BACKGROUND: Obesity is the main risk factor leading to the development of various respiratory diseases, such as asthma and pulmonary hypertension. Pulmonary microvascular endothelial cells (PMVECs) play a significant role in the development of lung diseases. Aconitate decarboxylase 1 (Acod1) mediates the production of itaconate, and Acod1/itaconate axis has been reported to play a protective role in multiple diseases. However, the roles of Acod1/itaconate axis in the PMVECs of obese mice are still unclear.
METHODS: mRNA-seq was performed to identify the differentially expressed genes (DEGs) between high-fat diet (HFD)-induced PMVECs and chow-fed PMVECs in mice (|log2 fold change| ≥ 1, p ≤ 0.05). Free fatty acid (FFA) was used to induce cell injury, inflammation and mitochondrial oxidative stress in mouse PMVECs after transfection with the Acod1 overexpressed plasmid or 4-Octyl Itaconate (4-OI) administration. In addition, we investigated whether the nuclear factor erythroid 2-like 2 (Nrf2) pathway was involved in the effects of Acod1/itaconate in FFA-induced PMVECs.
RESULTS: Down-regulated Acod1 was identified in HFD mouse PMVECs by mRNA-seq. Acod1 expression was also reduced in FFA-treated PMVECs. Acod1 overexpression inhibited cell injury, inflammation and mitochondrial oxidative stress induced by FFA in mouse PMVECs. 4-OI administration showed the consistent results in FFA-treated mouse PMVECs. Moreover, silencing Nrf2 reversed the effects of Acod1 overexpression and 4-OI administration in FFA-treated PMVECs, indicating that Nrf2 activation was required for the protective effects of Acod1/itaconate.
CONCLUSIONS: Our results demonstrated that Acod1/Itaconate axis might protect mouse PMVECs from FFA-induced injury, inflammation and mitochondrial oxidative stress via activating Nrf2 pathway. It was meaningful for the treatment of obesity-caused pulmonary microvascular endotheliopathy.

BACKGROUND: Previous studies have revealed that Sirt3 deficiency is associated with several inflammatory responses. The purpose of this study is to investigate the role and potential molecular mechanisms of Sirt3 in the inflammation induced by monosodium urate (MSU) crystals.
METHODS: The Sirt3 expression level in the peripheral blood mononuclear cells (PBMCs) of patients with gout was measured. Function and molecular mechanism of Sirt3 in MSU crystal-induced inflammation were investigated in bone marrow-derived macrophages (BMDMs), C57BL/6 mouse, and Sirt3-/- mouse.
RESULTS: Sirt3 expression was decreased in the PBMCs of patients with gout. Sirt3 agonist (Viniferin) inhibited the acetylation levels of mitochondrial proteins including the SOD2 protein. RNA sequencing, bio-informatics analysis, RT-PCR, and Western blot demonstrated that Sirt3 could suppress the expression of Acod1 (Irg1), which plays an important role in gout. In BMDMs treated with palmitic acid (C16:0) plus MSU crystals, Acod1 knockdown repressed mitochondrial reactive oxygen species (mtROS) over-production, macrophage migration, and mitochondrial fragmentation, and Acod1 improved AMPK activity. The over-expression of Acod1 did not significantly affect the level of itaconic acid, but greatly decreased the levels of some important intermediate metabolites of the tricarboxylic acid (TCA) cycle. These data indicate that Acod1 exerts a pro-inflammatory role in MSU crystal-induced inflammation and is independent of the metabolic level of itaconic acid. Sirt3 deficiency exacerbates inflammatory response induced by MSU crystals in vitro and in vivo.
CONCLUSIONS: The current study has shown that Sirt3 can alleviate the MSU crystal-induced inflammation by inhibiting the expression of Acod1.

Cepharanthine (CEP), a bisbenzylisoquinoline alkaloid from tubers of Stephania, protects against some inflammatory diseases. Aconitate decarboxylase 1 (ACOD1) is also known as immune-responsive gene 1 (IRG1), which plays an important immunometabolism role in inflammatory diseases by mediating the production of itaconic acid. ACOD1 exhibits abnormal expression in ulcerative colitis (UC). However, whether CEP can combat UC by affecting ACOD1 expression remains unanswered. This study was designed to explore the protective effects and mechanisms of CEP in treating colitis through in vitro and in vivo experiments. In vitro assays indicated that CEP inhibited LPS-induced secretion of pro-inflammatory cytokines and ACOD1 expression in RAW264.7 macrophages. Additionally, in the mouse model of DSS-induced colitis, CEP decreased macrophage infiltration and ACOD1 expression in colon tissue. After treatment with antibiotics (Abx), the expression of ACOD1 changed with the composition of gut microbiota. Correlation analysis also revealed that Family-XIII-AD3011-group and Rumini-clostridium-6 were positively correlated with ACOD1 expression level. Additionally, data of the integrative Human Microbiome Project (iHMP) showed that ACOD1 was highly expressed in the colon tissue of UC patients and this expression was positively correlated with the severity of intestinal inflammation. Collectively, CEP can counter UC by modulating gut microbiota and inhibiting the expression of ACOD1. CEP may serve as a potential pharmaceutical candidate in the treatment of UC.