Heat-Shock Protein Synthesis in Chicken Macrophages: Influence of In Vivo and In Vitro Heat Shock, Lead Acetate, and Lipopolysaccharide

Abstract

Synthesis of heat-shock proteins (HSP) in chicken macrophages, in response to thermal and nonthermal stressors, was determined. Cornell K-strain 6-wk-old White Leghorn females were injected with Sephadex and approximately 42 h later subjected to elevated temperatures in order to achieve a core body temperature (CBT) of 44 C. Peritoneal macrophages were isolated at 30 and 60 min after heat treatment. A parallel group of chickens, maintained at the normal CBT of 41C, was used as controls and peritoneal macrophages were isolated after 60 min of treatment. For in vitro study of HSP response, cells of a chicken macrophage cell line (MQ-NCSU) were subjected to 45 C ambient temperature to produce heat shock (HS, thermal stress), lipopolysaccharide (LPS, 15 μg), and lead acetate (nonthermal stress) exposure for varying time periods. The HSP profiles of macrophages following various treatments were determined by one- and two-dimensional gel electrophoresis. The results showed that macrophages isolated from the 44 C CBT group synthesized HSP90, HSP70, HSP23, and a heat-inducible P32 protein. This HSP synthesis profile was similar to the HSP expression by MQ-NCSU cells exposed in vitro to 45 C conditions. Exposure to MQ-NCSU cells to lead acetate induced the same four proteins previously expressed by macrophages after in vivo or in vitro heat treatment. Two-dimensional analysis of lysates from cells treated with LPS, HS, or LPS plus HS treatments revealed a doublet protein molecule (70a and 70b) with identical molecular mass of 70 kDa. However, the pI value (isoelectric point) of 70b was higher (5.1) than that of 70a, which, along with HSP90 and HSP23, focused more toward the acidic side with a pI value of less than 4.6. The present study is the first to report pI profiles of chicken macrophage HSP. The in vitro and in vivo studies suggest that chicken macrophages respond to thermal and nonthermal stressors by producing similar kinds of “stress proteins”.