Of the vertebrate senses, touch is the least understood at the molecular level The ion channels that form the core of the mechanosensory complex and confer touch sensitivity remain unknown. However, the similarity of the brain sodium channel 1 (BNC1) to nematode proteins involved in mechanotransduction indicated that it might be a part of such a mechanosensor. Here we show that disrupting the mouse BNC1 gene markedly reduces the sensitivity of a specific component of mechanosensation: low-threshold rapidly adapting mechanoreceptors. In rodent hairy skin these mechanoreceptors are excited by hair movement. Consistent with this function, we found BNC1 in the lanceolate nerve endings that lie adjacent to and surround the hair follicle. Although BNC1 has been proposed to have a role in pH sensing, the acid-evoked current in cultured sensory neurons and the response of acid-stimulated nociceptors were normal in BNC1 null mice. These data identify the BNC1 channel as essential for the normal detection of light touch and indicate that BNC1 may be a central component of a mechanosensory complex.

Baroreceptor nerve endings detect acute fluctuations in arterial pressure. We tested the hypothesis that members of the DEG/ENaC family of cation channels, which are responsible for touch sensation in Caenorhabditis elegans, may be components of the baroreceptor mechanosensor. We found the gamma subunit of ENaC localized to the site of mechanotransduction in baroreceptor nerve terminals innervating the aortic arch and carotid sinus. A functional role for DEG/ENaC members was suggested by blockade of baroreceptor nerve activity and baroreflex control of blood pressure by an amiloride analog that inhibits DEG/ENaC channels. These data suggest that ENaC subunits may be components of the baroreceptor mechanotransducer and pave the way to a better definition of mechanisms responsible for blood pressure regulation and hypertension.

(VSMCs) to contract in response to increases in intraluminal pressure. Although mechanosensitive ion channels are thought to initiate VSMC stretch-induced contraction, their molecular identity is unknown. Recent reports suggest degenerin/epithelial Na ϩ channels (DEG/ENaC) may form mechanotransducers in sensory neurons and VSMCs; however, the role of DEG/ENaC proteins in myogenic constriction of mouse renal arteries has not been established. To test the hypothesis that DEG/ ENaC proteins are required for myogenic constriction in renal vessels, we first determined expression of ENaC transcripts and proteins in mouse renal VSMCs. Then, we determined pressure-and agonistinduced constriction and changes in vascular smooth muscle cytosolic Ca 2ϩ and Na ϩ in isolated mouse renal interlobar arteries following DEG/ENaC inhibition with amiloride and benzamil. We detect ␣-, ␤-, and ␥ENaC transcript and protein expression in cultured mouse renal VSMC. In contrast, we detect only ␤-and ␥-but not ␣ENaC protein in freshly dispersed mrVMSC. Selective DEG/ENaC inhibition, with low doses of amiloride and benzamil, abolishes pressure-induced constriction and increases in cytosolic Ca 2ϩ and Na ϩ without diminishing agonist-induced responses in isolated mouse interlobar arteries. Our findings indicate that DEG/ENaC proteins are required for myogenic constriction in mouse interlobar arteries and are consistent with our hypothesis that DEG/ENaC proteins may be components of mechanosensitive ion channel complexes required for myogenic vasoconstriction. mechanotransduction; renal blood flow autoregulation; amiloride; benzamil; isolated renal vessel; stretch-activated cation channel; calcium; sodium MYOGENIC VASOCONSTRICTION is an intrinsic property of most resistance vessels characterized by a decrease in luminal diameter in response to an increase in intraluminal pressure. The response is important in establishing basal vascular tone and maintaining blood flow autoregulation. It is well established that vascular smooth muscle (VSM) membrane depolarization and subsequent Ca 2ϩ influx via voltage-gated Ca 2ϩ channels mediate myogenic constriction (23,32,36). However, the mechanism that transduces mechanical stimuli (pressure-induced stretch) into a cellular event (depolarization) is less understood. Although mechanosensitive nonselective cation channels are thought to initiate pressure-induced depolarization (9,29,38,46), the molecule(s) involved has not been identified.Members of the degenerin/epithelial Na ϩ channel (DEG/ ENaC) family have recently been identified as mechanosensors in a variety of species and cell types (2,17,20,28,33). In mammals, DEG/ENaC proteins are found at several important sites of mechanotransduction, including dorsal root ganglion, arterial baroreflex sensory neurons, osteoblasts, keratinocytes, and vascular smooth muscle cells (VSMCs) (5, 12-14, 18, 30, 34). Two subfamilies of proteins are expressed in mammals: ENaC and acid-sensing ion channel. Acid-sensing ion channel proteins are activated by protons ...

SUMMARY Arterial baroreceptors provide a neural sensory input that reflexly regulates the autonomic drive of the circulation. Our goal was to test the hypothesis that a member of the acid sensing ion channel (ASIC) subfamily of the DEG/ENaC superfamily is an important determinant of the arterial baroreceptor reflex. We found that aortic baroreceptor neurons in the nodose ganglia and their terminals express ASIC2. Conscious ASIC2 null mice developed hypertension, had exaggerated sympathetic and depressed parasympathetic control of the circulation, and a decreased gain of the baroreflex, all indicative of an impaired baroreceptor reflex. Multiple measures of baroreceptor activity each suggests that mechanosensitivity is diminished in ASIC2- null mice. The results define ASIC2 as an important determinant of autonomic circulatory control and of baroreceptor sensitivity. The genetic disruption of ASIC2 recapitulates the pathological dysautonomia seen in heart failure and hypertension and defines a molecular defect that may be relevant to its development.

N~tnc oxide (NO) Inhibits a variety of heme-contammg enzymes, mcludmg NO synthase and cytochrome P4501Al and 2Bl The present study exammed whether NO mhlblts the production of 20-hydroxyelcosatetraenolc acid (20-HETE) by cytochrome P4504A enzymes and whether blockade of the production of this substance contributes to the vascular effects of NO Sodium mtroprusslde (SNP, lo-', lo-", and 10m3 mol/L) reduced the productlon of 20-HETE by renal mlcrosomes incubated with arachldomc acid to 71+5%, 29t4%, and 4+2% of control, respectlvely (n=S) Slmllar results were obtained with the use of 1-propanamme, 3-(2-hydroxy-2-mtroso-1-propylhydrazmo) (n=3) To determme whether mhlbitlon of 20-HETE contributes to the vasodllatory effects of NO, the effects of dlbromo-dodecenylmethylsulfinude (DDMS), a selective mhlbltor of the formatlon of 20-HETE, on the response to SNP (lo-' to 10m3 mol/L) were examined m rat renal artenoles preconstructed with phenylephrme (n=.5) SNP increased vascular diameter m a concentrafion-dependent manner to 82t4% of control After DDMS (25 ymol/L), SNP (lo-' mol/L) increased vascular diameter by only 17+3% The effects of DDMS on the mean arterial pressure (MAP) and renal blood flow (RBF) responses to mfuslon of an NO donor and a synthase mhibltor were also examined m thlobutabarbltal-anesthetrzed, Sprague-Dawley rats Infusion of MAHMA NONOate at 1, 3, 5, and 10 nmol/mm reduced MAP by 16+2, 3023,40t5, and 48?5 mm Hg and lowered renal vascular resistance (RVR) by 15+3%, 26?2%, 30?3%, and 34?4% of control After DDMS (10 mg/kg, n=7 rats), the MAP and RVR responses to I-hexamme, 6-(2-hydroxy-1 -methyl-2-mtrohydrazmo)N-methyl (MAHMA NONOate) averaged only 20% of those seen durmg control In other expenments, MAP Increased by 3224% and RBF fell to 56+5% of control after admmlstratlon of N-mtro-L-argmme (L-NArg) (10 mg/kg IV) After DDMS (10 mg/kg, n=7 rats), MAP Increased by only 19+4% and RBF fell by only 724% after L-NArg These results indicate that NO mhlblts cytochrome P4504A enzymes and that mhlbltlon of the production of 20-HETE contributes to the vasodllatory effects of NO (Hypertension. 1997;29[part 2]:320-325.)Key Words l mtnc oxide l vasculature l enzymes R ecent studies have mdlcated that the effects of many renal vasodllators are dependent on the release of NO from the endothehum Blockade of NO synthesis increases arterial pressure, decreases RBF, and potentiates tubuloglomerular feedback responses. 1 These results indicate that tonic release of NO plays an important modulatory role m the regulation of both renal and penpheral vascular tone. It 1s generally assumed that the vasodllatory effects of NO are mediated by cGMP secondary to shmulatlon of guanylyl cyclase 2.3 This concluslon 1s based on the observations that endothehum-dependent vasodilators and NO donors increase cGMP m vascular tissue and that methylene blue and other mhlbltors of guanylyl cyclase m many vessels can elm-nnate the vasodilatory response However, this generalized scheme for NO-induced vasodllatlon has been questioned ...

Non-alcoholic fatty liver disease is the most rapidly growing form of liver disease and if left untreated can result in non-alcoholic steatohepatitis, ultimately resulting in liver cirrhosis and failure. Biliverdin reductase A (BVRA) is a multifunctioning protein primarily responsible for the reduction of biliverdin to bilirubin. Also, BVRA functions as a kinase and transcription factor, regulating several cellular functions. We report here that liver BVRA protects against hepatic steatosis by inhibiting glycogen synthase kinase 3β (GSK3β) by enhancing serine 9 phosphorylation, which inhibits its activity. We show that GSK3β phosphorylates serine 73 (Ser(P)) of the peroxisome proliferator-activated receptor α (PPARα), which in turn increased ubiquitination and protein turnover, as well as decreased activity. Interestingly, liver-specific BVRA KO mice had increased GSK3β activity and Ser(P) of PPARα, which resulted in decreased PPARα protein and activity. Furthermore, the liver-specific BVRA KO mice exhibited increased plasma glucose and insulin levels and decreased glycogen storage, which may be due to the manifestation of hepatic steatosis observed in the mice. These findings reveal a novel BVRA-GSKβ-PPARα axis that regulates hepatic lipid metabolism and may provide unique targets for the treatment of non-alcoholic fatty liver disease.

Abstract-Chronic inflammation has been implicated in the pathology of hypertension; however, the role for specific cytokines remains unclear. We tested whether tumor necrosis factor-␣ blockade with etanercept (Etan) reduces mean arterial pressure in a female mouse model of systemic lupus erythematosus (SLE). SLE is a chronic inflammatory disorder with prevalent hypertension. and lowered in Etan-treated SLE mice (6645Ϯ490). Renal cortex nuclear factor B (phosphorylated and nonphosphorylated) was increased in SLE mice compared with controls and lower in Etan-treated SLE mice. These data suggest that TNF-␣ mechanistically contributes to the development of hypertension in a chronic inflammatory disease through increased renal nuclear factor B, oxidative stress, and inflammation. (Hypertension. 2010;56:643-649.) Key Words: systemic lupus erythematosus Ⅲ hypertension Ⅲ inflammation Ⅲ TNF-␣ Ⅲ oxidative stress Ⅲ cytokine A growing body of literature suggests that chronic inflammation plays an important role in the progression of several forms of hypertension. Plasma levels of inflammatory cytokines, such as tumor necrosis factor-␣ (TNF-␣) and interleukin 6, directly correlate with blood pressure and essential hypertension in humans. 1,2 In addition, recent studies demonstrate that immunosuppressive therapy with mycophenolate mofetil reduced blood pressure in essential hypertensive patients 3 and in experimental animal models of hypertension. 4 The potential mechanistic role of specific inflammatory cytokines, such as TNF-␣, in the development of hypertension remains unclear. For example, the effect of TNF-␣ blockade in experimental models of hypertension varies, ranging from having no effect on pressure 5,6 to delaying the progression 7 or even completely ameliorating hypertension. 8 Therefore, further studies to understand the contribution of this master immune regulator to the development of hypertension are warranted.Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disorder of unknown etiology that predominantly affects young women. A loss of immunologic tolerance during SLE leads to the production of autoantibodies, of which antidouble-stranded DNA (dsDNA) is the most common and is specific for the disease. Autoantibody production facilitates the formation of immune complexes that deposit in tissues and promote local inflammation and injury, with the kidneys being most commonly affected. Numerous inflammatory cytokines are implicated in the pathophysiology of SLE, including TNF-␣. 9,10 TNF-␣ expression is increased in kidney biopsies, 11 and the prevalence of hypertension is elevated in patients with SLE, reaching as high as 75%, depending on the cohort. [12][13][14][15] These data suggest that SLE may be an important disease model to examine the mechanistic role of renal TNF-␣ in the development of hypertension.In the present study, we hypothesize that TNF-␣ is an important mediator of hypertension during the chronic in-

The epithelial Na ؉ channel (ENaC) is composed of three homologous subunits: ␣, ␤ and ␥. We used gene targeting to disrupt the ␤ subunit gene of ENaC in mice. The ␤ENaC-deficient mice showed normal prenatal development but died within 2 days after birth, most likely of hyperkalemia. In the ؊͞؊ mice, we found an increased urine Na ؉ concentration despite hyponatremia and a decreased urine K ؉ concentration despite hyperkalemia. Moreover, serum aldosterone levels were increased. In contrast to ␣ENaC-deficient mice, which die because of defective lung liquid clearance, neonatal ␤ENaC deficient mice did not die of respiratory failure and showed only a small increase in wet lung weight that had little, if any, adverse physiologic consequence. The results indicate that, in vivo, the ␤ subunit is required for ENaC function in the renal collecting duct, but, in contrast to the ␣ subunit, the ␤ subunit is not required for the transition from a liquid-filled to an air-filled lung. The phenotype of the ␤ENaC-deficient mice is similar to that of humans with pseudohypoaldosteronism type 1 and may provide a useful model to study the pathogenesis and treatment of this disorder.