Munc18-1-interacting protein 3 mitigates renal fibrosis through protection of tubular epithelial cells from apoptosis.

BACKGROUND: Tubulointerstitial fibrosis is a hallmark of chronic kidney disease (CKD), and is initiated by tubular epithelial cell (TEC) injury. Hypoxia promotes tubular cell death, fibrosis and CKD progression. Munc18-1-interacting protein 3 (Mint3) is a molecule that activates hypoxia-inducible factors (HIFs) by binding and suppressing factor inhibiting HIF-1 (FIH). However, the role of Mint3 in tubulointerstitial fibrosis remains unknown. METHODS: We induced fibrosis of the kidney after unilateral ischemia-reperfusion injury (uIRI) in Mint3-knockout and littermate wild-type mice. The duration of ischemia was 23 min and the kidneys were harvested at 24 h and 7 days after ischemia-reperfusion. The function of Mint3 was further investigated by using mouse cortical tubular (MCT) cells, which were treated with Mint3 and/or FIH small interfering RNA and exposed to normoxia or hypoxia. RESULTS: Knockout of Mint3 did not affect the acute injury induced by uIRI, but exacerbated the tubulointerstitial fibrosis, accompanied by an increase in TEC apoptosis. Consistently, hypoxia-induced apoptosis of MCT cells was aggravated by Mint3 knockdown. Unexpectedly, the additional knockdown of FIH did not suppress the increase in apoptosis by Mint3 knockdown, demonstrating the irrelevance of the FIH/HIF pathway. Therefore, we next focused on nuclear factor (NF)-κB, which has an anti-apoptotic role. Indeed, not only the expression of the inhibitory NF-κB p50 but also the DNA-binding activity of p50/p50 homodimer was increased by knockdown of Mint3 in the TECs, along with the decreased expressions of the NF-κB-targeted anti-apoptotic genes. An increase in NF-κB p50 was also confirmed in Mint3-knockout kidneys. CONCLUSIONS: Mint3 in epithelial cells protects the cells from apoptosis by up-regulating anti-apoptotic effects of NF-κB, leading to fibrosis suppression. This new pathophysiology of tubulointerstitial fibrosis could be a target of future therapy for CKD.

Three cases of posterior reversible encephalopathy syndrome with chronic kidney disease triggered by infection.

Posterior reversible encephalopathy syndrome (PRES) is a clinical and radiological condition with diverse neurological manifestations. Many clinical factors are known causes of PRES, but only a few cases of PRES have been reported in patients with chronic kidney disease (CKD) and infectious disease. We describe three cases of PRES in patients with CKD triggered by various infectious diseases. Characteristic hyperintense signals on magnetic resonance imaging (MRI) indicating reversible vasogenic brain oedema in various parts of the brain were observed. To explain the pathophysiology of PRES, the hypertension/hyperperfusion and hypoperfusion/vasoconstriction theories have been proposed. Patients with CKD have many complications including uraemia, hypertension, and immunosuppression. Therefore, physicians should recognize that patients with CKD are at high risk of PRES triggered by infectious diseases and promptly diagnose PRES because immediate treatment of the triggers often leads to complete resolution.

Selective plasma exchange can reduce auto-antibodies in patients with bullous pemphigoid without affecting factor XIII and fibrinogen.

Bullous pemphigoid (BP) is an autoimmune blistering skin disorder characterized by circulating serum IgG antibodies against two hemidesmosomal proteins: BP180 and BP230. Fundamentally, immunosuppressive therapies are administered to treat this disease, but plasmapheresis can be added for refractory patients. We experienced the case of a 63-year-old patient with refractory BP for which we administered double filtration plasmapheresis (DFPP). His skin lesions improved along with decreased IgG BP180 antibodies, but factor XIII (FXIII) and fibrinogen were also reduced by DFPP repetition. Reportedly, deficiency of those factors can cause lethal bleeding. Especially, decreased FXIII cannot be detected by prolongation of bleeding or coagulation time. To prevent further reduction of those factors and bleeding complications, DFPP was switched to selective plasma exchange (SePE), a new modality of plasmapheresis that uses a membrane plasma separator with smaller than ordinary pores. SePE further reduced pathogenic IgG BP180 antibodies, but FXIII and fibrinogen recovered. For this case, we measured the mean of reduction ratios in serum IgG and FXIII both before and after plasmapheresis sessions and detected the decreased levels of FXIII and fibrinogen during DFPP. We were able to switch to SePE from DFPP appropriately before any bleeding event occurred. The utility of SePE was demonstrated, especially for the reduction of pathogenic antibodies with retention of FXIII and fibrinogen, which have the longest half-lives among coagulation factors and which take a long time to recover.