Expression and secretion of alpha1-proteinase inhibitor are regulated by proinflammatory cytokines in human pancreatic islet cells

Diabetologia. 2005 Aug;48(8):1523-33. doi: 10.1007/s00125-005-1816-1. Epub 2005 Jul 7.


Aims/hypothesis: Alpha1-proteinase inhibitor (alpha1-PI) has been considered a key player in inflammatory processes. In humans, the main production site of alpha1-PI is the liver, but other tissues, including pancreatic islets, also synthesise this molecule. The aims of this study were to assess the islet cell types that produce alpha1-PI, to determine whether alpha1-PI is actually secreted by islet cells, and to assess how its production and/or secretion are regulated.

Methods: Expression of alpha1-PI in human islet cells was assessed by immunofluorescence, electron microscopy and western blotting. Release of alpha1-PI was analysed by reverse haemolytic plaque assay and ELISA. The effects of cytokines on alpha1-PI synthesis and secretion were tested.

Results: Immunofluorescence showed that alpha and delta cells do express alpha1-PI, whereas beta cells do not. By electron microscopy, we demonstrated a colocalisation of alpha1-PI with glucagon and somatostatin within secretory granules. Immunolabelling also revealed localisation of alpha1-PI within the Golgi apparatus, related vesicles and lysosomal structures. The expression of alpha1-PI in islet cells was also demonstrated by western blotting and ELISA of protein extracts. ELISA and reverse haemolytic plaque assay showed that alpha1-PI is secreted into the culture medium. Treatment of islet cells with IL-1beta and oncostatin M for 4 days increased the production and release of alpha1-PI.

Conclusions/interpretation: Our results demonstrate that alpha1-PI is expressed by the alpha and delta cells of human islets, and that proinflammatory cytokines enhance the production and release of this inhibitor.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 1-Methyl-3-isobutylxanthine / pharmacology
  • Anti-Inflammatory Agents / pharmacology
  • Antibodies / pharmacology
  • Blotting, Western
  • Cell Separation
  • Cells, Cultured
  • Cytokines / pharmacology*
  • Dexamethasone / pharmacology
  • Enzyme-Linked Immunosorbent Assay
  • Fluorescent Antibody Technique
  • Hemolytic Plaque Technique
  • Humans
  • Immunohistochemistry
  • Interleukin-1 / pharmacology
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / metabolism*
  • Microscopy, Immunoelectron
  • alpha 1-Antitrypsin / biosynthesis*
  • alpha 1-Antitrypsin / genetics


  • Anti-Inflammatory Agents
  • Antibodies
  • Cytokines
  • Interleukin-1
  • alpha 1-Antitrypsin
  • Dexamethasone
  • 1-Methyl-3-isobutylxanthine