Arginase 2 attenuates ulcerative colitis by antioxidant effects of spermidine.

BACKGROUND: Spermidine suppress oxidative stress and is involved in various disease pathogenesis including ulcerative colitis (UC). Arginase 2 (ARG2) plays a central role in the synthesis of spermidine. This study aimed to clarify the effect of endogenously produced spermidine on colitis. METHODS: The physiological role of ARG2 and spermidine was investigated using Arg2-deficient mice with reduced spermidine. Immunohistochemical staining of the rectum was used to analyze ARG2 expression and spermidine levels in healthy controls and UC patients. RESULTS: In mice with dextran sulfate sodium-induced colitis, ARG2 and spermidine levels were increased in the rectal epithelium. Spermidine protects colonic epithelial cells from oxidative stress and Arg2 knockdown cells reduced antioxidant activity. Organoids cultured from the small intestine and colon of Arg2-deficient mice both were more susceptible to oxidative stress. Colitis was exacerbated in Arg2-deficient mice compared to wild-type mice. Supplementation with spermidine result in comparable severity of colitis in both wild-type and Arg2-deficient mice. In the active phase of UC, rectal ARG2 expression and spermidine accumulation were increased compared to remission. ARG2 and spermidine levels were similar in healthy controls and UC remission patients. CONCLUSIONS: ARG2 produces spermidine endogenously in the intestinal epithelium and has a palliative effect on ulcerative colitis. ARG2 and spermidine are potential novel therapeutic targets for UC.

Ustekinumab Decreases Circulating Th17 Cells in Ulcerative Colitis.

Objective T helper (Th) cells play a central role in the pathogenesis of ulcerative colitis (UC). The present study analyzed the changes in circulating T cells by administration of ustekinumab (UST), an interleukin-12/23p40 antibody. Methods CD4 T cells were isolated from peripheral blood at 0 and 8 weeks after UST treatment, and we analyzed the proportion of CD4 T cells by flow cytometry. Clinical information and laboratory data were obtained at 0, 8, and 16 weeks. Patients We evaluated 13 patients with UC who received UST for the induction of remission between July 2020 and August 2021. Results The median partial Mayo score improved from 4 (1-7) to 0 (0-6) (p<0.001) with UST. Among serological parameters, albumin concentrations, C-reactive protein concentrations, the sedimentation rate, and leucine-rich alpha 2 glycoprotein concentrations showed significant improvement with UST. A flow cytometric analysis of circulating CD4 T cells showed that the percentage of Th17 cells was significantly decreased by UST treatment in all patients (1.85% to 0.98%, p<0.0001). Th1 cells were significantly increased by UST treatment (9.52% to 10.4%, p<0.05), but Th2 and regulatory T cells were not significantly different. The high-Th17 subgroup had a significantly better partial Mayo score than the low-Th17 subgroup at 16 weeks after UST treatment (0 vs. 1, p=0.028). Conclusion Treatment with UST decreases circulating Th17 cells, suggesting that this change may be related to the anti-inflammatory effect of UC.

Arginase 2 Promotes Cisplatin-Induced Acute Kidney Injury by the Inflammatory Response of Macrophages.

Acute kidney injury (AKI) is a complex clinical syndrome with a rapid decrease in renal function caused by several different etiologies, including sepsis, ischemia, and the administration of nephrotoxic drugs. Tubular arginase 2 (ARG2), an arginine-metabolic enzyme, is a potential therapeutic target for AKI, but it has not been confirmed under various AKI conditions. The aim of this study was to investigate ARG2 as a therapeutic target for cisplatin-induced AKI. Cisplatin-treated mice with a genetic deficiency in Arg2 had significant amelioration of renal dysfunction, characterized by decreased acute tubular damage and apoptosis. In contrast, cisplatin-induced tubular toxicity was not ameliorated in proximal tubule cells derived from Arg2-deficient mice. Immunohistochemical analysis demonstrated the increased infiltration of ARG2-positive macrophages in kidneys damaged by cisplatin. Importantly, cisplatin-treated Arg2 knockout mice exhibited a significant reduction in kidney inflammation, characterized by the decreased infiltration of inflammatory macrophages and reduced gene expression of interleukin (IL)-6 and IL-1ß. The secretion of IL-6 and IL-1ß induced by lipopolysaccharides was decreased in bone marrow-derived macrophages isolated from Arg2-deficient mice. Furthermore, the lipopolysaccharide-induced elevation of mitochondrial membrane potential and production of reactive oxygen species were reduced in bone marrow-derived macrophages lacking Arg2. These findings indicate that ARG2 promotes the inflammatory responses of macrophages through mitochondrial reactive oxygen species, resulting in the exacerbation of AKI. Therefore, targeting ARG2 in macrophages may constitute a promising therapeutic approach for AKI.

Ferroptosis in the colon epithelial cells as a therapeutic target for ulcerative colitis.

BACKGROUND: Ferroptosis, a type of programmed cell death triggered by oxidative stress, was suspected to play a role in ulcerative colitis. Indigo naturalis is highly effective against ulcerative colitis, but its mechanism is unclear. This study found that indigo naturalis treatment suppressed ferroptosis. METHODS: We analyzed 770 mRNA expressions of patients with ulcerative colitis. Suppression of ferroptosis by indigo naturalis treatment was shown using a cell death assay. Malondialdehyde levels and reactive oxygen species were analyzed in CaCo-2 cells treated with indigo naturalis. Glutathione metabolism was shown by metabolomic analysis. Extraction of the ingredients indigo naturalis from the rectal mucosa was performed using liquid chromatograph-mass spectrometry. RESULTS: Gene expression profiling showed that indigo naturalis treatment increased antioxidant genes in the mucosa of patients with ulcerative colitis. In vitro analysis showed that nuclear factor erythroid-2-related factor 2-related antioxidant gene expression was upregulated by indigo naturalis. Indigo naturalis treatment rendered cells resistant to ferroptosis. Metabolomic analysis suggested that an increase in reduced glutathione by indigo naturalis. The protein expression of CYP1A1 and GPX4 was increased in the rectum by treatment with indigo naturalis. The main ingredients of indigo naturalis, indirubin and indigo inhibited ferroptosis. Indirubin was detected in the rectal mucosa of patients with ulcerative colitis who were treated with indigo naturalis. CONCLUSIONS: Suppression of ferroptosis by indigo naturalis in the intestinal epithelium could be therapeutic target for ulcerative colitis. The main active ingredient of indigo naturalis may be indirubin.

Spermidine from arginine metabolism activates Nrf2 and inhibits kidney fibrosis.

Kidney metabolism may be greatly altered in chronic kidney disease. Here we report that arginine metabolism is the most altered in unilateral ureteral obstruction (UUO)-induced fibrosis of the kidneys in metabolomic analysis. Spermidine is the most increased metabolite of arginine. In human glomerulonephritis, the amount of spermidine shown by immunostaining is associated with the amount of fibrosis. In human proximal tubule cells, spermidine induces nuclear factor erythroid 2-related factor 2 (Nrf2). Subsequently, fibrotic signals, such as transforming growth factor ß1 secretion, collagen 1 mRNA, and oxidative stress, represented by a decrease in the mitochondrial membrane potential is suppressed by spermidine. UUO kidneys of Arg2 knockout mice show less spermidine and significantly exacerbated fibrosis compared with wild-type mice. Nrf2 activation is reduced in Arg2 knockout UUO kidneys. Spermidine treatment prevents significant fibrotic progression in Arg2 knockout mice. Spermidine is increased in kidney fibrosis, but further increases in spermidine may reduce fibrosis.