Effect of Pycnogenol® on an experimental rat model of allergic conjunctivitis

Allergic conjunctivitis (AC) is a frequent and challenging disease in ophthalmology practice. Cell protective effect of Pycnogenol® (PYC) depends on its antioxidant and anti-inflammatory properties. The aim of the study is to investigate the effect of PYC on an experimental AC model.

Ovalbumin and Al(OH)₃ were given seven times intraperitoneally (i.p.) every other day and ovalbumin installed everyday directly on conjunctiva to create an AC rat model. Then, PYC (3 or 10 mg/kg i.p.) was applied in the study groups. Control rats were given adjuvant Al(OH)₃ i.p. and topical saline on conjunctiva. A negative control group in which only PYC (10 mg/kg/7 days) was administered i.p. and an AC positive control group which have been given dexamethasone (1 mg/kg/7 days) was created. Mast cells were counted with a microscope; histological evaluation was performed with H-E and toluidine blue, mast cell tryptase, and TNF-α and TGF-β staining.

Pycnogenol treatment alone did not show any detrimental effect. Mast cell count (MCC) decreased in both dexamethasone and 10 mg/kg given PYC treatment groups compared to positive control group and these results were statistically significant (MCC 1.85 ± 0.69, p < 0.001; 2.42 ± 0.53, p = 0.003). Negative staining with TGF-β and weak focal staining with TNF-α were the common findings of dexamethasone and PYC treatment groups.

The animal model of AC was successfully developed by using aforementioned way. PYC is a safe herbal product and it has alleviated the findings of ovalbumin-induced AC-similar to dexamethasone-histologically in this experimental model. These results are promising for the future of AC treatment.