Control of Podocyte and Glomerular Capillary Wall Structure and Elasticity by WNK1 Kinase.

Cytoskeletal structure and its regulation are essential for maintenance of the differentiated state of specific types of cells and their adaptation to physiologic and pathophysiologic conditions. Renal glomerular capillaries, composed of podocytes, endothelial cells, and the glomerular basement membrane, have distinct structural and biophysical properties and are the site of injury in many glomerular diseases. Calcineurin inhibitors, immunosuppressant drugs used for organ transplantation and auto-immune diseases, can protect podocytes and glomerular capillaries from injury by preserving podocyte cytoskeletal structure. These drugs cause complications including hypertension and hyperkalemia which are mediated by WNK (With No Lysine) kinases as well as vasculopathy with glomerulopathy. WNK kinases and their target kinases oxidative stress-responsive kinase 1 (OSR1) and SPS1-related proline/alanine-rich kinase (SPAK) have fundamental roles in angiogenesis and are activated by calcineurin inhibitors, but the actions of these agents on kidney vasculature, and glomerular capillaries are not fully understood. We investigated WNK1 expression in cultured podocytes and isolated mouse glomerular capillaries to determine if WNK1 contributes to calcineurin inhibitor-induced preservation of podocyte and glomerular structure. WNK1 and OSR1/SPAK are expressed in podocytes, and in a pattern similar to podocyte synaptopodin in glomerular capillaries. Calcineurin inhibitors increased active OSR1/SPAK in glomerular capillaries, the Young's modulus (E) of glomeruli, and the F/G actin ratio, effects all blocked by WNK inhibition. In glomeruli, WNK inhibition caused reduced and irregular synaptopodin-staining, abnormal capillary and foot process structures, and increased deformability. In cultured podocytes, FK506 activated OSR1/SPAK, increased lamellipodia, accelerated cell migration, and promoted traction force. These actions of FK506 were reduced by depletion of WNK1. Collectively, these results demonstrate the importance of WNK1 in regulation of the podocyte actin cytoskeleton, biophysical properties of glomerular capillaries, and slit diaphragm structure, all of which are essential to normal kidney function.

A pharmacist based intervention to improve the care of patients with CKD: a pragmatic, randomized, controlled trial.

BACKGROUND: Primary care providers do not routinely follow guidelines for the care of patients with chronic kidney disease (CKD). Multidisciplinary efforts may improve care for patients with chronic disease. Pharmacist based interventions have effectively improved management of hypertension. We performed a pragmatic, randomized, controlled trial to evaluate the effect of a pharmacist based quality improvement program on 1) outcomes for patients with CKD and 2) adherence to CKD guidelines in the primary care setting. METHODS: Patients with moderate to severe CKD receiving primary care services at one of thirteen community-based Veterans Affairs outpatient clinics were randomized to a multifactorial intervention that included a phone-based pharmacist intervention, pharmacist-physician collaboration, patient education, and a CKD registry (n = 1070) or usual care (n = 1129). The primary process outcome was measurement of parathyroid hormone (PTH) during the one year study period. The primary clinical outcome was blood pressure (BP) control in subjects with poorly controlled hypertension at baseline. RESULTS: Among those with poorly controlled baseline BP, there was no difference in the last recorded BP or the percent at goal BP during the study period (42.0% vs. 41.2% in the control arm). Subjects in the intervention arm were more likely to have a PTH measured during the study period (46.9% vs. 16.1% in the control arm, P <0.001) and were on more classes of antihypertensive medications at the end of the study (P = 0.02). CONCLUSIONS: A one-time pharmacist based intervention proved feasible in patients with CKD. While the intervention did not improve BP control, it did improve guideline adherence and increased the number of antihypertensive medications prescribed to subjects with poorly controlled BP. These findings can inform the design of quality improvement programs and future studies which are needed to improve care of patients with CKD. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01290614.

Novel Ca receptor signaling pathways for control of renal ion transport.

PURPOSE OF REVIEW: A rise in extracellular Ca acting through the calcium sensing receptor (CaR) causes physiologically significant loss of Na, K, Cl, Ca, and water. The CaR is expressed in all nephron segments, but its effects on ion and water transport in specific segments as well as the mechanisms by which it regulates ion and water transport is not fully understood. This review will summarize recent information regarding the renal transport effects of the CaR. RECENT FINDINGS: Considerable progress has been made in characterizing TRPV5, the regulated Ca entry pathway in the distal convoluted tubule (DCT), but precisely how the CaR contributes to its regulation is not known. The CaR interacts with, and inactivates, a K channel, Kir4.1, in the renal distal convoluted tubule. Recently described loss-of-function mutations in this K channel lead to a complicated phenotype that includes salt wasting, suggesting that inactivation of Kir4.1 by the CaR may contribute to the salt wasting observed in response to CaR activation. SUMMARY: The CaR mediates the effects of extracellular Ca on the kidney and is an essential control point in regulation of Ca balance and possibly physiologic regulation of NaCl balance, but the circumstances for regulation of Na balance are not fully established in mammals. The thick ascending limb of Henle and the distal convoluted tubule appear to be the nephron segments most responsible for the effects of the CaR on ion and water transport, although its mechanisms of action are not fully established.