Identification of human cell responses to hexavalent chromium

Hexavalent chromium [Cr(VI)] is a recognized environmental toxin with ubiquitous distribution in industrialized societies. Its concentration in ambient air derives from several sources including but not limited to chemical processes, the burning of fossil fuels and the production of cement. It is a food contaminant because of its deposition into bodies of water. The majority of published studies on the effects of Cr(VI) concern animal models and these studies have shown that it can induce a variety of cytotoxic and genotoxic reactions that affect the immune system. In order to identify the specific cellular impact of Cr(VI) on humans, we studied its effect on protein production and gene expression in human peripheral blood mononuclear cells (PBMC) obtained from both men and women of each major ethnic group including Caucasians, Hispanics, Asians and African-Americans. High-throughput protein profiling using bead-based protein arrays showed a concentration-dependent biphasic effect of Cr(VI) on the expression of many cytokines and chemokines by activated PBMC. High-density oligonucleotide microarray analysis identified several functional families of genes including those involved in immune response, intracellular signaling, cell cycle, apoptosis, RNA transport and binding, organelle organization and biogenesis that were strongly affected by Cr(VI). Cr(VI) suppressed many cellular receptor genes involved in immune response and activated many cell cycle-related and proapoptotic genes. These results defined responses that were unique to Cr(VI). This methodology defined an effective manner for identifying injurious/toxic human exposures to Cr(VI) at the cellular level that may facilitate the identification and monitoring of efficacious treatments for Cr(VI)-related maladies.