Therapeutic Use of Scoparia dulcis Reduces the Progression of Experimental Osteoarthritis

Abstract

Pain is recognized as one of the main symptoms in knee osteoarthritis and is the main reason why patients seek medical attention. Scoparia dulcis has been popularly used to relieve discomfort caused by various painful conditions. The objective of the study is to evaluate the analgesic and anti-inflammatory effect of the crude extract of S. dulcis, in an experimental model of osteoarthritis. The experiment was performed with Wistar rats divided into 4 groups with 5 animals each: healthy, saline, crude extract, and meloxicam groups. Knee osteoarthritis was induced by intra-articular injection of sodium mono-iodoacetate. First, clinical parameters of pain were assessed at days 0, 5, 10, 15, and 20 after induction. Second, the potential cyclooxygenase inhibition was evaluated, and the cytokines of the synovial fluid were quantified. An in silico test and Molecular Docking tests were performed. A histopathological evaluation was made on articular cartilage with safranin O staining. The results showed that a 15-day treatment with crude extract reduced edema, spontaneous pain, peripheral nociceptive activity, and proinflammatory cytokines in the synovial fluid. The highest inhibition of cyclooxygenase 2 in the crude extract occurred at 50 µg/mL. The crude extract of S. dulcis presents therapeutic potential for the treatment of osteoarthritis due to its anti-inflammatory and anti-nociceptive action.

Keywords: Inflammation; Osteoarthritis; Pain; Scoparia dulcis; Treatment.

Figure 1

Effect of crude extract of S. dulcis on the tactile sensory evaluation using the Von Frey test. Results were expressed as mean ± standard mean error; # difference between healthy group (GS) and saline group (GSAL) in D5 (p < 0.0001), GS and Scoparia dulcis Group (GSD) in D5 (p < 0.0001), GS and meloxicam group (GM) in D5 (p < 0.0001); * difference between GSD and GSAL in D10 (p = 0.0015), D15 (p = 0.0002) and D20 (p < 0.0001); *** difference between GM and GSAL in D10 (p = 0.0004), D15 (p = 0.0016) and D20 (p < 0.0001), using 2-way ANOVA with the multiple comparisons test (p < 0.05).

Figure 2

Effect of crude extract of S. dulcis on the evaluation of motor activity/forced ambulation using the Rotarod test. Results were expressed as mean ± standard mean error; # difference between GS and GSAL in D5 (p < 0.0001), GS and GSD in D5 (p < 0.0001), GS and GM in D5 (p < 0.0001); * difference between the GSD and GSAL in the D20 (p = 0.0061); *** difference between GM and GSAL in the D20 (p < 0.0472), using 2-way ANOVA with the multiple comparisons test (p < 0.05).

Figure 3

Effect of the crude extract of S. dulcis on the assessment of the weight distribution in the hind paws using the weight bearing test. Results were expressed as mean ± standard mean error; # difference between GS and GSAL in D5 (p < 0.0001), GS and GSD in D5 (p < 0.0001) and GS and GM in D5 (p < 0.0001); * difference between GSD and GSAL in D15 (p = 0.0025) and D20 (p = 0.0037); *** difference between GM and GSAL in D15 (p = 0.0062) and D20 (p < 0.0001), using 2-way ANOVA with the multiple comparisons test (p < 0.05).

Figure 4

Effect of the crude extract of S. dulcis on the edematogenic evaluation of the circumference of the knee by the pachymeter. Results were expressed as mean ± standard mean error; # difference between GS and GSAL in D5 (p < 0.0001), GS and GSD in D5 (p < 0.0001) and GS and GM in D5 (p < 0.0001); * difference between GSD and GSAL in D10 (p < 0.0001), D15 (p < 0.0001) and D20 (p < 0.0001); *** difference between GM and GSAL in D10 (p < 0.0001), D15 (p < 0.0001) and D20 (p < 0.0001), using 2-way ANOVA with the multiple comparisons test (p < 0.05).

Figure 5

Effect of crude extract of S. dulcis on the evaluation of spontaneous pain by Mouse Grimace Scale. Results were expressed as mean ± standard mean error; # difference between GS and GSAL in D5 (p < 0.0001), GS and GSD in D5 (p < 0.0001), GS and GM in D5 (p < 0.0001); * difference between GSD and GSAL in D10 (p = 0.0062), D15 (p < 0.0001) and D20 (p < 0.0001); *** difference between GM and GSAL in D10 (p = 0.0068), D15 (p = 0.0003) and D20 (p < 0.0001), using 2-way ANOVA with the multiple comparisons test (p < 0.05).

Figure 6

Percent inhibition of in vitro Cyclooxygenase-1 (COX-1) e Cyclooxygenase-2 (COX-2), induced by the crude extract of S. dulcis, tested in three concentrations: 2 μg/mL, 10 μg/mL, and 50 μg/mL. The data are represented in mean + standard deviation of the means. **** Represents significant differences, with p < 0.0001 comparing inhibition of COX-1 and COX-2.

Figure 7

Total Ion Chromatogram of extract from S. dulcis acquired by LC-ESI-MS (m/z: 100–1500 Da).

Figure 8

Diagram from interactions performed by Suspensaside and Nicotiflorin with COX-2 structure. Black dashed lines represent hydrogens bonds; green dashed lines represent pi-pi interactions and green full lines represent van der Walls interactions. The Figure was generated with PoseView.

Figure 9

Spatial conformation of suspensaside (green) and nicotiflorin (magenta) on the COX-2 active site (PDB 1DDX). Image generated with USCF Chimera.

Figure 10

Effect of crude extract of S. dulcis on classification articular cartilage histology. (A) For articular cartilage, the score 0 represents the surface and morphology of intact cartilage (GS). (B) Score 1, an intact surface with superficial fibrillation (GSD). (C) For score 2 there is already a discontinuity of the articular cartilage (GM) surface. (D) For score 4 (GSAL), the surface has vertical crack-like cracks with erosion areas.