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Carnosinase 1 (CN1) contributes to diabetic nephropathy by cleaving histidine-dipeptides which scavenge reactive oxygen and carbonyl species and increase nitric oxide (NO) production. In diabetic mice renal CN1 activity is increased, the regulatory mechanisms are unknown. We therefore analysed the in vitro and in vivo regulation of CN1 activity using recombinant and human CN1, and the db/db mouse model of diabetes. Glucose, leptin and insulin did not modify recombinant and human CN1 activity in vitro, glucose did not alter renal CN1 activity of WT or db/db mice ex vivo. Reactive metabolite methylglyoxal and Fenton reagent carbonylated recombinant CN1 and doubled CN1 efficiency. NO S-nitrosylated CN1 and decreased CN1 efficiency for carnosine by 70 % (p < 0.01), but not for anserine. Both CN1 cysteine residues were nitrosylated, the cysteine at position 102 but not at position 229 regulated CN1 activities. In db/db mice, renal CN1 mRNA and protein levels were similar as in non-diabetic controls, CN1 efficiency 1.9 and 1.6 fold higher for carnosine and anserine. Renal carbonyl stress was strongly increased and NO production halved, CN1 highly carbonylated and less S-nitrosylated compared to WT mice. GSH and NO2/3 concentrations were reduced and inversely related with carnosine degradation rate (r = -0.82/-0.85). Thus, reactive metabolites of diabetes upregulate CN1 activity by post-translational modifications, and thus decrease the availability of reactive metabolite-scavenging histidine dipeptides in the kidney in a positive feedback loop. Interference with this vicious circle may represent a new therapeutic target for mitigation of DN.

Background:N-chlorotaurine (NCT), a long-lived oxidant produced by human leukocytes, can be synthesized chemically and used topically as a well-tolerated antiseptic to different body regions including sensitive ones. The aim of this study was to test the tolerability of inhaled 1% NCT in aqueous solution upon repeated application.Methods:The study was performed double-blind and randomized with a parallel test group (1% NCT) and control group (0.9% NaCl as placebo). There were two Austrian centres involved, the hospitals, Natters and Vöcklabruck. Healthy, full age volunteers were included, 12 in each centre. A total of 12 patients were treated with NCT, and 12 with placebo, exactly half of each group from each centre. The single dose was 1.2 ml inhaled over a period of 10 min using an AKITA JET nebulizer. One inhalation was done every day for five consecutive days. The primary criterion of evaluation was the forced expiratory volume in 1 second (FEV1). Secondary criteria were subjective sensations, further lung function parameters such as airway resistance, physical examination, and blood analyses (gases, electrolytes, organ function values, pharmacokinetic parameters taurine and methionine, immune parameters).Results:All included 15 females and 9 males completed the treatment and the control examinations according to the study protocol. FEV1 (100.83% ± 8.04% for NCT and 92.92% ± 11.35% for controls) remained unchanged and constant during the treatment and in control examinations 1 week and 3 months after the treatment (98.75% ± 7.37% for NCT and 91.17% ± 9.46% for controls, p > 0.082 between time points within each group). The same was true for all other objective parameters. Subjective mild sensations with a higher frequency in the test group were chlorine taste (p < 0.01) and occasional tickle in the throat (p = 0.057). Taurine and methionine plasma concentrations did not change within 60 min after inhalation or later on.Conclusions:Inhaled NCT is well tolerated as in other applications of different body regions. Side effects are mild, topical and transitory. The study was registered prospectively in the European Clinical Trials Database of the European Medicines Agency. The EudraCT number is 2012-003700-12.

The Smith-Lemli-Opitz syndrome (SLOS [MIM 270400]) is an autosomal recessive malformation syndrome that shows a great variability with regard to severity. SLOS is caused by mutations in the D7sterol-reductase gene (DHCR7), which disrupt cholesterol biosynthesis. Phenotypic variability of the disease is already known to be associated with maternal apolipoprotein E (ApoE) genotype. The aim of this study was to detect additional modifiers of the SLOS phenotype. We examined the association of SLOS severity with variants in the genes for ApoC-III, lecithin-cholesterol acyltransferase, cholesteryl-ester transfer protein, ATP-binding cassette transporter A1 (ABCA1), and methylene tetrahydrofolate reductase. Our study group included 59 SLOS patients, their mothers, and 49 of their fathers. In addition, we investigated whether ApoE and ABCA1 genotypes are associated with the viability of severe SLOS cases (n ¼ 21) caused by two null mutations in the DHCR7 gene. Maternal ABCA1 genotypes show a highly significant correlation with clinical severity in SLOS patients (P ¼ 0.007). The rare maternal p.1587Lys allele in the ABCA1 gene was associated with milder phenotypes. ANOVA analysis demonstrated an association of maternal ABCA1 genotypes with severity scores (logarithmised) of SLOS patients of P ¼ 0.004. Maternal ABCA1 explains 15.4% (R 2 ) of severity of SLOS patients. There was no association between maternal ApoE genotype and survival of the SLOS fetus carrying two null mutations. Regarding ABCA1 p.Arg1587Lys in mothers of latter SLOS cases, a significant deviation from HardyWeinberg equilibrium (HWE) was observed (P ¼ 0.005). ABCA1 is an additional genetic modifier in SLOS. Modifying placental cholesterol transfer pathways may be an approach for prenatal therapy of SLOS.