Critical Care Medicine  |   January 2017
Transient Receptor Potential Melastatin 2 Regulates Phagosome Maturation and Is Required for Bacterial Clearance in Escherichia coli Sepsis
Author Notes
  • From the Department of Anesthesiology and Intensive Care Unit, The First Affiliated Hospital (Z.Z., P.C., K.Z., X.F.) and Clinical Research Center, The Children’s Hospital (Q.C.), School of Medicine, Zhejiang University, Hangzhou, China.
  • Submitted for publication February 25, 2016. Accepted for publication September 23, 2016.
    Submitted for publication February 25, 2016. Accepted for publication September 23, 2016.×
  • Q.C. and X.F. contributed equally to this article.
    Q.C. and X.F. contributed equally to this article.×
  • Address correspondence to Dr. Fang: Department of Anesthesiology, the First Affiliated Hospital, School of Medicine, Zhejiang University, QingChun Road 79, 310003 Hangzhou, China. xiangming_fang@163.com. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Critical Care Medicine / Basic Science / Critical Care / Infectious Disease
Critical Care Medicine   |   January 2017
Transient Receptor Potential Melastatin 2 Regulates Phagosome Maturation and Is Required for Bacterial Clearance in Escherichia coli Sepsis
Anesthesiology 1 2017, Vol.126, 128-139. doi:10.1097/ALN.0000000000001430
Anesthesiology 1 2017, Vol.126, 128-139. doi:10.1097/ALN.0000000000001430
Abstract

Background: Transient receptor potential melastatin 2 is a Ca2+-permeable cation channel abundantly expressed in macrophages. Trpm2−/− mice showed exacerbated infection and mortality during polymicrobial sepsis, which is associated with inefficient bacterial killing in macrophages. However, the mechanism of transient receptor potential melastatin 2 regulating bacterial killing remains unknown.

Methods: Trpm2−/− mice were intraperitoneally injected with Escherichia coli. The survival rate (n = 21) and bacterial burden (n = 5) were assessed. The processes of phagosome maturation and phagosome–lysosome fusion in peritoneal macrophages were extensively studied. The impact of increasing intracellular Ca2+ concentration on bacterial clearance in macrophages (n = 3) and on survival rate of Trpm2−/− mice infected with E. coli (n = 21) was investigated.

Results: Trpm2−/− mice exhibited increased mortality (85% vs. 54%; P < 0.01) and aggravated bacterial burden during E. coli sepsis. Trpm2−/− peritoneal macrophages infected with E. coli showed dampened recruitment of lysosomal-associated membrane protein 1 and impaired phagosome maturation evidenced by a decrease in the accumulation of early endosome antigen 1, whereas a normal acquisition of Ras-related protein in brain 5. Increasing the cytosolic Ca2+ concentration in Trpm2−/− peritoneal macrophages via ionomycin treatment facilitated early endosome antigen 1 recruitment to Ras-related protein in brain 5 and phagosomal localization of lysosomal-associated membrane protein 1 and consequently enhanced bactericidal activity. Adoptive transfer of ionomycin-treated Trpm2−/− peritoneal macrophages improved bacterial clearance and survival (67% vs. 29%; P < 0.01) in Trpm2−/− mice challenged with E. coli.

Conclusions: Transient receptor potential melastatin 2 plays a critical role in host defense against invading bacteria via promoting phagosome maturation through facilitation of early endosome antigen 1 recruitment.