title: Morphine potentiates LPS-induced autophagy initiation but inhibits autophagosomal maturation through distinct TLR4-dependent and independent pathways.
abstract: OBJECTIVE
  Opioids are the most prescribed analgesics for moderate and severe pain management; however, chronic use impairs host innate immune response and increases susceptibility to infection. Recently, autophagy has been shown to be an innate defence mechanism against bacterial infection. The effect of autophagy-induced bacterial clearance following morphine treatment has not been previously investigated.
  
  
  METHODS
  Autophagosomes were visualized by confocal microscopy following GFP-LC3 transfection and also by transmission electron microscopy. The relative protein levels were analysed by Western blot. Macrophages were transfected with GFP-mcherry-LC3 simultaneously to monitor autolysosome formation and subsequent events that lead to degradation.
  
  
  RESULTS
  Morphine treatment potentiated LPS-induced vesicular translocation of GFP-LC3 with a concurrent increase in LC3-II levels. In addition, morphine upregulated LPS-induced Beclin1 level, but downregulated Bcl-2 level. We further show that p38 MAP kinase signalling is required for autophagy activation. In contrast, morphine inhibited LPS-induced autophagosome maturation and autophagolysosomal fusion as indicated by the failure to recruit LAMP1 into autophagosome and reduced degradation of SQSTM1/p62 protein level. Morphine modulation of LPS-induced autophagosome maturation visualized using co-localization of GFP-mcherry-LC3 was TLR4 independent, but mediated through μ opioid receptor signalling. Correspondingly, morphine and LPS co-treatment significantly increased Streptococcus pneumoniae load, when compared with LPS treatment alone.
  
  
  CONCLUSIONS
  These observations imply that although morphine treatment facilitates LPS-induced autophagy, it inhibits autophagolysosomal fusion leading to decreased bacterial clearance and increased bacterial load. These observations support the increased susceptibility to infection and the prevalence of persistent infection in the drug abuse population.
authors: Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors: Jing
authors: J
authors: Wan
authors: Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors: Jing
authors: J
authors: Ma
authors: Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors: Vidhu
authors: V
authors: Anand
authors: Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455.
authors: Sundaram
authors: S
authors: Ramakrishnan
authors: Department of Surgery, University of Minnesota, Minneapolis, MN 55455.|Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455.
authors: Sabita
authors: S
authors: Roy
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects*; D002460:Cell Line; D007113:Immunity, Innate / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D008070:Lipopolysaccharides; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D009020:Morphine
keywords: LPS; TLR4; autophagosome; macrophage; maturation; morphine