TMAO Aggregates Neurological Damage Following Ischemic Stroke by Promoting Reactive Astrocytosis and Glial Scar Formation via the Smurf2/ALK5 Axis

Abstract

Ischemic stroke has been reported to cause significant changes to memory, thinking, and behavior. Intriguingly, recently reported studies have indicated the association of Trimethylamine N-oxide (TMAO) with the acute phase of ischemic stroke. However, the comprehensive underlying mechanism remained unknown. The objective of the present study was to investigate the association between TMAO and recovery of neurological function after ischemic stroke. For this purpose, a middle cerebral artery occlusion/reperfusion (MCAO/R) rat model was established and treated with TMAO or/and sh-ALK5, followed by the neurological function evaluation. Behaviors of rats were observed through staircase and cylinder tests. Moreover, the expression of Smurf2 and ALK5 was detected by immunohistochemistry while expression of GFAP, Neurocan, and Phosphacan in brain tissues was determined by immunofluorescence. Thereafter, gain- and loss-of-function assays in astrocytes, the proliferation, viability, and migration were evaluated by the EdU, CCK-8, and Transwell assays. Besides, Smurf2 mRNA expression was determined by the RT-qPCR, whereas, Smurf2, ALK5, GFAP, Neurocan, and Phosphacan expression was evaluated by the Western blotting. Finally, the interaction of Smurf2 with ALK5 and ALK5 ubiquitination was assessed by the co-immunoprecipitation. Notably, our results showed that TMAO promoted the proliferation of reactive astrocyte and formation of glial scar in MCAO/R rats. However, this effect was abolished by the Smurf2 overexpression or ALK5 silencing. We further found that TMAO upregulated the ALK5 expression by inhibiting the ubiquitination role of Smurf2. Overexpression of ALK5 reversed the inhibitory effect of Smurf2 on astrocyte proliferation, migration, and viability. Collectively, our work identifies the evolutionarily TMAO/Smurf2/ALK5 signaling as a major genetic factor in the control of reactive astrocyte proliferation and glial scar formation in ischemic stroke, thus laying a theoretical foundation for the identification of ischemic stroke.

Regulation of blood–brain barrier integrity by microbiome-associated methylamines and cognition by trimethylamine N-oxide

“…The primary focus of this work was on the effects of TMAO upon the BBB, but this is not necessarily the only CNS target for the methylamine. Our data add to the evidence suggesting that astrocytes [ 66 , 67 ] and microglia [ 68 , 69 ] may respond to TMAO treatment, although it is notable that previous studies have shown pro-activating effects of TMAO at supra-physiological concentrations (> 50 μM). An intriguing finding of the current study is the brain region selectivity in the effects of long-term LPS and/or TMAO treatment upon parenchymal glia, with astrocytes and microglia of the entorhinal cortex showing clear LPS-induced, TMAO-sensitive activation, whereas the same cell types in the neighbouring hippocampus appeared resistant to either stimulus.…”

Regulation of blood–brain barrier integrity by microbiome-associated methylamines and cognition by trimethylamineN-oxide

“…The primary focus of this work was on the effects of TMAO upon the BBB, but this is not necessarily the only CNS target for the methylamine. Our data add to the evidence suggesting that astrocytes [66,67] and microglia [68,69] may respond to TMAO treatment, although it is notable that previous studies have shown pro-activating effects of TMAO at supraphysiological concentrations (>50 µM). An intriguing finding of the current study is the brain region selectivity in the effects of long-term LPS and/or TMAO treatment upon parenchymal glia, with astrocytes and microglia of the entorhinal cortex showing clear LPS-induced, TMAO-sensitive activation, whereas the same cell types in the neighbouring hippocampus appeared resistant to either stimulus.…”

Different gender-derived gut microbiota influence stroke outcomes by mitigating inflammation

“…TMAO, SCFAs and Trp are three bacterial metabolites that have been shown to be associated with stroke [48][49][50]. TMAO is the product of some dietary nutrients, such as L-carnitine, phosphatidylcholine and choline, processed by intestinal microorganisms and transformed by heparin monooxygenase [51].…”