Pharmacokinetics-Based Chronoefficacy of Semen Strychni and Tripterygium Glycoside Tablet Against Rheumatoid Arthritis

Abstract

Rheumatoid arthritis is a systemic autoimmune disease characterized by synovial inflammation and bone destruction. Identifying drugs with time-varying efficacy and toxicity, and elucidating the mechanisms would help to improve treatment efficacy and reduce adverse effects. Here, we aimed to determine the chronoefficacy of semen strychni (SS) and tripterygium glycoside tablet (TGT) against rheumatoid arthritis in mice, and to investigate a potential role of circadian pharmacokinetics in generating chronoefficacy. SS extract and TGT suspension were prepared with ultrasonication. Effects of SS and TGT on collagen-induced arthritis (CIA) were evaluated by measuring TNF-α and IL-6 levels. SS dosed at ZT18 was more effective in protecting against CIA than drug dosed at ZT6 (i.e., lower levels of key inflammatory factors at ZT18 than at ZT6). This was accompanied by higher systemic exposure levels of strychnine and brucine (two main putative active ingredients of SS) in ZT18-treated than in ZT6-treated CIA mice. TGT dosing at ZT2 showed a better efficacy against CIA as compared to herb doing at ZT14. Consistently, ZT2 dosing generated a higher exposure of triptolide (a main putative active ingredient of TGT) as compared to ZT14 dosing in CIA mice. Moreover, strychnine, brucine, and triptolide significantly inhibited the proliferation of fibroblast-like synoviocytes, and reduced the production of TNF-α and IL-6 and the mRNAs of TNF-α, IL-6, COX-2, and iNOS, suggesting that they possessed an anti-arthritis activity. In conclusion, SS and TGT display chronoefficacy against rheumatoid arthritis in mice, that is attributed to circadian pharmacokinetics of main active ingredients. Our findings have implications for improving treatment outcomes of SS and TGT via timed delivery.

Keywords: chronoefficacy; dosing time; pharmacokinetics; rheumatoid arthritis; semen strychni; tripterygium glycoside tablet.

FIGURE 1

Therapeutic efficacy of SS in CIA mice (A) Schematic diagram for the experimental protocol (B) Plasma TNF-α and IL-6 levels in CIA mice after gavage with 20, 40, and 80 mg/kg SS extract or vehicle for 1 week. Data are mean ± SD (n = 5). *p < 0.05 (one-way ANOVA with Bonferroni post hoc test) (C) mRNA levels of TNF-α, IL-6, COX-2, and iNOS in CIA mice after gavage with 20, 40, and 80 mg/kg SS extract or vehicle for 1 week. Data are mean ± SD (n = 5). *p < 0.05 (one-way ANOVA with Bonferroni post hoc test) (D) Paw sizes in CIA mice before and after gavage of SS extract. Data are mean ± SD (n = 5). *p < 0.05 (one-way ANOVA with Bonferroni post hoc test) (E) H&E staining and histopathological scores. Data are mean ± SD (n = 5). *p < 0.05 (t test) (F) Plasma CK-BB and creatinine levels in normal mice treated with SS extract (40 mg/kg). Data are mean ± SD (n = 5).

FIGURE 2

Therapeutic efficacy of TGT in CIA mice (A) Plasma TNF-α and IL-6 levels in CIA mice after gavage with 15, 30, and 45 mg/kg TGT suspension or vehicle for 1 week. Data are mean ± SD (n = 5). *p < 0.05 (one-way ANOVA with Bonferroni post hoc test) (B) mRNA levels of TNF-α, IL-6, COX-2, and iNOS in CIA mice after gavage with 15, 30, and 45 mg/kg TGT suspension or vehicle for 1 week. Data are mean ± SD (n = 5). *p < 0.05 (one-way ANOVA with Bonferroni post hoc test) (C) Paw sizes in CIA mice before and after gavage of TGT. Data are mean ± SD (n = 5). *p < 0.05 (one-way ANOVA with Bonferroni post hoc test) (D) H&E staining and histopathological scores. Data are mean ± SD (n = 5). *p < 0.05 (t test) (E) Plasma ALT and AST levels in normal mice treated with TGT (30 mg/kg). Data are mean ± SD (n = 5).

FIGURE 3

SS efficacy depends on dosing time in the CIA mice (A) Plasma TNF-α and IL-6 levels in SS- or vehicle-treated CIA mice at six circadian time points (B) mRNA levels of TNF-α, IL-6, COX-2, and iNOS in SS- or vehicle-treated CIA mice at six circadian time points (C) H&E staining and histopathological scores. Data are mean ± SD (n = 5). *p < 0.05 (two-way ANOVA with Bonferroni post hoc test).

FIGURE 4

TGT efficacy depends on dosing time in the CIA mice (A) Plasma TNF-α and IL-6 levels in TGT- or vehicle-treated CIA mice at six circadian time points (B) mRNA levels of TNF-α, IL-6, COX-2, and iNOS in TGT- or vehicle-treated CIA mice at six circadian time points (C) H&E staining and histopathological scores. Data are mean ± SD (n = 5). *p < 0.05 (two-way ANOVA with Bonferroni post hoc test).

FIGURE 5

Dosing time-dependent pharmacokinetics of SS. Plasma concentration-time curve for (A) brucine (B) strychnine (C) pseudobrucine (D) pseudostrychnine, and (E) dihydroxystrychnine in CIA mice after gavage of SS extract (40 mg/kg) at ZT6 or ZT18. Data are mean ± SD (n = 5). *p < 0.05 (t test).

FIGURE 6

Dosing time-dependent pharmacokinetics of TGT. Plasma concentration-time curve for (A) triptolide and (B) celastrol in CIA mice after gavage of TGT suspension (30 mg/kg) at ZT2 or ZT14. Data are mean ± SD (n = 5). *p < 0.05 (t test).

FIGURE 7

Brucine and strychine inhibit TNF-α, IL-6, COX-2, and iNOS expression in FLS cells (A) Effects of brucine and strychnine at indicated concentrations on the viability of FLS cells (B) Effects of brucine and strychnine (50 μg/ml) on the production of TNF-α and IL-6 in FLS cells. Data are mean ± SD (n = 5). *p < 0.05 (t test) (C) Effects of brucine and strychnine (50 μg/ml) on TNF-α, IL-6, COX-2, and iNOS mRNAs in FLS cells. Data are mean ± SD (n = 5). *p < 0.05 (t test).

FIGURE 8

Triptolide inhibits TNF-α, IL-6, COX-2, and iNOS expression in FLS cells (A) Effects of triptolide at indicated concentrations on the viability in FLS cells (B) Effects of triptolide (6.25 ng/ml) on the production of TNF-α and IL-6 in FLS cells. Data are mean ± SD (n = 5). *p < 0.05 (t-test) (C) Effects of triptolide (6.25 ng/ml) on TNF-α, IL-6, COX-2, and iNOS mRNAs in FLS cells. Data are mean ± SD (n = 5). *p < 0.05 (t test).