ABSTRACT
BACKGROUND Formation of schistosomal granulomata surrounding the ova can result in schistosomiasis-associated liver fibrosis (SSLF). The current standard of treatment is praziquantel (PZQ), which cannot effectively reverse SSLF. The role of the cannabinoid (CB) receptor family in liver fibrosis has recently been highlighted. OBJECTIVES This study aimed to assess the therapeutic effect of CB1 receptor antagonism in reversing SSLF in a murine model of Schistosoma mansoni infection. METHODS One hundred male Swiss albino mice were divided equally into five groups: healthy uninfected control (group I), infected control (group II), PZQ treated (group III), rimonabant (RIM) (SR141716, a CB1 receptor antagonist)-treated (group IV) and group V was treated with combined PZQ and RIM. Liver sections were obtained for histopathological examination, alpha-1 smooth muscle actin (α-SMA) immunostaining and assessment of CB1 receptor expression using real-time polymerase chain reaction (RT-PCR). FINDINGS The most effective reduction in fibrotic marker levels and granuloma load was achieved by combined treatment with PZQ+RIM (group V): CB1 receptor expression (H = 26.612, p < 0.001), number of α-SMA-positive cells (F = 57.086, p < 0.001), % hepatic portal fibrosis (F = 42.849, p < 0.001) and number of granulomata (F = 69.088, p < 0.001). MAIN CONCLUSIONS Combining PZQ with CB1 receptor antagonists yielded the best results in reversing SSLF. To our knowledge, this is the first study to test this regimen in S. mansoni infection.
Subject(s)
Humans , Fibrosis/diagnosis , Typhus, Endemic Flea-Borne/transmission , Liver/physiopathology , Receptors, CannabinoidABSTRACT
Objective: LMJ07 is a novel cannabinoid receptorl (CB1R) selective antagonist discovered by our lab. In the present study, its affinity and antagonistic activity against CB1R were evaluated at the molecular and cellular levels by receptor binding experiment, CB1R internalization experiment and by monitoring the change in cytoskeletal and intracellular signal induced by CB1R activation. Methods: With the CB1R selective antagonist rimonabant (SR141716A) as control, the affinity and selectivity of LMJ07 to CB1R and CB2R were assayed by radioligand binding assays, and the G protein-independent antagonistic activity against cannabinoid receptor (CBR) was assayed by enhanced green fluorescein protein (EGFP)-CBR internalization with hierarchiae cluscer anclysis (HCA) analysis. At the same time, we evaluated the changes in cytoskeletal and the intracellular cAMP levels in response to LMJ07 treatment in CHO-CB1 cells by Cellkey label-free assays and homogeneous time-resolved fluorescence (HTRF). Additionally, we also confirmed the CB1R antagonistic efficacy of LMJ07 by detecting the content of Ca2+ in primary cultured hippocampal neuronal cells which could express CB1R with continuous fluorescence detection technology. Results: LMJ07 is a selective CB1R antagonist with high affinity, which can selectively antagonize receptor endocytosis induced by CB1RactivationIt’s affinity and antagonistic efficacy to CB1R were equal to those of rimonabant. In CHO-CB1 cells, LMJ07 (0.01-10μmol/L)could dose-dependently inverse the change in cytoskeletal as well as the increase in intracellular cAMP induced by CBR agonist Win55212-2. In the primary cultured hippocampal neuronal cells, LMJ07 (10 nmol/L-1 μmol/L) could block the increase in [Ca2+] induced by CB1R agonist Win55212-2. Conclusion: LMJ07 is a new selective CB1R antagonist, which shows equal affinity and antagonistic activity against CB1R as the widely accepted CB1R antagonist rimonabant. In addition, the combination of high content analysis (HCS) and Cellkey label-free assay provides a better research tool for rapid and high throughput screening of novel CB1R antagonists.