundance of the Na+-Cl- cotransporter (NCC), while mineralocorticoid receptor (MR) protein expression level was unchanged. In African green monkey kidney cells, Vpr abrogated the aldosterone-mediated stimulation of MR transcriptional activity. Gene expression of Slc12a3 (NCC) in Vpr-transgenic mice was significantly lower compared with wild-type mice, assessed by both qRT-PCR and RNAScope in situ hybridization analysis. Chromatin immunoprecipitation assays identified multiple MR response elements (MRE), located from 5 kb upstream of the transcription start site and extending to the third exon of the SLC12A3 gene. Mutation of MRE and SP1 sites in the SLC12A3 promoter region abrogated the transcriptional responses to aldosterone and Vpr, indicating that functional MRE and SP1 are required for the SLC12A3 gene suppression in response to Vpr. Thus, Vpr attenuates MR transcriptional activity and inhibits Slc12a3 transcription in the distal convoluted tubule and contributes to salt wasting in Vpr-transgenic mice. [ABSTRACT FROM AUTHOR]

Renal proximal tubule cells from spontaneously hypertensive rats (SHR), compared with normotensive Wistar-Kyoto rats (WKY), have increased oxidative stress. The contribution of mitochondrial oxidative phosphorylation to the subsequent hypertensive phenotype remains unclear. We found that renal proximal tubule cells from SHR, relative to WKY, had significantly higher basal oxygen consumption rates, adenosine triphosphate synthesis-linked oxygen consumption rates, and maximum and reserve respiration. These bioenergetic parameters indicated increased mitochondrial function in renal proximal tubule cells from SHR compared with WKY. Pyruvate dehydrogenase complex activity was consistently higher in both renal proximal tubule cells and cortical homogenates from SHR than those from WKY. Treatment for 6 days with dichloroacetate, an inhibitor of pyruvate dehydrogenase kinase, significantly increased renal pyruvate dehydrogenase complex activity and systolic blood pressure in 3-week-old WKY and SHR. Therefore, mitochondrial oxidative phosphorylation is higher in renal proximal tubule cells from SHR compared with WKY. Thus, the pyruvate dehydrogenase complex is a determinant of increased mitochondrial metabolism that could be a causal contributor to the hypertension in SHR. [ABSTRACT FROM AUTHOR]

The SNX-PXA-RGS-PXC subfamily of sorting nexins (SNXs) belongs to the superfamily of SNX proteins. SNXs are characterized by the presence of a common phox-homology (PX) domain, along with other functional domains that play versatile roles in cellular signaling and membrane trafficking. In addition to the PX domain, the SNX-PXA-RGS-PXC subfamily, except for SNX19, contains a unique RGS (regulators of G protein signaling) domain that serves as GTPase activating proteins (GAPs), which accelerates GTP hydrolysis on the G protein α subunit, resulting in termination of G protein-coupled receptor (GPCR) signaling. Moreover, the PX domain selectively interacts with phosphatidylinositol-3-phosphate and other phosphoinositides found in endosomal membranes, while also associating with various intracellular proteins. Although SNX19 lacks an RGS domain, all members of the SNX-PXA-RGS-PXC subfamily serve as dual regulators of receptor cargo signaling and endosomal trafficking. This review discusses the known and proposed functions of the SNX-PXA-RGS-PXC subfamily and how it participates in receptor signaling (both GPCR and non-GPCR) and endosomal-based membrane trafficking. Furthermore, we discuss the difference of this subfamily of SNXs from other subfamilies, such as SNX-BAR nexins (Bin-Amphiphysin-Rvs) that are associated with retromer or other retrieval complexes for the regulation of receptor signaling and membrane trafficking. Emerging evidence has shown that the dysregulation and malfunction of this subfamily of sorting nexins lead to various pathophysiological processes and disorders, including hypertension. [ABSTRACT FROM AUTHOR]

Poly-(ADP-ribose) polymerases (PARPs) are a protein family that make ADP-ribose modifications on target genes and proteins. PARP family members contribute to the pathogenesis of chronic inflammatory diseases, including atherosclerosis, in which monocytes/macrophages play important roles. PARP inhibition is protective against atherosclerosis. However, the mechanisms by which PARP inhibition exerts this beneficial effect are not well understood. Here we show that in THP-1 monocytes, inhibition of PARP by olaparib attenuated oxidized low-density lipoprotein (oxLDL)-induced protein expressions of nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing-3 (NLRP3) inflammasome components: NLRP3, apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC), and caspase-1. Consistent with this effect, olaparib decreased oxLDL-enhanced interleukin (IL)-1β and IL-18 protein expression. Olaparib also decreased the oxLDL-mediated increase in mitochondrial reactive oxygen species. Similar to the effects of the NLRP3 inhibitor, MCC950, olaparib attenuated oxLDL-induced adhesion of monocytes to cultured human umbilical vein endothelial cells and reduced foam cell formation. Furthermore, olaparib attenuated the oxLDL-mediated activation of nuclear factor (NF)-κB through the oxLDL-mediated increase in IκBα phosphorylation and assembly of NF-κB subunits, demonstrated by co-immunoprecipitation of IκBα with RelA/p50 and RelB/p52 subunits. Moreover, PARP inhibition decreased oxLDL-mediated protein expression of a NF-κB target gene, VCAM1, encoding vascular cell adhesion molecule-1. This finding indicates an important role for NF-κB activity in PARP-mediated activation of the NLRP3 inflammasome. Thus, PARP inhibition by olaparib attenuates NF-κB and NLRP3 inflammasome activities, lessening monocyte cell adhesion and macrophage foam cell formation. These inhibitory effects of olaparib on NLRP3 activity potentially protect against atherosclerosis. [ABSTRACT FROM AUTHOR]

Aims: Reactive oxygen species are highly reactive molecules generated in different subcellular compartments. Both the dopamine D5 receptor (D5R) and endoplasmic reticulum (ER)-resident peroxiredoxin-4 (PRDX4) play protective roles against oxidative stress. This study is aimed at investigating the interaction between PRDX4 and D5R in regulating oxidative stress in the kidney. Results: Fenoldopam (FEN), a D1R and D5R agonist, increased PRDX4 protein expression, mainly in non-lipid rafts, in D5R-HEK 293 cells. FEN increased the co-immunoprecipitation of D5R and PRDX4 and their colocalization, particularly in the ER. The efficiency of Förster resonance energy transfer was increased with FEN treatment measured with fluorescence lifetime imaging microscopy. Silencing of PRDX4 increased hydrogen peroxide production, impaired the inhibitory effect of FEN on hydrogen peroxide production, and increased the production of interleukin-1β, tumor necrosis factor (TNF), and caspase-12 in renal cells. Furthermore, in Drd5−/− mice, which are in a state of oxidative stress, renal cortical PRDX4 was decreased whereas interleukin-1β, TNF, and caspase-12 were increased, relative to their normotensive wild-type Drd5+/+ littermates. Innovation: Our findings demonstrate a novel relationship between D5R and PRDX4 and the consequent effects of this relationship in attenuating hydrogen peroxide production in the ER and the production of proinflammatory cytokines. This study provides the potential for the development of biomarkers and new therapeutics for renal inflammatory disorders, including hypertension. Conclusion: PRDX4 interacts with D5R to decrease oxidative stress and inflammation in renal cells that may have the potential for translational significance. Antioxid. Redox Signal. 38, 1150–1166. [ABSTRACT FROM AUTHOR]

Effective receptor signaling is anchored on the preferential localization of the receptor in lipid rafts, which are plasma membrane platforms replete with cholesterol and sphingolipids. We hypothesized that the dopamine D1 receptor (D1R) contains structural features that allow it to reside in lipid rafts for its activity. Mutation of C347 palmitoylation site and Y218 of a newly identified Cholesterol Recognition Amino Acid Consensus motif resulted in the exclusion of D1R from lipid rafts, blunted cAMP response, impaired sodium transport, and increased oxidative stress in renal proximal tubule cells (RPTCs). Kidney‐restricted silencing of Drd1 in C57BL/6J mice increased blood pressure (BP) that was normalized by renal tubule‐restricted rescue with D1R‐wild‐type but not the mutant D1R 347A that lacks a palmitoylation site. Kidney‐restricted disruption of lipid rafts by β‐MCD jettisoned the D1R from the brush border, decreased sodium excretion, and increased oxidative stress and BP in C57BL/6J mice. Deletion of the PX domain of the novel D1R‐binding partner sorting nexin 19 (SNX19) resulted in D1R partitioning solely to non‐raft domains, while silencing of SNX19 impaired D1R function in RPTCs. Kidney‐restricted silencing of Snx19 resulted in hypertension in C57BL/6J mice. Our results highlight the essential role of lipid rafts for effective D1R signaling. [ABSTRACT FROM AUTHOR]

R3865 --> 560.10 --> Peroxiredoxin‐4 (PRDX4), an endoplasmic reticulum (ER)‐localized antioxidant enzyme, plays an essential role in cellular redox homeostasis by reducing hydrogen peroxide from thiol‐containing compounds. The dopamine D5 Receptor (D5R) also plays a protective role against oxidative stress. We hypothesize that D5R interacts with the PRDX4 to reduce oxidative stress in the kidney. In D5R‐HEK 293 cells, fenoldopam (FEN, 25 nM/12 hr, n=4), a D1R and D5R receptor agonist, increased PRDX4 protein expression (1.92±0.12‐fold over basal level, n=4), mainly in non‐lipid raft (LR) fractions (LRs: 24.9±11.4%, non‐LRs: 75.1±11.4%, baseline; LRs: 30.9±13.9%, non‐LRs: 174.1±16.7%, FEN). By contrast, fenoldopam did not affect PRDX4 protein expression in D1R‐HEK 293 cells, indicating a D5R‐specific effect on PRDX4 protein expression. In human renal proximal tubule cells (hRPTCs) and D5R HEK293 cells, fenoldopam increased the co‐immunoprecipitation between PRDX4 and D5R and their co‐localization in the ER. SiRNA‐mediated silencing of PRDX4 increased hydrogen peroxide production in both the vehicle (Veh)‐ and fenoldopam‐treated hRPTCs [(scrambled siRNA: 100 ±15.1% and 55.2± 7.2% with Veh and FEN, respectively; PRDX4 siRNA: 161.8±15.3% and 145.1±14.6 % with Veh and FEN, respectively, n=4)]. The D5R protects against inflammation and siRNA silencing of PRDX4 increased the production of the pro‐inflammatory cytokines, interleukin‐1β [26.88±3.8 and 46.40±4.2 pg/mL (n=3, D5R‐HEK 293); 15.87±1.2 and 37.9±1.4 pg/mL (n=3, hRPTCs), and tumor necrosis factors [131.7±6.5 and 271.2±18.1 pg/mL (n=4, D5R‐HEK 293); 108.8±11.8 and 240.1±13.7 pg/mL (n=4, hRPTCs)]. In D5R‐HEK293 and hRPTCs, the fenoldopam‐mediated decrease in ER‐resident caspase‐12 was also impaired by gene silencing of PRDX4. Furthermore, PRDX4 protein expression was reduced in the kidney cortices of Drd5‐/‐ mice, relative to Drd5 WT mice (WT: 1.00±0.12, n=4; Drd5‐/‐: 0.64±0.13, n=4; P<0.05). We conclude that D5R positively interacts with PRDX4 to reduce ER stress in the kidney. [ABSTRACT FROM AUTHOR]