The NLRP3 Inflammasome Is a Major Cause of Acute Renal Failure Induced by Polypeptide Antibiotics.

Drug-induced acute renal failure (ARF) is a public health concern that hinders optimal drug therapy. However, pathological mechanisms of drug-induced ARF remain to be elucidated. Here, we show that a pathological process of drug-induced ARF is mediated by proinflammatory cross-talk between kidney tubular cells and macrophages. Both polymyxin B and colistin, polypeptide antibiotics, frequently cause ARF, stimulated the ERK and NF-κB pathways in kidney tubular cells, and thereby upregulated M-CSF and MCP-1, leading to infiltration of macrophages into the kidneys. Thereafter, the kidney-infiltrated macrophages were exposed to polypeptide antibiotics, which initiated activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome. Interestingly, blockade of the NLRP3 activation clearly ameliorated the pathology of ARF induced by polypeptide antibiotics, suggesting that a combination of the distinct cellular responses to polypeptide antibiotics in kidney tubular cells and macrophages plays a key role in the pathogenesis of colistin-induced ARF. Thus, our results provide a concrete example of how drugs initiate ARF, which may give insight into the underlying pathological process of drug-induced ARF.

LLPS of SQSTM1/p62 and NBR1 as outcomes of lysosomal stress response limits cancer cell metastasis.

Liquid droplet has emerged as a flexible intracellular compartment that modulates various cellular processes. Here, we uncover an antimetastatic mechanism governed by the liquid droplets formed through liquid-liquid phase separation (LLPS) of SQSTM1/p62 and neighbor of BRCA1 gene 1 (NBR1). Some of the tyrosine kinase inhibitors (TKIs) initiated lysosomal stress response that promotes the LLPS of p62 and NBR1, resulting in the spreading of p62/NBR1 liquid droplets. Interestingly, in the p62/NBR1 liquid droplet, degradation of RAS-related C3 botulinum toxin substrate 1 was accelerated by cellular inhibitor of apoptosis protein 1, which limits cancer cell motility. Moreover, the antimetastatic activity of the TKIs was completely overridden in p62/NBR1 double knockout cells both in vitro and in vivo. Thus, our results demonstrate a function of the p62/NBR1 liquid droplet as a critical determinant of cancer cell behavior, which may provide insight into both the clinical and biological significance of LLPS.

Low Ascorbic Acid Intake Induces Inflammatory Changes in Intestine and Liver of ODS Rats.

We previously demonstrated that ascorbic acid (AsA) deficiency, caused by an AsA-free diet, induces inflammatory changes in the liver and intestine of osteogenic disorder Shionogi (ODS) rats that cannot synthesize AsA. However, whether low AsA intake induces inflammatory changes remains unknown. Here, we assessed the inflammatory changes in ODS rats caused by low AsA intake and compared them to ODS rats that were fed a diet supplemented with sufficient amounts of AsA (300 mg/kg). Male ODS rats (12-wk-old) were fed an AsA-free diet (0 ppm group), AsA 20 mg/kg diet (20 ppm group), AsA 40 mg/kg diet (40 ppm group) or AsA 300 mg/kg diet (300 ppm group) for 22 d. The hepatic mRNA levels of acute phase proteins, including C-reactive protein (CRP) and haptoglobin, were higher in the 0 and 20 ppm groups, than in the 300 and 40 ppm groups, but were not significantly higher in the 20 ppm group. Serum CRP concentrations were significantly higher in the 0 and 20 ppm groups than in the 300 and 40 ppm groups. Jejunal and ileal interleukin-1ß (IL-1ß) mRNA levels were higher in the 0 and 20 ppm groups than in the 300 ppm group. Jejunal and ileal IL-6 mRNA levels tended to be higher in the 0 and 20 ppm groups than in the 300 ppm group. Furthermore, the portal IL-6 concentration gradually increased with decrease in the AsA intake. Thus, inflammatory changes could occur in both AsA-deficient ODS rats and ODS rats with low AsA intake.

Ascorbic acid deficiency induces hepatic and intestinal expression of inflammation-related genes irrespective of the presence or absence of gut microbiota in ODS rats.

We have previously demonstrated that ascorbic acid (AsA) deficiency causes inflammatory changes in the liver and intestine in Osteogenic Disorder Shionogi (ODS) rats, which are unable to synthesize AsA. We have suggested that AsA deficiency increased intestinal interleukine (IL)-6 production, stimulating hepatic acute phase proteins (APPs) expression via the portal vein. In this study, we determined whether these hepatic and intestinal inflammatory changes by AsA deficiency are induced in germ-free (GF) ODS rats. For 18 days, male specific pathogen-free (SPF) ODS rats were fed the basal diet containing 600 mg AsA/kg (control group) or the AsA-free diet (AsA-deficient group) in SPF conditions, while male GF ODS rats were fed the basal diet (control group) or the AsA-free diet (AsA-deficient group) in GF conditions. Firstly, AsA deficiency significantly elevated the hepatic expression of APPs in both SPF and GF rats. In hepatic mRNA levels of some APPs, significant interaction between GF and AsA-deficiency effects was observed. Secondly, AsA deficiency elevated intestinal IL-6 and IL-1ß mRNA levels in both SPF and GF rats, and significant interaction between GF and AsA-deficiency effects was observed in these mRNA levels of jejunum and cecum. In SPF and GF rats, AsA deficiency elevated portal IL-6 concentration. These results show that AsA deficiency caused hepatic and intestinal inflammatory changes in both the GF and SPF ODS rats and indicate that AsA deficiency could directly induce intestinal inflammatory changes without the involvement of gut microbiota.

Ascorbic acid deficiency increases hepatic expression of acute phase proteins through the intestine-derived IL-6 and hepatic STAT3 pathway in ODS rats.

We have previously shown that ascorbic acid (AsA) deficiency elevates hepatic expression of acute phase proteins (APPs), inflammatory markers, in Osteogenic Disorder Shionogi (ODS) rats, which are unable to synthesize AsA. However, the precise mechanisms of this elevation are unknown. Signal transducer and activator of transcription 3 (STAT3) is one of the transcription factors inducing the expression of APPs and is activated by several cytokines including interleukin-6 (IL-6). The aim of this study was to determine whether AsA deficiency stimulates hepatic STAT3 activation and increases intestinal production of proinflammatory cytokines such as IL-6. Male ODS rats (6 weeks old) were fed either a basal diet containing 300 mg AsA/kg (control group) or an AsA-free diet (AsA-deficient group) for 18 days. AsA deficiency gradually and simultaneously elevated both mRNA levels of APPs (haptoglobin, α1-acid glycoprotein, C-reactive protein and α2-macroglobulin) and nuclear level of phosphorylated STAT3 (activated STAT3) in the liver. These results showed that the AsA-deficiency-induced expression of hepatic APPs is stimulated by proinflammatory cytokines activating STAT3. On day 14, AsA deficiency significantly elevated IL-6 mRNA level in the ileum and the concentration of IL-6 in portal blood. Furthermore, the portal concentration of IL-6 positively correlated with hepatic mRNA levels of STAT3-regulated genes. These findings suggest that IL-6, produced in the intestine as a result of AsA deficiency, is recruited to the liver via the portal vein and contributes to hepatic STAT3 activation and the elevated expression of APPs.