This study demonstrates for the first time that RJ has beneficial effects on the colon of rats with acetic acid-induced colitis. Introduction of acetic acid into the colon lumen induced gross lesions in the mucosal part of the intestine and caused typical colitis damage, which was confirmed histomorphometrically by significant increases in diarrhoea, congestion and swelling.18
Pronounced destructive changes associated with ulcerative colitis and haemorrhages were also observed in the colon of rats with acetic acid-induced colitis.
Treatment of colitic rats with an oral dose of RJ gave a degree of recovery from acute colitis. The anti-colitogenic effects of RJ could be attributed to improvement of the antioxidant status of the animals due to an increase in mucin content of the colon mucosa.21
Polyphenolic compounds in their many forms are the main components responsible for the functional properties associated with many foods, such as antioxidant capacity22,23
and anti-inflammatory capacity.24
RJ contains polyphenolic compounds collected by bees from the plants where they gather nectar.25
suggested that Nigella sativa
oil could protect the gastric mucosa against ethanol-induced ulcer. Kanbur et al.4
reported that RJ protects against liver damage induced by paracetamol.
RJ has been shown to exhibit anti-inflammatory, DNA-protective,27
effects in experimental animals. Hamerlinck30
reported that RJ exhibited immunomodulatory properties by stimulating antibody production and immunocompetent cell proliferation in mice or by depressing humoral immune functions in rats. Another report indicated that the protection imparted by RJ ingestion could be partly attributed to the presence of neopterin in RJ.30
The protection afforded by RJ against the immunosuppression produced by increased PGE2 levels has been demonstrated in studies in vivo31
and in vitro
El-Nekeety et al.9
found a potential protective effect of RJ against the toxic hazards of fumonisins. Kamakura et al.32
reported that RJ in the diet decreased the gene expression of cytochrome P450 4A14 (CYP4A14) enzymes and detoxifying enzymes, which catalyse peroxidation of endogenous lipids, and increased the gene expression of glutathione S-transferase and glutathione peroxidase.
Ethanol has been proven to cause gastric damage, an effect confirmed histomorphometrically by significant increases in the number of MC and gastric erosions.33
In the present study, acetic acid-induced colitis caused pronounced destructive changes associated with haemorrhage in the colon of affected rats, as well as increasing number of MC ( C). The ulcerative erosions in colon tissues of rats with acetic acid-induced colitis decreased when the animals were treated with RJ ( D). In addition, RJ prevented any increase in the number of MCs. Oral treatment with an aqueous solution of RJ (150 mL kg−1
) demonstrated a good level of colitis protection.
These findings are in good agreement with recent results presented by El-Dakhakhny et al.
and Kanter et al.
who found that Nigella sativa
had a gastroprotective action in an ethanol-induced ulceration model.
Gebbers et al.35
observed an increase in the number of IgE positive plasma cells and the appearance of intraepithelial MCs in patients with rectal spirochaetosis. Morris et al.36
suggested that MCs numbers increased in inflamed tissues 3–4 weeks after colitis induction. In other studies, an increased MC count in the 5–20 day period37
and an elevated MC protease-2 (RMPC-2) level at 3 weeks were reported in colonic tissue taken from TNBS rats.38
Xu et al.37
reported that MC numbers in the colon of Sabra rats with TNBS-induced colitis were lower during the first five days after induction.
As a result, while acetic acid application caused damage to the colon mucosa of rats, treatment with RJ was found to diminish the harmful effects of acetic acid. Although it has been considered that it might exert the benefits through its antioxidant features, the exact mechanism of effect is yet unknown. In conclusion, it could be suggested that the efforts to focus on the effect mechanism/s of RJ and other traditional medicinal supplements may provide new opportunities for the development of useful drugs.