Liposomal Delivery of Purified Heat Shock Protein hsp70 Into Rat Pancreatic Islets as Protection Against Interleukin 1β–Induced Impaired β-Cell Function

Abstract

Recently it has been demonstrated that heat shock protein 70 (hsp70) is induced in pancreatic islet cells during prolonged exposure to interleukin 1 beta (IL-1 beta). It is unclear whether this represents a cellular defense against the noxious action of IL-1 beta or whether hsp70 is involved in the suppressive action of the cytokine. To assess the role for hsp70 in isolated islets exposed to IL-1 beta, hsp70 was purified and introduced into cells of isolated rat pancreatic islets via the liposome technique. Delivery of hsp70 was efficient according to immunoblot analysis, but delivered hsp70 disappeared within 16 h. Hsp70-containing liposomes did not affect protein synthesis, insulin secretion, or islet insulin mRNA content. However, when hsp70 liposome-incubated islets were further exposed to IL-1 beta (25 U/ml) for 16 h, these islets released more insulin in response to glucose stimulation and contained more insulin mRNA than islets incubated with control liposomes and subsequently exposed to the cytokine. No protective effect of liposomes containing bovine serum albumin or ovalbumin were observed. We conclude that hsp70 may protect against IL-1 beta-induced impairment of pancreatic beta-cell function.