Search

The aim of the present study was to assess recovery from hematopoietic and gastrointestinal damage by Ex-RAD®, also known as ON01210.Na (4-carboxystyryl-4-chlorobenzylsulfone, sodium salt), after total body radiation. In our previous study, we reported that Ex-RAD, a small-molecule radioprotectant, enhances survival of mice exposed to gamma radiation, and prevents radiation-induced apoptosis as measured by the inhibition of radiation-induced protein 53 (p53) expression in cultured cells. We have expanded this study to determine best effective dose, dose-reduction factor (DRF), hematological and gastrointestinal protection, and in vivo inhibition of p53 signaling. A total of 500 mg/kg of Ex-RAD administered at 24 h and 15 min before radiation resulted in a DRF of 1.16. Ex-RAD ameliorated radiation-induced hematopoietic damage as monitored by the accelerated recovery of peripheral blood cells, and protection of granulocyte macrophage colony-forming units (GM-CFU) in bone marrow. Western blot analysis on spleen indicated that Ex-RAD treatment inhibited p53 phosphorylation. Ex-RAD treatment reduces terminal deoxynucleotidyl transferase mediated dUTP nick end labeling assay (TUNEL)-positive cells in jejunum compared with vehicle-treated mice after radiation injury. Finally, Ex-RAD preserved intestinal crypt cells compared with the vehicle control at 13 and 14 Gy. The results demonstrated that Ex-RAD ameliorates radiation-induced peripheral blood cell depletion, promotes bone marrow recovery, reduces p53 signaling in spleen and protects intestine from radiation injury.

The effect of lipopolysaccharide (LPS) on cardiac protein kinase C (PKC) activation and cardiac depression was evaluated. Guinea pigs (n = 44) received intraperitoneal injections of saline or Escherichia coli LPS (2 mg/kg). Left atria were harvested 16 h later and suspended in oxygenated low calcium (1 mM) (n = 24) or high calcium (5 mM) (n = 20) 30°C Krebs-Henseleit buffer. Atria were treated with H-7 (n = 23), a PKC inhibitor, or vehicle (n = 21). Contractile responses to changes in preload and stimulating frequency, in the resting and potentiated states, and to escalating doses of phenylephrine were measured. PKC activation in ventricular muscle was also determined. LPS activated ventricular PKC (p< .05) but treatment with H-7 failed to reverse LPS-induced atrial dysfunction in the low calcium buffer. Contractile function in the potentiated state indicated that LPS appears to interfere with calcium release from the sarcoplasmic reticulum (SR). The contractile response to phenylephrine was markedly attenuated in atria harvested from endotoxic animals. These data indicate that LPS-induced cardiac depression is mediated, in part, by alterations in SR calcium release. LPS activates cardiac PKC but a causal relationship among LPS, PKC, and cardiac dysfunction remains to be established.