Effect of Pycnogenol® on an Experimental Rat Model of Allergic Conjunctivitis

Graefes Arch Clin Exp Ophthalmol. 2018 Jul;256(7):1299-1304. doi: 10.1007/s00417-018-3988-7. Epub 2018 Apr 20.


Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: Allergy; Conjunctivitis; French maritime pine; Pycnogenol®; Rat.

MeSH terms

  • Adjuvants, Immunologic / administration & dosage
  • Administration, Topical
  • Animals
  • Biomarkers / metabolism
  • Conjunctiva
  • Conjunctivitis, Allergic / drug therapy*
  • Conjunctivitis, Allergic / metabolism
  • Conjunctivitis, Allergic / pathology
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Flavonoids / administration & dosage*
  • Immunohistochemistry
  • Male
  • Plant Extracts
  • Rats
  • Transforming Growth Factor beta / metabolism*
  • Treatment Outcome


  • Adjuvants, Immunologic
  • Biomarkers
  • Flavonoids
  • Plant Extracts
  • Transforming Growth Factor beta
  • pycnogenols