Full Length Research Paper

Study of the immunomodulatory and anti-inflammatory effects of evening primrose oil in adjuvant arthritis

*Manal F. Ismail, Shohda A. El-Maraghy, Nermin A.H. Sadik

Biochemistry Department, Faculty of Pharmacy, Cairo University, Cairo, Egypt.
 

*Corresponding author. E-mail: manalfouad1@yahoo.com. Fax: 00202 3635140.

Accepted 18 March 2008

   Abstract

The present study was carried out to evaluate the anti-arthritic nature of evening primrose oil (EPO) rich in γ-linolenic acid (GLA), on adjuvant-induced arthritic rats. Results were compared to those of diclofenac sodium, a reference standard non-steroidal anti-inflammatory drug. Arthritis was induced by subcutaneous injection of complete Freund’s adjuvant (CFA) in the right hind paw of male Wistar rats. EPO (5 g/kg b.w.) was orally administered from day 0 till day 28, while diclofenac sodium (5 mg/kg b.w.) was orally given from day 10 to day 28 after adjuvant injection. In the arthritic group, the results revealed significant decrease in body weight together with increased spleen weight, increase in serum immunoglobulin G (IgG), immunoglobulin M (IgM) and tumor necrosis factor-α (TNF-α) levels whereas  serum interleukin-4 (IL-4) level was decreased. Serum N-acetyl-β-D-glucosaminidase (NAG) and β-glucuronidase enzyme activities were also elevated. Splenic antioxidant status was suppressed as manifested by increased malondialdehyde (MDA) level, decreased glutathione (GSH) content along with decreased enzymatic activity of glutathione peroxidase (GSHPx), glutathione reductase (GR) and glutathione-S-transferase (GST). Moreover, the splenic activity of the pathophysiological enzymes, γ-glutamyltransferase (γ-GT) and lactate dehydrogenase (LDH) was enhanced. Oral administration of EPO exerted a significant elevation in serum IgG and IgM levels. In addition, normalization of body weight, serum IL-4 and TNF-α levels together with serum NAG, β-glucuronidase and splenic LDH enzyme activities were observed. It could be suggested that administration of plant oils rich in GLA may provide a way to modulate the inflammatory response through alteration of certain inflammatory indices.

Key words: Adjuvant-induced arthritis, evening primrose oil, immunoglobulins, IL- 4, TNF-α, rat.