OVEREXPRESSION OF ??B CRYSTALLIN IN THE GASTROINTESTINAL TRACT OF THE NEWBORN PIGLET AFTER HYPOXIA

Abstract

Newborn animals are particularly sensitive to hypoxic stress. Oxygen is spared for sensitive tissues, including brain and heart. Scarce information is available concerning the molecular effects of hypoxia in the gastrointestinal tract (GIT). Moreover, stress protein expressions, including heat shock proteins (HSP), are still poorly documented in the GIT. Our objective was to determine the possible effect of hypoxia on HSP expression at birth. After western blotting, alphaB crystallin, HSP 27, and HSP 70 expressions were determined in newborn controls and piglets exposed to 1 or 4 h hypoxia (5% O2, 95% N2) allowed to recover from 1 to 68 h. Cytosol and nuclei were also separated and the extracts were tested for HSF1 and alphaB crystallin expressions. Surprisingly, alphaB crystallin was overexpressed in the stomach and colon in animals submitted to hypoxia, whereas HSP 27 and HSP 70 expression remained stable. Increases and return to basal levels in HSF1 and alphaB crystallin were simultaneously observed in the unique nuclear compartment. To our knowledge, the present study is the first to demonstrate the oxygen dependency of an HSP in the GIT, particularly in the colon in newborn piglets. The kinetics of alphaB crystallin overexpression after hypoxia parallels the activation of HSF1. This observation possibly indicates a correlation between this factor and alphaB crystallin after hypoxia. Taken together, the present results open the field of wide investigation about the specific response of this low-molecular-weight HSP and its possible involvement in pathological states in the GIT such as stomach and colon.