Rosiglitazone regulates astrocyte polarization and neuroinflammation in a PPAR-γ dependent manner after experimental traumatic brain injury

Abstract

Background: Traumatic brain injury (TBI) is a leading cause of high mortality and disability worldwide. Overactivation of astrocytes and overexpression of inflammatory responses in the injured brain are characteristic pathological features of TBI. Rosiglitazone (ROS) is a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist known for its anti-inflammatory activity. However, the relationship between the inflammatory response involved in ROS treatment and astrocyte A1 polarization remains unclear.

Objective: This study aimed to investigate whether ROS treatment improves dysfunction and astrocyte A1 polarization induced after TBI and to elucidate the underlying mechanisms of these functions.

Methods: SD rats were randomly divided into sham operation group, TBI group, TBI+ROS group, and TBI+ PPAR-γ antagonist group (GW9662 + TBI). The rat TBI injury model was prepared by the CCI method; brain water content test and wire grip test scores suggested the prognosis; FJB staining showed the changes of ROS on the morphology and number of neurons in the peripheral area of cortical injury; ELISA, immunofluorescence staining, and western blotting analysis revealed the effects of ROS on inflammatory response and astrocyte activation with the degree of A1 polarization after TBI.

Results: Brain water content, inflammatory factor expression, and astrocyte activation in the TBI group were higher than those in the sham-operated group (P < 0.05); compared with the TBI group, the expression of the above indexes in the ROS group was significantly lower (P < 0.05). Compared with the TBI group, PPAR-γ content was significantly higher and C3 content was considerably lower in the ROS group (P < 0.05); compared with the TBI group, PPAR-γ content was significantly lower and C3 content was substantially higher in the inhibitor group (P < 0.05).

Conclusion: ROS can exert neuroprotective effects by inhibiting astrocyte A1 polarization through the PPAR-γ pathway based on the reduction of inflammatory factors and astrocyte activation in the brain after TBI.

Keywords: Astrocyte polarization; Neuroinflammation; PPAR-γ pathway; Rosiglitazone; Traumatic brain injury.