Di-san junyi daxue xuebao (May 2022)
Cannabinoid receptor 2 agonist AM1241 inhibits fibrous scarring after spinal cord injury in rats
Abstract
Objective To determine the role of cannabinoid receptor 2 (CBR2) agonist, AM1241, in the formation of fibrous scars in rats after spinal cord injury and elucidate the underlying mechanism. Methods A total of 144 female Sprague-Dawley rats were selected and divided into 4 groups: sham operation group (n=24, only the lamina was removed to expose the dura mater, and 3 mL/kg normal saline was given postoperatively), vehicle group (n=40, the rats was inflicted to establish a model of dorsal hemisection and then given 3 mL/kg of normal saline), AM1241 group (n=40, the rats were given 3 mg/kg AM1241 on the basis of the vehicle group), and AM1241+AM630 group (n=40, after modeling, the rats were given 3 mg/kg AM630, CBR2 antagonist, in 30 min before AM1241 treatment). The corresponding drugs were injected intraperitoneally to each group, once a day, for 14 consecutive days. Immunofluorescence staining, Western blotting and ELISA were performed to evaluate the inhibitory effects of AM1241 on fibrous scar formation, and behavioral electrophysiology were carried out to detect its effect on neurological function. Results After spinal cord injury, AM1241 significantly reduced the expression of the main molecules in fibrous scars, as well as the area of fibrous scar, while the treatment of AM630 reversed above phenomena, with statistical significances (P < 0.05). The results of tubulin βⅢ immunofluorescence staining, behavioral assessment as well as electrophysiological experiments demonstrated that AM1241 could promote the survival of spinal cord neurons, improve neurological function after injury, such as Basso-Beattie-Bresnahan(BBB) score and angle of oblique board test [vehicle group vs AM1241 group vs AM1241+AM630 group: 15.38±0.38 vs 18.38± 0.50 vs 15.50±0.33, P < 0.05; (54.25±1.25)° vs (64.25±1.05)° vs (54.75±0.49)°, P < 0.05]. ELISA indicated that AM1241 inhibited the expression of iNOS, TNF-α and IL-1β (markers of M1-type macrophages, P < 0.01), enhanced the expression of CD206 and Arg-1 (markers of M2-type macrophages, P < 0.05), and decreased the expression of TGF-β1 (fibrogenic factor, P < 0.01). The treatment of CBR2 antagonist, AM630 led to opposite results. Conclusion Stimulation of CBR2 decreases fibrous scarring and improves neurological function after spinal cord injury in rats, which might be attained by influencing macrophage polarization.
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