Persistence of Gut Microbiota Dysbiosis and Chronic Systemic Inflammation After Cerebral Infarction in Cynomolgus Monkeys

Abstract

Background: The bidirectional interaction between the gut and brain after stroke through the immune-mediated pathway has been studied. However, the long-term effects of gut microbiota and systemic immune homeostasis after cerebral ischemia remain unclear. We examined long-term changes in the gut microbiota and systemic inflammatory cytokines after cerebral infarction in cynomolgus monkeys. Methods: Twelve monkeys underwent successful distal M1 segment of the left middle cerebral artery occlusion (MCAO) and were randomly and equally assigned to the MCAO-1.5 m, MCAO-6 m, and MCAO-12 m groups, which were sacrificed 1.5, 6, and 12 months after cerebral infarction induction, respectively. Four monkeys that underwent a sham operation were sacrificed 12 months later. The gut microbiota and short-chain fatty acids (SCFAs) were analyzed by 16S rDNA sequencing and gas chromatography mass spectrometry, respectively. Histological examinations of the transverse colon were performed. Plasma D-lactate, zonulin, lipopolysaccharide (LPS), tumor necrosis factor (TNF-α), interferon (IFN)-γ, and interleukin (IL)-6 were detected by immunoassay kits. Results: The levels of the Bacteroidetes phylum and Prevotella genus were significantly increased, while the Firmicutes phylum as well as the Faecalibacterium, Oscillospira , and Lactobacillus genera were decreased after cerebral infarction. Gut-originating SCFAs were significantly decreased 6 and 12 months after cerebral infarction ( P < 0.05). We observed intestinal mucosal damage, evaluated by Chiu's score. Plasma D-lactate, zonulin, LPS, TNF-α, IFN-γ, and IL-6 were significantly increased after cerebral infarction ( P < 0.05). Additionally, the increases in plasma LPS, TNF-α, IFN-γ, and IL-6 after cerebral infarction coincided with overgrowth of the Bacteroidetes phylum ( P < 0.001). Conclusion: Cerebral infarction induces persistent host gut microbiota dysbiosis, intestinal mucosal damage, and chronic systemic inflammation in cynomolgus monkeys.

Gut Microbiota in Acute Ischemic Stroke: From Pathophysiology to Therapeutic Implications

“…The consequences of this remain unclear, as detrimental effects to regulatory T cells after AIS have been reported (51). Release into the systemic circulation of cytokines and chemokines produced in the brain after AIS may exert a potential influence on microbiota composition and dysbiosis (52). T lymphocytes, especially regulatory and γδT-cells, play a pivotal role in how the microbiota can modify infarct size and neurological function after AIS (7,53).…”

“…An interesting experimental study showed that AIS in cynomolgus monkeys induced a long-term, persistent increase in levels of LPS and pro-inflammatory cytokines in plasma, which correlated with the relative abundance of the phylum Bacteroidetes in the gut microbiota. Additionally, intestinal dysbiosis and mucosal damage persisted for up to 12 months after AIS ( 52 ). Clinical evidences ( 56 , 57 ) concluded that after AIS the commensal flora changes in favor of opportunistic pathogens, such as Enterobacter, Megasphaera, Oscillibacter, Desulfovibrio, Odoribacter , and Akkermansia ( 58 ), instead of commensals such as Bacteroides, Prevotella , and Faecalibacterium .…”

Experimental Stroke Induces Chronic Gut Dysbiosis and Neuroinflammation in Male Mice

“…We observed that prolonged intestinal inflammatory pathology accompanies the changes that we see in bacterial abundance. More recently, mucosal and villi damage has been observed in the colons of cynomolgus monkeys at 1.5, 6, and 12 months after permanent MCAO [81]. Although specific mechanisms linking gut dysbiosis and stroke remain elusive, the most likely mechanisms include: increased permeability of the intestinal barrier and bacterial motility, suppression of systemic immunity, release of proinflammatory factors from the brain infarct, and activation of the sympathetic nervous system [82,83].…”

The Role of Gut Microbiota in an Ischemic Stroke

“…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 ]. Increased Bacteroidetes abundance was also found three days after the occurrence of an ischemic stroke in mice, which is considered a characteristic feature of post-stroke dysbiosis [ 28 ].…”

“…In contrast, a clinical study in which stool samples were taken for two days after admission showed a decrease in Bacteroidetes levels in patients with an acute ischemic stroke and a transient ischemic attack [ 36 ]. In the study of monkeys after a focal brain ischemia, an increased relative abundance of Prevotella was found, suggesting that this type may be associated with an inflammatory response following a stroke [ 35 ]. In monkeys after a local cerebral ischemia, reduced relative levels of Faecalibacterium , Streptococcus , Lactobacillus and Oscillospira were observed [ 35 ].…”