Diosmetin Suppresses Neuronal Apoptosis and Inflammation by Modulating the Phosphoinositide 3-Kinase (PI3K)/AKT/Nuclear Factor-κB (NF-κB) Signaling Pathway in a Rat Model of Pneumococcal Meningitis

Bacterial meningitis has a high mortality rate and can be challenging to diagnose and manage. This study aimed to evaluate the effect of diosmetin in a rat model of Streptococcus pneumoniae meningitis and to investigate the mechanism of action. Forty rats included a treatment group (n=30) that underwent intracisternal injection with S. pneumoniae, and a sham group (n=10) that underwent intracisternal injection with normal saline. In the treatment group, four days before the inoculation of the bacteria, rats were pre-treated with oral diosmetin 100 mg/kg (n=10) and 200 mg/kg (n=10), and the negative control was pre-treated with normal saline (n=10). Bacterial meningitis was confirmed one day after inoculation by cerebrospinal fluid (CSF) bacterial titer and neurological score. In rat brain tissue, levels of inflammatory mediators were determined by enzyme-linked immunosorbent assay (ELISA) and western blot for protein kinase B (Akt), phosphoinositide 3-kinase (PI3K), myeloid differentiation primary response 88 (MyD88), and nuclear factor-kappaB (NF-kappaB), and the TUNEL assay for apoptosis was performed. In the diosmetin-treated group compared with negative control group, the CSF bacterial titer and the level of pro-inflammatory mediators, and the neurological score, were significantly reduced (p<0.01). In the rat hippocampal tissue, levels of Akt, PI3K, MyD88 and NF-kappaB, and the number of TUNEL-positive apoptotic cells were significantly reduced in the diosmetin-treated group compared with negative control group (p<0.01). In a rat model of bacterial meningitis due to S. pneumoniae, diosmetin reduced neuroinflammation, and neuronal apoptosis by modulating the PI3K/AKT/NF-kappaB signaling pathway.