Penetrability of interleukin-1β and its effect on the concentration of tumor necrosis factor-α and interleukin-6 in the aqueous humor of rabbits treated with interleukin-1β

Background Interleukin (IL)-1β may effectively decrease introcular pressure (IOP) when administered bysubconjunctival injection in normal rabbit.However,IL-1β is a large molecular agent and an inflammation factor.The aimof this study was to evaluate the penetrability of IL-1β,and the concentrations of both tumor necrosis factor (TNF)-α andIL-6 in the aqueous humor of normal rabbits treated with IL-1β.Methods A total of 170 rabbits were used in the study and were assigned to several different treatment groups asfollows:125 of the rabbits were assigned to two groups.In one group,33 rabbits were injected subconjunctivally withIL-1β and 39 were injected with saline alone.In the other group,27 rabbits were given eye drops containing IL-1β (400ng/ml) and 26 were given saline alone.Aqueous humor (AH) was drawn and the concentration of IL-1β within the fluidmeasured.The IOP was measured in another six rabbits after administration of eye drops containing IL-1β (400 ng/ml).Afurther 20 rabbits were assigned to 3 groups as follows:eight untreated normal controls;six injected subconjunctivallywith IL-1β;and six injected subconjunctivally with saline alone.AH was drawn and the concentration of TNF-α in the fluidwas measured.Another 19 rabbits were assigned to 3 groups as follows:seven untreated normal controls;and six injectedsubconjunctivally with IL-1β;and six injected subconjunctivally with saline alone.AH was drawn and the concentration ofIL-6 in the fluid measured.Measurement of cytokine concentration was by radio-immunoassay in all cases.Results The IL-1β concentration in the AH was higher in those animals in which it had been administeredsubconjunctivally (P<0.01).The IL-1β concentration in the AH of the animals given eye drops was almost the same asthat in the controls (P>0.05).The administration of IL-1β in the form of eye drops had little effect upon IOP reduction.Lower TNF-α concentrations were seen in the AH after the subconjunctival administration of IL-1β,but the concentrationof IL-6 was the same as in the normal controls.Conclusions IL-1β shows good corneal penetrability after subconjunctival injection into normal rabbit eyes.The IOPreduction induced by IL-1β is unlikely be associated with an inflammatory response.