Cannabinoid receptor-1 antagonism: a new perspective on treating a murine schistosomal liver fibrosis model

Issa, Yasmine Amr; El Achy, Samar Nabil; Mady, Rasha Fadly

doi:10.1590/0074-02760190062

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.

Key words:
cannabinoid receptor-1(CB1); schistosoma-associated liver fibrosis; rimonabant (SR141716); praziquantel; alpha smooth muscle actin

[TFN] Normally quantitative data was expressed as mean ± standard deviation and compared using analysis of (ANOVA) test, and post-hoc test (Tukey) for pairwise comparisons. While abnormally distributed data was expressed using median (min.-max.) and was compared using Kruskal Wallis test and post-hoc (Dunn’s multiple comparisons test) for pairwise comparisons. p1: p-value for comparing between praziquantel (PZQ) and rimonabant (RIM); p2: p-value for comparing between PZQ and PZQ+RIM; p3: p-value for comparing between RIM and PZQ+RIM; pcontrol: p-value for comparing between control group with each other group; RQ: relative quantification; Sig: significance; α-SMA: alpha smooth muscle actin. *: statistically significant at p ≤ 0.05.

RQ	Control (group II) (n = 20)	PZQ (group III) (n = 20)	RIM (group IV) (n = 20)	PZQ+RIM (group V) (n = 20)	Test of sig.	p-value
RQ	1 (1-1)	0.31 (0.07-0.9)	0.07 (0.01-0.5)	0.02 (0.06-0.1)	H = 30.966^*	< 0.0001^*
p_control		0.069	< 0.001^*	< 0.001^*
Statistical significance bet. groups		p₁ = 0.031^, p₂ = 0.001^, p₃ = 0.254
Fibrosis (%)	86.7 ± 4.1	57.3 ± 15.4	35 ± 12	21.8 ± 11.2	F = 42.849^*	< 0.001^*
p_control		< 0.001^*	< 0.001^*	< 0.001^*
Sig. bet. groups		p₁ = 0.001^, p₂ < 0.001^, p₃ = 0.081
Granulomata	17.5 ± 1	12.4 ± 1.5	14.9 ± 1.2	8.3 ± 1.6	F = 69.088^*	< 0.001^*
p_control		< 0.001^*	0.005^*	< 0.001^*
Sig. bet. groups		p₁ = 0.001^, p₂ < 0.001^, p₃ < 0.001^*
Average number of α-SMA-positive cells	74.7 ± 7.1	47.1 ± 15.1	29.2 ± 5.4	14.9 ± 5.5	F = 57.086^*	< 0.001^*
p_control		< 0.001^*	< 0.001^*	< 0.001^*
Sig. bet. groups		p₁ = 0.001^, p₂ < 0.001^, p₃ = 0.008^*