IntroductionClinical and preclinical studies have shown that supplementation with ω-3 polyunsaturated fatty acids (ω-3 PUFAs) reduce joint destruction and inflammation present in rheumatoid arthritis (RA). However, the effects of individual ω-3 PUFAs on chronic arthritic pain have not been evaluated to date. Thus, our aim in this study was to examine whether purified docosahexaenoic acid (DHA, an ω-3 PUFA) reduces spontaneous pain-related behavior and knee edema and improves functional outcomes in a mouse model of knee arthritis.MethodsUnilateral arthritis was induced by multiple injections of Complete Freund’s Adjuvant (CFA) into the right knee joints of male ICR adult mice. Mice that received CFA injections were then chronically treated from day 15 until day 25 post–initial CFA injection with oral DHA (10, 30 and 100 mg/kg daily) or intraarticular DHA (25 and 50 μg/joint twice weekly). Spontaneous flinching of the injected extremity (considered as spontaneous pain-related behavior), vertical rearing and horizontal exploratory activity (considered as functional outcomes) and knee edema were assessed. To determine whether an endogenous opioid mechanism was involved in the therapeutic effect of DHA, naloxone (NLX, an opioid receptor antagonist, 3 mg/kg subcutaneously) was administered in arthritic mice chronically treated with DHA (30 mg/kg by mouth) at day 25 post–CFA injection.ResultsThe intraarticular CFA injections resulted in increasing spontaneous flinching and knee edema of the ipsilateral extremity as well as worsening functional outcomes as time progressed. Chronic administration of DHA, given either orally or intraarticularly, significantly improved horizontal exploratory activity and reduced flinching behavior and knee edema in a dose-dependent manner. Administration of NLX did not reverse the antinociceptive effect of DHA.ConclusionsTo the best of our knowledge, this report is the first to demonstrate DHA’s antinociceptive and anti-inflammatory effects as individual ω-3 PUFAs following sustained systemic and intraarticular administration in a mouse model of CFA-induced knee arthritis. The results suggest that DHA treatment may offer a new therapeutic approach to alleviate inflammation as well as a beneficial effect on pain-related functional disabilities in RA patients.

Preclinical Research & Development The combination of nonsteroidal anti-inflammatory drugs (NSAIDs) with herbal products having analgesic and anti-inflammatory effects may increase their beneficial effects and limit their side effects. In this study, the effects of an interaction between α-bisabolol and the NSAID, diclofenac on nociception (formalin test), inflammation (paw inflammation produced by carrageenan) and gastric injury in rat was assessed. Diclofenac, α-bisabolol, or diclofenac-α-bisabolol combinations produced antinociceptive and anti-inflammatory effects in rat (p < .05). The systemic administration of diclofenac, but not α-bisabolol, produced gastric damage while the diclofenac-α-bisabolol combinations produced limited gastric damage. Effective dose (ED ) values were determined for each individual drug and analyzed isobolographically. The theoretical ED values for the antinociceptive (98.89 mg/kg) and the anti-inflammatory (41.2 mg/kg) effects differed from the experimental ED values (antinociception: 38.7 mg/kg and anti-inflammation: 13.4 mg/kg). We concluded that the interactions between diclofenac and α-bisabolol are synergistic. These data suggest that the diclofenac-α-bisabolol combinations can interact to produce minor gastric damage, thereby offering a safer therapeutic alternative for the clinical management of inflammation and/or inflammatory pain.

No abstract

No abstract

No abstract