Improvement of Resveratrol Effects When Combined with Rice Oil in Rat Models of Inflammation

Chemical constituents, biological activities and anti-rheumatoid arthritic properties of four citrus essential oils

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease with predominant synovitis that has no complete cure or preventive treatment. Citrus essential oils, used in natural fragrances, contain a variety of functional ingredients that are worthy of investigation for their potential as natural anti-inflammatory drug sources. In this study, essential oils were hydro distilled from the peels of four citrus species: Citrus sinensis (L.) Osbeck (CSEOs), Citrus paradisi Macfad. (CPEOs), Citrus limon (L.) Osbeck (CLEOs) and Citri Reticulatae Pericarpium (CREOs). Altogether, 81 compounds were identified using gas chromatography-mass spectrometry (GC-MS), of which d-limonene (17.96%-94.66%) was an abundant component of all four oils. The stable 1,1-diphenyl-2-pyrrole hydrazine (DPPH) free radical test showed that all four essential oils had excellent antioxidant properties (IC₅₀ , 0.76-13.86 μg/mL). Furthermore, the oils remarkably increased the first G1 phase of the cell cycle, which inhibited the pro-inflammatory factor expression. An immunohistochemical analysis indicated that the four essential oils inhibited the expression of tumor necrosis factor-α and cyclooxygenase-2 and they exhibited anti-inflammatory activity in a rat model that was similar to that of the common drug, Ibuprofen. These results show that the CSEOs, CPEOs, CLEOs, and CREOs have significant antirheumatic activities and thus have great potential in developing functional food or drugs for treating RA.

Central and peripheral effects of environmental enrichment in a mouse model of arthritis

This study analyzed whether environmental enrichment (EE) modulates the nociceptive and inflammatory responses in the mouse model of arthritis induced by Complete Freund's Adjuvant (CFA). Ninety male mice (C57BL/6-JUnib, 4-weeks-old; 20-25 g) were distributed into EE and standard (SE) groups. For EE, mice were kept in bigger cages using an alternation of materials to chew (wood and paper), for nesting (cotton), to use as hiding places (plastic tunnels), and for voluntary exercise (wheel running). Arthritis was induced by an injection of CFA (50 μL) into the right hind paw or saline solution in the control group. Separate groups received the anti-inflammatory drug dexamethasone (0.5 mg/kg; every 48 h). Inflammatory and pain measurements were performed from 1 to 35 days after CFA administration. EE per se reduced the acute paw edema formation and arthritis scores. The serum levels of tumor necrosis factor (TNF) were undetectable in any experimental groups. EE diminished the immunopositivity for the microglia marker IBA1 in the pre-frontal cortex, with slight changes for hippocampal GFAP-positive activated astrocytes. Finally, EE induced a marked increment of brain-derived nerve factor (BDNF) expression in the hippocampus, an effect that was fully prevented by dexamethasone. These data bring novel evidence on the peripheral and central effects of EE in a mouse arthritis model.

The pharmacological assessment of resveratrol on preclinical models of rheumatoid arthritis through a systematic review and meta-analysis

Resveratrol/RES (3,5,4'-trihydroxy-trans-stilbene) is a natural compound found in many food items and red wine, which exhibits pleiotropic biological effects. Several preclinical studies evaluating the efficacy of RES in animal models of rheumatoid arthritis (RA) have been conducted, but the diversity of the experimental conditions and of their outcomes preclude definitive conclusions about RES's efficacy. We, therefore, performed a meta-analysis to assess its efficacy in mitigating experimental RA. We searched three databases until January 2021 and used the random-effects model for drawing inferences. Eighteen studies involving 544 animals were used in this study. Pooled analysis showed that experimental RA causes paw swelling (Hedge's g = 9.823, p = 0.000), increases polyarthritis score and arthritis index, and RES administration reduces paw volume (Hedge's g = -2.550, p = 0.000), polyarthritis score, and arthritis index besides amelioration in the histopathological score and cartilage loss. RA is accompanied by increased oxidative stress due to high malondialdehyde (MDA) level (p < 0.001) and low superoxide dismutase (SOD) activity (p = 0.002), and RES reduced MDA level (p < 0.001) and increased SOD activity (p < 0.001). Experimental RA exhibited an increase in pro-inflammatory cytokines viz. tumor necrosis factor (TNF)-α (p < 0.001), interleukin (IL)-6 (p = 0.002), and IL-1 (p < 0.001); however, insufficient quantitative data precluded us from assessing changes in the anti-inflammatory cytokine, IL-10. In experimental RA, RES decreased TNF-α (p < 0.001), IL-6 (p < 0.001) and IL-1 (p = 0.001) and increased IL-10. This meta-analysis suggests that RES can be a clinically effective therapy for RA, pending clinical trials.