The
neuropeptide vasoactive intestinal peptide (VIP) is anti-inflammatory and protective in the immune and nervous systems, respectively. This study demonstrated in corneal endothelial (CE) cells injured by severe oxidative stress (1.4 mM H(2)O(2)) in bovine corneal organ cultures that VIP pre-treatment (0, 10(-10), 10(-8), and 10(-6)
M; 15 min), in a VIP concentration-dependent manner, switched the
inflammation-causing
necrosis to
inflammation-neutral apoptosis (showing
annexin V-binding,
chromatin condensation, and DNA fragmentation) and upheld
ATP levels in a VIP antagonist (SN)
VIPhyb-sensitive manner, while up-regulated
mRNA levels of the anti-apoptotic Bcl-2 and the
differentiation marker N-cadherin in a
kinase A inhibitor-sensitive manner. As a result, VIP, in a concentration-dependent and VIP antagonist-sensitive manners, promoted long-term CE cell survival.
ATP levels, a determining factor in the choice of apoptosis versus
necrosis, measured after VIP pre-treatment and 0.5 min post-H(2)O(2) were 39.6 +/- 3.3, 50.8 +/- 6.2, 60.1 +/- 4.8, and 53.6 +/- 5.3 pmoles/microg
protein (mean +/- SEM), respectively (p < 0.05, anova). VIP treatment alone concentration-dependently increased levels of
N-cadherin (Koh et al. 2008), the phosphorylated cAMP-responsive-
element binding protein and Bcl-2, while 10(-8) M VIP, in a VIP antagonist (SN)
VIPhyb-sensitive manner, increased
ATP level by 38% (p < 0.02) and decreased
glycogen level by 32% (p < 0.02). VPAC1 (not
VPAC2) receptor was expressed in CE cells. Thus, CE cell VIP/VPAC1 signaling is both anti-inflammatory and protective in the corneal endothelium.