Receptor-interacting protein kinase 3 (RIPK3)-mediated necroptosis is thought to be the pathophysiologically predominant pathway that leads to regulated necrosis of parenchymal cells in ischemia-reperfusion injury (IRI), and loss of either Fas-associated protein with death domain (FADD) or caspase-8 is known to sensitize tissues to undergo spontaneous necroptosis. Here, we demonstrate that renal tubules do not undergo sensitization to necroptosis upon genetic ablation of either FADD or caspase-8 and that the RIPK1 inhibitor necrostatin-1 (Nec-1) does not protect freshly isolated tubules from hypoxic injury. In contrast, irondependent ferroptosis directly causes synchronized necrosis of renal tubules, as demonstrated by intravital microscopy in models of IRI and oxalate crystal-induced acute kidney injury. To suppress ferroptosis in vivo, we generated a novel third-generation ferrostatin (termed 16-86), which we demonstrate to be more stable, to metabolism and plasma, and more potent, compared with the firstin-class compound ferrostatin-1 (Fer-1). Even in conditions with extraordinarily severe IRI, 16-86 exerts strong protection to an extent which has not previously allowed survival in any murine setting. In addition, 16-86 further potentiates the strong protective effect on IRI mediated by combination therapy with necrostatins and compounds that inhibit mitochondrial permeability transition. Renal tubules thus represent a tissue that is not sensitized to necroptosis by loss of FADD or caspase-8. Finally, ferroptosis mediates postischemic and toxic renal necrosis, which may be therapeutically targeted by ferrostatins and by combination therapy.

Mutations in all four known KCNQ potassium channel alpha-subunit genes lead to human diseases. KCNQ1 (KvLQT1) interacts with the beta-subunit KCNE1 (IsK, minK) to form the slow, depolarization-activated potassium current I(Ks) that is affected in some forms of cardiac arrhythmia. Here we show that the novel beta-subunit KCNE3 markedly changes KCNQ1 properties to yield currents that are nearly instantaneous and depend linearly on voltage. It also suppresses the currents of KCNQ4 and HERG potassium channels. In the intestine, KCNQ1 and KCNE3 messenger RNAs colocalized in crypt cells. This localization and the pharmacology, voltage-dependence and stimulation by cyclic AMP of KCNQ1/KCNE3 currents indicate that these proteins may assemble to form the potassium channel that is important for cyclic AMP-stimulated intestinal chloride secretion and that is involved in secretory diarrhoea and cystic fibrosis.

Abstract. Future ocean acidification has the potential to adversely affect many marine organisms. A growing body of evidence suggests that many species could suffer from reduced fertilization success, decreases in larval-and adult growth rates, reduced calcification rates, and even mortality when being exposed to near-future levels (year 2100 scenarios) of ocean acidification. Little research focus is currently placed on those organisms/taxa that might be less vulnerable to the anticipated changes in ocean chemistry; this is unfortunate, as the comparison of more vulnerable to more tolerant physiotypes could provide us with those physiological traits that are crucial for ecological success in a future ocean. Here, we attempt to summarize some ontogenetic and lifestyle traits that lead to an increased tolerance towards high environmental pCO 2 . In general, marine ectothermic metazoans with an extensive extracellular fluid volume may be less vulnerable to future acidification as their cells are already exposed to much higher pCO 2 values (0.1 to 0.4 kPa, ca. 1000 to 3900 µatm) than those of unicellular organisms and gametes, for which the ocean (0.04 kPa, ca. 400 µatm) is the extracellular space. A doubling in environmental pCO 2 therefore only represents a 10% change in extracellular pCO 2 in some marine teleosts. High extracellular pCO 2 values are to some degree related to high metabolic rates, as diffusion gradients need to be high in order to excrete an amount of CO 2 that is directly proportional to the amount of O 2 consumed. In active metazoans, such as teleost fish, cephalopods and Correspondence to: F. Melzner (fmelzner@ifm-geomar.de) many brachyuran crustaceans, exercise induced increases in metabolic rate require an efficient ion-regulatory machinery for CO 2 excretion and acid-base regulation, especially when anaerobic metabolism is involved and metabolic protons leak into the extracellular space. These ion-transport systems, which are located in highly developed gill epithelia, form the basis for efficient compensation of pH disturbances during exposure to elevated environmental pCO 2 . Compensation of extracellular acid-base status in turn may be important in avoiding metabolic depression. So far, maintained "performance" at higher seawater pCO 2 (>0.3 to 0.6 kPa) has only been observed in adults/juveniles of active, high metabolic species with a powerful ion regulatory apparatus. However, while some of these taxa are adapted to cope with elevated pCO 2 during their regular embryonic development, gametes, zygotes and early embryonic stages, which lack specialized ion-regulatory epithelia, may be the true bottleneck for ecological success -even of the more tolerant taxa.Our current understanding of which marine animal taxa will be affected adversely in their physiological and ecological fitness by projected scenarios of anthropogenic ocean acidification is quite incomplete. While a growing amount of empirical evidence from CO 2 perturbation experiments suggests that several taxa might react quite se...

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Mineralocorticoid receptor (MR)-deficient mice were generated by gene targeting. These animals had a normal prenatal development. During the first week of life, MR-deficient (؊͞؊) mice developed symptoms of pseudohypoaldosteronism. They finally lost weight and eventually died at around day 10 after birth from dehydration by renal sodium and water loss. At day 8, ؊͞؊ mice showed hyperkalemia, hyponatremia, and a strong increase in renin, angiotensin II, and aldosterone plasma concentrations. Methods were established to measure renal clearance and colonic transepithelial Na ؉ reabsorption in 8-day-old mice in vivo. The fractional renal Na ؉ excretion was elevated >8-fold. The glomerular filtration rate in ؊͞؊ mice was not different from controls. The effect of amiloride on renal Na ؉ excretion and colonic transepithelial voltage reflects the function of amiloide-sensitive epithelial Na ؉ channels (ENaC). In ؊͞؊ mice, it was reduced to 24% in the kidney and to 16% in the colon. There was, however, still significant residual ENaC-mediated Na ؉ reabsorption in both epithelia. RNase protection analysis of the subunits of ENaC and (Na ؉ ؉ K ؉ )-ATPase did not reveal a decrease in ؊͞؊ mice. The present data indicate that MR-deficient neonates die because they are not able to compensate renal Na ؉ loss. Regulation of Na ؉ reabsorption via MR is not achieved by transcriptional control of ENaC and (Na ؉ ؉ K ؉ )-ATPase in RNA abundance but by transcriptional control of other as yet unidentified genes. MR knockout mice will be a suitable tool for the search of these genes.