DDAH1 promotes neurogenesis and neural repair in cerebral ischemia

Choline acetyltransferase(ChAT)-positive neurons in neural stem cell(NSC)niches can evoke adult neurogenesis(AN)and restore impaired brain function after injury,such as acute ischemic stroke(AIS).However,the relevant mechanism by which ChAT+neurons develop in NSC niches is poorly understood.Our RNA-seq analysis revealed that dimethylarginine dimethylaminohydrolase 1(DDAH1),a hydrolase for asymmetric NG,NG-dimethylarginine(ADMA),regulated genes responsible for the synthesis and transportation of acetylcholine(ACh)(Chat,Slc5a7 and Slc18a3)after stroke insult.The dual-luciferase reporter assay further suggested that DDAH1 controlled the activity of ChAT,possibly through hypoxia-inducible factor 1α(HIF-1α).KC7F2,an inhibitor of HIF-1α,abolished DDAH1-induced ChAT expression and suppressed neurogenesis.As expected,DDAH1 was clinically elevated in the blood of AIS patients and was positively correlated with AIS severity.By comparing the results among Ddah1 general knockout(KO)mice,transgenic(TG)mice and wild-type(WT)mice,we discovered that DDAH1 upregulated the proliferation and neural differentiation of NSCs in the subgranular zone(SGZ)under ischemic insult.As a result,DDAH1 may promote cognitive and motor function recovery against stroke impairment,while these neuroprotective effects are dramatically suppressed by NSC conditional knockout of Ddah1 in mice.

Hepatic DDAH1 mitigates hepatic steatosis and insulin resistance in obese mice: Involvement of reduced S100A11 expression

Dimethylarginine dimethylaminohydrolase 1(DDAH1)is an important regulator of plasma asymmetric dimethylarginine(ADMA)levels,which are associated with insulin resistance in patients with nonalcoholic fatty liver disease(NAFLD).To elucidate the role of hepatic DDAH1 in the pathogenesis of NAFLD,we used hepatocyte-specific Ddah1-knockout mice(Ddah1HKO)to examine the progress of high-fat diet(HFD)-induced NAFLD.Compared to diet-matched flox/flox littermates(Ddah1f/f),Ddah1HKO mice exhibited higher serum ADMA levels.After HFD feeding for 16 weeks,Ddah1HKO mice developed more severe liver steatosis and worse insulin resistance than Ddah1f/f mice.On the contrary,overexpression of DDAH1 attenuated the NAFLD-like phenotype in HFD-fed mice and ob/ob mice.RNA-seq analysis showed that DDAH1 affects NF-kB signaling,lipid metabolic processes,and immune system processes in fatty livers.Furthermore,DDAH1 reduces S100 calcium-binding protein A11(S100A11)possibly via NF-kB,JNK and oxidative stress-dependent manner in fatty livers.Knockdown of hepatic S100a11 by an AAV8-shS100a11 vector alleviated hepatic steatosis and insulin resistance in HFD-fed Ddah1HKO mice.In summary,our results suggested that the liver DDAH1/S100A11 axis has a marked effect on liver lipid metabolism in obese mice.Strategies to increase liver DDAH1 activity or decrease S100A11 expression could be a valuable approach for NAFLD therapy.