Immunocytochemical detection of the 70-kd heat shock protein in alcoholic liver disease

Exposure of cells to physical (eg, heat) or chemical (eg, alcohol) stress results in increased synthesis of a set of highly conserved polypeptides termed heat shock proteins (HSPs), among which the 70-kd protein (HSP 70) is one of the most consistently inducible and highly conserved. This HSP has adenosine triphosphate-binding properties and is known to associate strongly with cytoskeletal structures that are usually disrupted on injury by heat or alcohol. Some HSPs apparently function as accessories to a nonlysosomal, adenosine triphosphate-dependent proteolytic system that binds and digests away stress-generated abnormal or denatured proteins after their conjugation with ubiquitin, a small HSP. Ubiquitin has been demonstrated immunocytochemically in Mallory bodies, which represent mainly degenerated intermediate filaments accumulated in hepatocytes of alcoholic-diseased liver. We immunostained histologic sections from patients with alcoholic liver disease using a polyclonal antibody raised against HSP 70. Strong diffuse cytoplasmic immunoreactivity was observed in many hepatocytes, including cells without Mallory bodies or fatty degeneration. Positive immunoreactivity for HSP 70 points to a possible involvement of this HSP in the pathogenesis of alcoholic liver disease. It also suggests that immunocytochemical detection of HSP 70 may serve as a more sensitive indicator of hepatocellular injury.