Detrimental effect of the proteasome inhibitor, bortezomib in bacterial superantigen-and lipopolysaccharide-induced systemic inflammation

Bacterial superantigen (BSAg)-induced toxic shock syndrome (TSS) and bacterial lipopolysaccharide (LPS)-induced shock are characterized by severe systemic inflammation. As nuclear factor B (NFB) plays an important role in inflammation and bortezomib, a proteasome inhibitor widely used in cancer chemotherapy, is a potent inhibitor of NFB activation, we evaluated the therapeutic and prophylactic use of bortezomib in these conditions using murine models. Bortezomib prophylaxis significantly reduced serum levels of many cytokines and chemokines induced by BSAg. However, at 3 hours, serum level of TNF-a, an important cytokine implicated in TSS, was significantly reduced but not abolished. At 6 hours, there was no difference in the serum TNF-a levels between bortezomib treated and untreated mice challenged with staphylococcal enterotoxin B (SEB). Paradoxically, all mice treated with bortezomib either before or after BSAg challenge succumbed to TSS. Neither bortezomib nor BSAg was lethal if given alone. Serum biochemical parameters and histopathological findings suggested acute liver failure as the possible cause of mortality. Liver tissue from SEB-challenged mice treated with bortezomib showed a significant reduction in NFB activation. Because NFB-dependent antiapoptotic pathways protect hepatocytes from TNF-α-induced cell death, inhibition of NFB brought forth by bortezomib in the face of elevated TNF-α levels caused by BSAg or LPS is detrimental.