Cyclo(His-Pro) inhibits NLRP3 inflammasome cascade in ALS microglial cells

Mol Cell Neurosci. 2019 Jan:94:23-31. doi: 10.1016/j.mcn.2018.11.002. Epub 2018 Nov 13.

Abstract

Neuroinflammation, i.e. self-propelling progressive cycle of microglial activation and neuron damage, as well as improper protein folding, are recognized as major culprits of neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS). Mutations in several proteins have been linked to ALS pathogenesis, including the G93A mutation in the superoxide dismutase 1 (SOD1) enzyme. SOD1(G93A) mutant is prone to aggregate thus inducing both oxidative stress and neuroinflammation. In this study we used hSOD1(G93A) microglial cells to investigate the effects of the antioxidant and anti-inflammatory cyclic dipeptide (His-Pro) on LPS-induced inflammasome activation. We found that cyclo(His-Pro) inhibits NLRP3 inflammasome activation by reducing protein nitration via reduction in NO and ROS levels, indicative of lower peroxynitrite generation by LPS. Low levels in peroxynitrite are related to NF-κB inhibition responsible for iNOS down-regulation and NO dampening. On the other hand, cyclo(His-Pro)-mediated ROS attenuation, not linked to Nrf2 activation in this cellular model, is ascribed to increased soluble SOD1 activity due to the up-regulation of Hsp70 and Hsp27 expression. Conclusively, our results, besides corroborating the anti-inflammatory properties of cyclo(His-Pro), highlight a novel role of the cyclic dipeptide as a proteostasis regulator, and therefore a good candidate for the treatment of ALS and other misfolding diseases.

Keywords: Caspase 1; Diketopiperazine; NLRP3; NOX2; Peroxynitrite; SOD1 activity; iNOS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyotrophic Lateral Sclerosis / drug therapy*
  • Amyotrophic Lateral Sclerosis / metabolism
  • Animals
  • Anti-Inflammatory Agents / pharmacology*
  • Disease Models, Animal
  • Inflammasomes / drug effects*
  • Inflammasomes / metabolism
  • Mice
  • Mice, Transgenic
  • Microglia / drug effects*
  • Microglia / metabolism
  • Motor Neurons / drug effects
  • NLR Family, Pyrin Domain-Containing 3 Protein / drug effects*
  • NLR Family, Pyrin Domain-Containing 3 Protein / genetics
  • NLR Family, Pyrin Domain-Containing 3 Protein / metabolism
  • Oxidative Stress / drug effects
  • Superoxide Dismutase / pharmacology

Substances

  • Anti-Inflammatory Agents
  • Inflammasomes
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Nlrp3 protein, mouse
  • Superoxide Dismutase