Early responsiveness to continuous erythropoietin receptor activator predicts renal prognosis and is determined by a novel antioxidative marker in non-dialysis chronic kidney disease: a prospective, observational, single-center study.

BACKGROUND: Responsiveness to erythropoietin-stimulating agents (ESAs) is important for anemia management in chronic kidney disease (CKD). We assessed the effects of a continuous erythropoietin receptor activator (CERA) on renoprotection beyond anemia management and the correlation between the responsiveness to ESAs and oxidative stress markers in CKD. METHODS: This single-center, prospective, observational study was conducted over 24 months. We administered CERA to 35 non-dialysis patients with hemoglobin (Hb) < 11 g/dL and examined the results of the serum diacron-reactive oxygen metabolite (dROMs) test for oxidative stress markers and biological antioxidant potential (BAP) test for antioxidant markers. We then examined the renoprotective effects of CERA and the responsiveness to CERA. RESULTS: Eighteen patients experienced renal events (doubling of serum creatinine levels, decreased estimated glomerular filtration rate to < 6.0 mL/min/1.73 m2, or initiation of renal replacement therapy), seventeen of which survived. Kaplan-Meier analysis showed that responsiveness to CERA during the initial 3-month treatment period was a good predictor of renal events. Moreover, a high response to CERA during the 3 months independently suppressed renal events (hazard ratio, 0.344). High BAP levels at baseline were significantly associated with high responsiveness to CERA during the initial 3-month treatment period. CONCLUSION: Responsiveness to CERA during the first 3 months was an important indicator of CKD progression. Moreover, BAP test results determined responsiveness to CERA. This is the first report to show how antioxidant levels can be a potential marker of CERA's ability to control anemia in CKD patients.

Formation of M-Like Intermediates in Proteorhodopsin in Alkali Solutions (pH ≥ ∼8.5) Where the Proton Release Occurs First in Contrast to the Sequence at Lower pH.

Proteorhodopsin (PR) is an outward light-driven proton pump observed in marine eubacteria. Despite many structural and functional similarities to bacteriorhodopsin (BR) in archaea, which also acts as an outward proton pump, the mechanism of the photoinduced proton release and uptake is different between two H(+)-pumps. In this study, we investigated the pH dependence of the photocycle and proton transfer in PR reconstituted with the phospholipid membrane under alkaline conditions. Under these conditions, as the medium pH increased, a blue-shifted photoproduct (defined as Ma), which is different from M, with a pKa of ca. 9.2 was produced. The sequence of the photoinduced proton uptake and release during the photocycle was inverted with the increase in pH. A pKa value of ca. 9.5 was estimated for this inversion and was in good agreement with the pKa value of the formation of Ma (∼ 9.2). In addition, we measured the photoelectric current generated by PRs attached to a thin polymer film at varying pH. Interestingly, increases in the medium pH evoked bidirectional photocurrents, which may imply a possible reversal of the direction of the proton movement at alkaline pH. On the basis of these findings, a putative photocycle and proton transfer scheme in PR under alkaline pH conditions was proposed.