The role of endothelin peptides in endotoxine induced experimetal uveitis model in mice eye

Endothelin-1 (ET-1) is an endogenous vasoactive peptide that is considered among the most potent vasoconstrictor substances known. Endothelins and their receptors have been shown to be present in the eye and it is reported that they influence aqueous protein concentration (APC) and play role in etiopathogenesis of uveitis.In this study, we investigated the serum and humor aqueous (HA) ET-1 levels and APC changes in an endotoxin-induced experimental uveitis model in mice. The influence of intraperitoneally injected ETA receptor antagonist (BQ123), non-selective ET-1 antagonist (Bosentan), non-selective nitric oxide sentase inhibitor (L-NAME) and non-selective cyclooxygenase inhibitor (indomethacin) on those parameters were also assessed. In addition, the severity of uveal inflammation were examined histopathologically.In this study, 96 eyes of 48 mice (8-week-old, 25 g) were examined. The mice were evaluated in eight groups. The 1st group was the control group and no procedure was done. In the 2nd group, experimental uveitis model was induced by intraperitoneal injection of lipopolysaccharide (LPS, S. Thphmirium, 50?g/0.1ml). In the 3rd group, both LPS and BQ123 (25?gr/0.05ml) was injected intraperitoneally in the same time. In the 4th group, both LPS and bosentan (100?gr/0.2ml) were injected in the same manner. In the 5th group, both LPS and L-NAME (10mg/kg/0.2ml) were injected in the same manner. In the 6th group, LPS, Bosentan and L-NAME were injected in the same manner. In the 7th group,both LPS and indomethacin (10mg/kg/0.2ml) were injected in the same manner. In the 8th group, LPS, indomethacin and bosentan were injected in the same manner. 24 hours after injections, serum and HA samples (right eyes) were drawn. Serum and HA ET-1 levels were measured by quantitative sandwich enzyme immunassay technique. APC was measured by modified Lowry method. The animals were sacrified after the collection of samples and than the left eyes were enucleated and histopathological changes were examined.The control group, mean levels of serum and HA ET-1 were 95,90±32,53 pg/ml and 144,03±44,71 pg/ml respectively. Mean levels of APC were 270,87±149,09 pg/ml in the control group. LPS injection, inceased the levels of serum, HA ET-1 and APC significantly.These levels were, 291,94±74,97 pg/ml (p=0.004), 565,67±376,29 pg/ml (p=0,037) and 783,40±74,43 pg/ml (p=0,004) respectively. Also, severe uveitis was seen histopathologically in the LPS injected mice. Injecting BQ123 inhibited the LPS induced elevation in serum, HA ET-1 levels and APC. Those parameters were, 83,33±37,56 pg/ml (p=0.004), 138,91±63,70 pg/ml (p=0,037) and 525,01±49,23 pg/ml (p=0,037) respectively. Similarly, BQ123 inhibited LPS induced uveitis histopathologically. Bosentan injection could not inhibit, on the contrary, it augmented those parameters, which were, 386,23±176,78 pg/ml (p>0.05), 540,33±214,18 pg/ml (p>0.05) and 1107,10±117,67 pg/ml (p=0,055) respectively. It was also seen that bosentan aggravated the uveitis histopathologically. Injection of L-NAME, decreased the serum ET-1 levels and APK when compared with LPS alone. Those levels were 76,09±23,32 pg/ml (p=0.004) and 544,13±75,52 pg/ml (p=0,004) respectively. L-NAME injection decreased HA ET-1 level which was measured 232,38±114,53 pg/ml (p=0.109) and had no statistical value. LPS induced uveitis was inhibited histopathologically with L-NAME injection coherent with those findings. The combination of L-NAME and bosentan did not alter the LPS induced ET-1 elevation both serum and HA but decreased APC. Those parameters were 256,30±109,68 pg/ml (p>0.05), 469,65±124,80 (p>0.05) and 569,57±81,11 pg/ml (p=0,006) respectively. Indomethacin injection inhibited serum and HA ET-1 levels, 171,31±121,61 pg/ml (p=0.109) and 375,00±243,98 pg/ml (p=0.15) respectively, when compared with those treated LPS alone but those had no statistical value. Mean APC was 322,08±13,05 pg/ml (p=0,004). This parameter and histopathologically LPS induced uveitis were inhibited in idomethacin injected mice. In indomethacin and bosentan combination, mean serum and HA ET-1 levels were 99,94±80,11 pg/ml and 394,95±355,72 pg/ml respectively and had no stastistical value when compared with those treated with indomethacin alone (p>0.05). Histopathologic findings are similar between those groups. In the 8th group mean APC level was 760,41±86,97 pg/ml and higher than 7th (p=0,004)ET-1 is an important mediator in uveitis etiopathogenesis. ETA receptor blockage decreases both serum and HA ET-1 levels and ameliorate LPS induced uveitis. ETB receptor blockage increases both serum and HA ET-1 levels and aggravate uveitis. We think that ET-1 synthesis inhibitors or ETA receptor antagonists may play role in the treatment of uveitis if more studies are done concerning these modalities.