The allergic inflammatory reaction in neonatal streptozotocininduced diabetic rats: evidence of insulin resistance and microvascular dysfunction

OBJECTIVE

To investigate the allergic reaction in neonatal streptozotocin (nSTZ)-induced diabetes mellitus.

MATERIAL

Male newborn Wistar rats were made diabetic by the injection of streptozotocin (160 mg/kg, i. p.) and used 8 weeks thereafter.

TREATMENT

Animals were sensitized against ovalbumin (OA, 50 microg and Al(OH)3, 5 mg, s. c.) and challenged 14 or 21 days thereafter.

METHODS

OA-induced airway inflammation and OA-induced pleurisy models were used to investigate leukocyte migration (total and differential leukocyte counts) and lung vascular permeability (Evans blue dye extravasation).

RESULTS

nSTZ-diabetic rats presented glucose intolerance and insulin resistance. Relative to controls, nSTZ rats exhibited a 30% to 50% reduction in lung vascular permeability. Leukocyte infiltration in both models of allergen-induced inflammation, and number of pleural mast cells did not differ between groups.

CONCLUSIONS

Data suggest that the reduction of allergic inflammatory reactions in nSTZ rats is restricted to microvascular dysfunctions and associated, probably, with insulin resistance in lung microvascular endothelium.

Pharmacological study of anti-allergic activity of Syzygium cumini (L.) Skeels

Myrtaceae is a plant family widely used in folk medicine and Syzygium and Eugenia are among the most important genera. We investigated the anti-allergic properties of an aqueous leaf extract of Syzygium cumini (L.) Skeels (SC). HPLC analysis revealed that hydrolyzable tannins and flavonoids are the major components of the extract. Oral administration of SC (25-100 mg/kg) in Swiss mice (20-25 g; N = 7/group) inhibited paw edema induced by compound 48/80 (50% inhibition, 100 mg/kg; P <or= 0.05) and, to a lesser extent, the allergic paw edema (23% inhibition, 100 mg/kg; P <or= 0.05). SC treatment also inhibited the edema induced by histamine (58% inhibition; P <or= 0.05) and 5-HT (52% inhibition; P <or= 0.05) but had no effect on platelet-aggregating factor-induced paw edema. SC prevented mast cell degranulation and the consequent histamine release in Wistar rat (180-200 g; N = 7/group) peritoneal mast cells (50% inhibition, 1 microg/mL; P <or= 0.05) induced by compound 48/80. Pre-treatment of BALB/c mice (18-20 g; N = 7/group) with 100 mg/kg of the extract significantly inhibited eosinophil accumulation in allergic pleurisy (from 7.662 +/- 1.524 to 1.89 +/- 0.336 x 10(6)/cavity; P <= 0.001). This effect was related to the inhibition of IL-5 (from 70.9 +/- 25.2 to 12.05 +/- 7.165 pg/mL) and CCL11/eotaxin levels (from 60.4 +/- 8.54 to 32.8 +/- 8.4 ng/mL) in pleural lavage fluid, using ELISA. These findings demonstrate an anti-allergic effect of SC, and indicate that its anti-edematogenic effect is due to the inhibition of mast cell degranulation and of histamine and serotonin effects, whereas the inhibition of eosinophil accumulation in the allergic pleurisy model is probably due to an impairment of CCL11/eotaxin and IL-5 production.

Down-regulation of mast cell activation and airway reactivity in diabetic rats: role of insulin

Hormones play a modulating role in allergic inflammation. An inverse relationship between atopy and diabetes mellitus was reported. The mechanisms regulating this interaction are not completely understood. This study examined whether insulin influences mast cell activation following antigen challenge in rats. The experimental design included alloxan-induced diabetic rats and matching controls. Experiments were performed 30 days after alloxan injection. The animals were sensitised by s.c. injection of ovalbumin (OA) and aluminium hydroxide. OA-induced airway contraction, morphometric analysis of airway mast cells and tissue histamine quantification were evaluated in the isolated main bronchus and intrapulmonary bronchus upon exposure to antigen in vitro. Relative to controls, a reduced contraction to OA was observed in bronchial segments isolated from diabetic rats. This was accompanied by a 50% reduction in the number of degranulated mast cells and in histamine release. A complete recovery of the impaired responses was observed under the influence of insulin. In conclusion, the data suggested that insulin might modulate the controlling of mast cell degranulation; therefore, the early-phase response to antigen provocation, which represents a new insight into a better understanding of the mechanisms, accounted for the decreased risk of asthma among type-1 diabetic patients.