Distinct Commensal Bacterial Signature in the Gut Is Associated With Acute and Long-Term Protection From Ischemic Stroke

Abstract

Background and Purpose— Commensal gut bacteria have a profound impact on stroke pathophysiology. Here, we investigated whether modification of the microbiota influences acute and long-term outcome in mice subjected to stroke. Methods— C57BL/6 male mice received a cocktail of antibiotics or single antibiotic. After 4 weeks, fecal bacterial density of the 16S rRNA gene was quantitated by qPCR, and phylogenetic classification was obtained by 16S rRNA gene sequencing. Infarct volume and hemispheric volume loss were measured 3 days and 5 weeks after middle cerebral artery occlusion, respectively. Neurological deficits were tested by the Tape Test and the open field test. Results— Mice treated with a cocktail of antibiotics displayed a significant reduction of the infarct volume in the acute phase of stroke. The neuroprotective effect was abolished in mice recolonized with a wild-type microbiota. Single antibiotic treatment with either ampicillin or vancomycin, but not neomycin, was sufficient to reduce the infarct volume and improved motorsensory function 3 days after stroke. This neuroprotective effect was correlated with a specific microbial population rather than the total bacterial density. In particular, random forest analysis trained for the severity of the brain damage revealed that Bacteroidetes S24.7 and the enzymatic pathway for aromatic metabolism discriminate between large versus small infarct size. Additionally, the microbiota signature in the ampicillin-treated mice was associated with a reduced gut inflammation, long-term favorable outcome shown by an amelioration of the stereotypic behavior, and a reduction of brain tissue loss in comparison to control and was predictive of a regulation of short-chain fatty acids and tryptophan pathways. Conclusions— The findings highlight the importance of the intestinal microbiota in short- and long-term outcomes of ischemic stroke and raises the possibility that targeted modification of the microbiome associated with specific microbial enzymatic pathways may provide a preventive strategy in patients at high risk for stroke. Visual Overview— An online visual overview is available for this article.

Dynamic Changes in the Gut Microbiome at the Acute Stage of Ischemic Stroke in a Pig Model

“…It has been demonstrated that adjustments in the gut microbiome influence ischemic brain injury by altering immune homeostasis (Benakis et al, 2016;Singh et al, 2016) and neuroprotective cytokine production (Benakis et al, 2016). This suggests that the gut microbiome is another potential therapeutic target for stroke (Benakis et al, 2016;Singh et al, 2016Singh et al, , 2018Winek et al, 2016;Benakis et al, 2020). Studies of gut microbiome changes in stroke have demonstrated decreases in both commensal and beneficial genera, increases in pathogenic genera in human patients (Swidsinski et al, 2012;Yin et al, 2015), and substantial changes in the phylum Firmicutes, Bacteroidetes, and Actinobacteria in stroke mice (Singh et al, 2016).…”

The Role of Gut Microbiota in an Ischemic Stroke

“…However, the main obstacle to the clinical translation of microbiome study is the large variability between patients' intestinal microbiomes, which cannot be easily reproduced with animal models. Nevertheless, microbiome-based treatments can have a huge impact on improving post-stroke outcomes in the future [34,87,88].…”

“…Studies indicate the effect of intestinal microflora on a host stroke outcome, paying attention to two-way communication along the brain-gut axis [28,34]. Growth of Bacteroidetes after an ischemia was confirmed in monkeys [35].…”

“…In mice, the composition of the cecum microflora was found to change following a local cerebral ischemia, identifying specific changes in Peptococcaceae and Prevotellaceae that correlated with the extent of the injury [25]. It has also been shown that dysbiosis affects the outcome of an ischemic stroke by suppressing the effector T cell movement from the intestine to leptomeninges in a model of a local cerebral ischemia [34].…”

The Gut Ecosystem: A Critical Player in Stroke

“…Different studies observed an overall reduction of the Firmicutes, with a concomitant overgrowth of Bacteroidetes (Singh et al 2016 ; Spychala et al 2018 ). However, when analyzing microbiota changes at lower taxonomic ranks, there is a lack of consistency regarding the specific bacterial changes in clinical and experimental stroke (Benakis et al 2020a , b ). Differences in the location of fecal sampling (across the GI tract in mice, and stool samples in patients), the methods used for the extraction of genomic DNA and for 16S rRNA gene analysis, the severity of the stroke model and the baseline differences in the microbiota composition (the mouse origin or inter- and intra-individual variabilities in humans) could be confounding factors accounting for the contradictory results (Costello et al 2009 ; Sadler et al 2017 ; Stanley et al 2018 ).…”