Involvement of cathepsin B in the processing and secretion of interleukin-1beta in chromogranin A-stimulated microglia

Glia. 2010 Jan 1;58(1):114-24. doi: 10.1002/glia.20906.

Abstract

Cathepsin B (CB) is a cysteine lysosomal protease implicated in a number of inflammatory diseases. Although it is now evident that caspase-1, an essential enzyme for maturation of interleukin-1beta (IL-1beta), can be activated through the inflammasome, there is still evidence suggesting the existence of lysosomal-proinflammatory caspase pathways. In the present study, a marked induction of pro-IL-1beta, its processing to the mature form and secretion were observed in the primary cultured microglia prepared from wild-type mice after stimulation with chromogranin A (CGA). Although pro-IL-1beta also markedly increased in microglia prepared from CB-deficient mice, CB-deficiency abrogated the pro-IL-1beta processing. CA-074Me, a specific inhibitor for CB, inhibited the pro-IL-1beta maturation and its release from microglia. Furthermore, the caspase-1 activation was also inhibited by CA-074Me and E-64d, a broad cysteine protease inhibitor. After treatment with CGA, CB was markedly induced at both protein and mRNA levels. The induced pro-CB was rapidly processed to its mature form. The immunoreactivity for CB co-localized with both that for caspase-1 and the cleaved IL-1beta, in the acidic enlarged lysosomes. Inconsistent with these in vitro observations, the immunoreactivity for the cleaved IL-1beta was markedly observed in microglia of the hippocampus from aged wild-type but not CB-deficient mice. These observations strongly suggest that CB plays a key role in the pro-IL-1beta maturation through the caspase-1 activation in enlarged lysosomes of CGA-treated microglia. Therefore, either pharmacological or genetic inhibition of CB may provide therapeutic intervention in inflammation-associated neurological diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Animals
  • Animals, Newborn
  • Caspase 1 / metabolism
  • Cathepsin B / deficiency
  • Cathepsin B / physiology*
  • Cell Survival / drug effects
  • Cells, Cultured
  • Cerebral Cortex / cytology
  • Chromogranin A / pharmacology*
  • Drug Interactions
  • Enzyme Inhibitors / pharmacology
  • Enzyme-Linked Immunosorbent Assay / methods
  • Gene Expression Regulation / drug effects
  • Hippocampus / drug effects
  • Hippocampus / metabolism
  • Interleukin-1beta / genetics
  • Interleukin-1beta / metabolism*
  • Lysosome-Associated Membrane Glycoproteins / metabolism
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Microglia / drug effects*
  • Microglia / metabolism
  • Nitrites / metabolism
  • Pepstatins / pharmacology
  • RNA, Messenger / metabolism
  • Time Factors
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Chromogranin A
  • Enzyme Inhibitors
  • Interleukin-1beta
  • Lysosome-Associated Membrane Glycoproteins
  • Nitrites
  • Pepstatins
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha
  • Cathepsin B
  • Caspase 1
  • pepstatin