Renal epithelial cells release ATP constitutively under basal conditions and release higher quantities of purine nucleotide in response to stimuli. ATP filtered at the glomerulus, secreted by epithelial cells along the nephron, and released serosally by macula densa cells for feedback signaling to afferent arterioles within the glomerulus has important physiological signaling roles within kidneys. In autosomal recessive polycystic kidney disease (ARPKD) mice and humans, collecting duct epithelial cells lack an apical central cilium or express dysfunctional proteins within that monocilium. Collecting duct principal cells derived from an Oak Ridge polycystic kidney (orpk Tg737 ) mouse model of ARPKD lack a well-formed apical central cilium, thought to be a sensory organelle. We compared these cells grown as polarized cell monolayers on permeable supports to the same cells where the apical monocilium was genetically rescued with the wild-type Tg737 gene that encodes Polaris, a protein essential to cilia formation. Constitutive ATP release under basal conditions was low and not different in mutant versus rescued monolayers. However, genetically rescued principal cell monolayers released ATP three-to fivefold more robustly in response to ionomycin. Principal cell monolayers with fully formed apical monocilia responded three-to fivefold greater to hypotonicity than mutant monolayers lacking monocilia. In support of the idea that monocilia are sensory organelles, intentionally harsh pipetting of medium directly onto the center of the monolayer induced ATP release in genetically rescued monolayers that possessed apical monocilia. Mechanical stimulation was much less effective, however, on mutant orpk collecting duct principal cell monolayers that lacked apical central monocilia. Our data also show that an increase in cytosolic free Ca 2+ primes the ATP pool that is released in response to mechanical stimuli. It also appears that hypotonic cell swelling and mechanical pipetting stimuli trigger release of a common ATP pool. Ciliumcompetent monolayers responded to flow with an increase in cell Ca 2+ derived from both extracellular and intracellular stores. This flow-induced Ca 2+ signal was less robust in cilium-deficient monolayers. Flow-induced Ca 2+ signals in both preparations were attenuated by extracellular gadolinium and by extracellular apyrase, an ATPase/ADPase. Taken together, these data suggest that apical monocilia are sensory organelles and that their presence in the apical membrane facilitates the formation of a mature ATP secretion apparatus responsive to chemical, osmotic, and mechanical stimuli. The cilium and autocrine ATP signaling appear to work in concert to control cell Ca 2+ . Loss of a cilium-dedicated autocrine purinergic signaling system may be a critical underlying etiology for ARPKD and may lead to disinhibition and/or upregulation of multiple sodium (Na + ) absorptive mechanisms and a resultant severe hypertensive phenotype in ARPKD and, possibly, other diseases.Purinergic Signalling (...

We sought to present the epidemiology of intentional burns, both deliberate self-inflicted burns and assault burns. Patient records from the University of Alabama at Birmingham Burn Center were reviewed retrospectively. Information pertaining to demographic and injury characteristics were obtained. Ninety-six patients with intentional burns were identified. Patients sustaining intentional burn injury had larger mean TBSA burned (26.1% vs 13.8%), longer mean hospital length of stay (19.9 days vs 13.2 days), higher incidence of inhalational injury (20.8% vs 8.7%), higher rate of mortality (20.0% vs 9.8%), and were more likely to have an elevated blood alcohol content (14.6% vs 7%) when compared with all other burn patients. Patients with deliberate self-burns were more likely to be men (85.7% vs 55.7%) and more likely to have a positive drug screen test than assault burn patients (11.4% vs 0%). Patients who suffer intentional burns tend to have more severe burns and experience worse outcomes.

The nephron is the functional unit of the kidney. Blood and plasma are continually filtered within the glomeruli that begin each nephron. Adenosine 5′ triphosphate (ATP) and its metabolites are freely filtered by each glomerulus and enter the lumen of each nephron beginning at the proximal convoluted tubule (PCT). Flow rate, osmolality, and other mechanical or chemical stimuli for ATP secretion are present in each nephron segment. These ATP-release stimuli are also different in each nephron segment due to water or salt permeability or impermeability along different luminal membranes of the cells that line each nephron segment. Each of the above stimuli can trigger additional ATP release into the lumen of a nephron segment. Each nephron-lining epithelial cell is a potential source of secreted ATP. Together with filtered ATP and its metabolites derived from the glomerulus, secreted ATP and adenosine derived from cells along the nephron are likely the principal two of several nucleotide and nucleoside candidates for renal autocrine and paracrine ligands within the tubular fluid of the nephron. This minireview discusses the first principles of purinergic signaling as they relate to the nephron and the urinary bladder. The review discusses how the lumen of a renal tubule presents an ideal purinergic signaling microenvironment. The review also illustrates how remodeled and encapsulated cysts in autosomal dominant polycystic kidney disease (ADPKD) and remodeled pseudocysts in autosomal recessive PKD (ARPKD) of the renal collecting duct likely create an even more ideal microenvironment for purinergic signaling. Once trapped in these closed microenvironments, purinergic signaling becomes chronic and likely plays a significant epigenetic and detrimental role in the secondary progression of PKD, once the remodeling of the renal tissue has begun. In PKD cystic microenvironments, we argue that normal purinergic signaling within the lumen of the nephron provides detrimental acceleration of ADPKD once remodeling is complete.

Dietary sodium chloride (salt) has long been considered injurious to the kidney by promoting the development of glomerular and tubulointerstitial fibrosis. Endothelial cells throughout the vasculature and glomeruli respond to increased dietary salt intake with increased production of transforming growth factor beta (TGF-β) and nitric oxide (NO). High-salt intake activates large conductance, voltage- and calcium-activated potassium channels (BKCa) channels in endothelial cells. Activation of BKCa channels promotes signaling through proline-rich tyrosine kinase-2 (Pyk2), c-Src, Akt, and mitogen-activated protein kinase (MAPK) pathways that lead to endothelial production of TGF-β and NO. TGF-β signaling is broadly accepted as a strong stimulator of renal fibrosis. The classic description of TGF-β signaling pathology in renal disease involves signaling through Smad proteins resulting in extracellular matrix (ECM) deposition and fibrosis. Active TGF-β1 also causes fibrosis by inducing epithelial-mesenchymal transition (EMT) and apoptosis. By enhancing TGF-β signaling, increased dietary salt intake leads to progressive renal failure from nephron loss and glomerular and tubulointerstitial fibrosis.

Transforming growth factor (TGF)-β plays a central role in vascular homeostasis and in the pathology of vascular disease. There is a growing appreciation for the role of nitric oxide (NO) and carbon monoxide (CO) as highly diffusible, bioactive signaling molecules in the vasculature. We hypothesized that both NO and CO increase endocytosis of TGF-β receptor type 1 (TβR1) in vascular smooth muscle cells (VSMCs) through activation of dynamin-2, shielding cells from the effects of circulating TGF-β. In this study, primary cultures of VSMCs from Sprague-Dawley rats were treated with NO-releasing molecule 3 (a NO chemical donor), CO-releasing molecule 2 (a CO chemical donor), or control. NO and CO stimulated dynamin-2 activation in VSMCs. NO and CO promoted time- and dose-dependent endocytosis of TβR1. By decreasing TβR1 surface expression through this dynamin-2-dependent process, NO and CO diminished the effects of TGF-β on VSMCs. These findings help explain an important mechanism by which NO and CO signal in the vasculature by decreasing surface expression of TβR1 and the cellular response to TGF-β.