Mononuclear phagocytes orchestrate prolyl hydroxylase inhibition-mediated renoprotection in chronic tubulointerstitial nephritis.

Prolyl hydroxylase domain enzyme inhibitors (PHDIs) stabilize hypoxia-inducible factors (HIFs), and are protective in models of acute ischemic and inflammatory kidney disease. Whether PHDIs also confer protection in chronic inflammatory kidney disease models remains unknown. Here we investigated long-term effects of PHDI treatment in adenine-induced nephropathy as a model for chronic tubulointerstitial nephritis. After three weeks, renal dysfunction and tubulointerstitial damage, including proximal and distal tubular injury, tubular dilation and renal crystal deposition were significantly attenuated in PHDI-treated (the isoquinoline derivative ICA and Roxadustat) compared to vehicle-treated mice with adenine-induced nephropathy. Crystal-induced renal fibrosis was only partially diminished by treatment with ICA. Renoprotective effects of ICA treatment could not be attributed to changes in adenine metabolism or urinary excretion of the metabolite 2,8-dihydroxyadenine. ICA treatment reduced inflammatory infiltrates of F4/80+ mononuclear phagocytes in the kidneys and supported a regulatory, anti-inflammatory immune response. Furthermore, interstitial deposition of complement C1q was decreased in ICA-treated mice fed an adenine-enriched diet. Tubular cell-specific HIF-1α and myeloid cell-specific HIF-1α and HIF-2α expression were not required for the renoprotective effects of ICA. In contrast, depletion of mononuclear phagocytes with clodronate largely abolished the nephroprotective effects of PHD inhibition. Thus, our findings indicate novel and potent systemic anti-inflammatory properties of PHDIs that confer preservation of kidney function and structure in chronic tubulointerstitial inflammation and might counteract kidney disease progression.

Safety of ipsilesional anodal transcranial direct current stimulation in acute photothrombotic stroke: implications for early neurorehabilitation.

Early rehabilitation in the acute phase of stroke, that bears unique neuroplastic properties, is the current standard to reduce disability. Anodal transcranial direct current stimulation can augment neurorehabilitation in chronic stroke. Studies in the acute phase are sparse and held back by inconclusive preclinical data pointing towards potential negative interaction of the excitability increasing tDCS modality with stroke-induced glutamate toxicity. In this present study, we aimed to evaluate structural and behavioral safety of anodal tDCS applied in the acute phase of stroke. Photothrombotic stroke including the right primary motor cortex was induced in rats. 24 h after stroke anodal tDCS was applied for 20 min ipsilesionally at one of four different current densities in freely moving animals. Effects on the infarct volume and on stroke induced neuroinflammation were assessed. Behavioral consequences were monitored. Infarct volume and the modified Neurological Severity Score were not affected by anodal tDCS. Pasta handling, a more sensitive task for sensorimotor deficits, and microglia reactivity indicated potentially harmful effects at the highest tDCS current density tested (47.8 A/m2), which is more than 60 times higher than intensities commonly used in humans. Compared to published safety limits of anodal tDCS in healthy rats, recent stroke does not increase the sensitivity of the brain to anodal tDCS, as assessed by lesion size and neuroinflammatory response. Behavioral deficits only occurred at the highest intensity, which was associated with increased neuroinflammation. When safety limits of commonly used clinical tDCS are met, augmentation of early neurorehabilitation after stroke by anodal tDCS appears to be feasible.

A Fluorescent Benzo[g]isoquinoline-Based HIF Prolyl Hydroxylase Inhibitor for Cellular Imaging.

Prolyl hydroxylation domain (PHD) enzymes catalyze the hydroxylation of the transcription factor hypoxia-inducible factor (HIF) and serve as cellular oxygen sensors. HIF and the PHD enzymes regulate numerous potentially tissue-protective target genes which can adapt cells to metabolic and ischemic stress. We describe a fluorescent PHD inhibitor (1-chloro-4-hydroxybenzo[g]isoquinoline-3-carbonyl)glycine which is suited to fluorescence-based detection assays and for monitoring PHD inhibitors in biological systems. In cell-based assays, application of the fluorescent PHD inhibitor allowed co-localization with a cellular PHD enzyme and led to live cell imaging of processes involved in cellular oxygen sensing.