title: Lipopolysaccharide and cytokines inhibit rat cardiomyocyte contractility in vitro.
abstract: BACKGROUND
  Sepsis-induced cardiomyopathy (SIC) is thought to be the result of detrimental effects of inflammatory mediators on the cardiac muscle. Here we studied the effects of prolonged (24 ± 4 h) exposure of adult rat ventricular myocytes (ARVM) to bacterial lipopolysaccharide (LPS) and inflammatory cytokines tumor necrosis factor (TNF) and interleukins-1 (IL-1) and IL-6.
  
  
  METHODS
  We measured sarcomere shortening (SS) and cellular calcium (Ca(2+)) transients (ΔCai, with fura-2 AM) in isolated cardiomyocytes externally paced at 5 Hz at 37°C.
  
  
  RESULTS
  SS decreased after incubation with LPS (100 μg/mL), IL-1 (100 ng/mL), and IL-6 (30 ng/mL), but not with lesser doses of these mediators, or TNF (10-100 ng/mL). A combination of LPS (100 μg/mL), TNF, IL-1, and IL-6 (each 100 ng/mL; i.e., "Cytomix-100") induced a maximal decrease in SS and ΔCai. Sarcoplasmic reticulum (SR) Ca(2+) load (CaSR, measured with caffeine) was unchanged by Cytomix-100; however, SR fractional release (ΔCai/CaSR) was decreased. Underlying these effects, Ca(2+) influx into the cell (via L-type Ca(2+) channels, LTCC) and Ca(2+) extrusion via Na(+)/Ca(2+) exchange were decreased by Cytomix-100. SR Ca(2+) pump (SERCA) (SR Ca(2+) ATPase) was not affected.
  
  
  CONCLUSIONS
  Prolonged exposure of ARVM to a mixture of LPS and inflammatory cytokines inhibits cell contractility. The effect is mediated by the inhibition of Ca(2+) influx via LTCC, and partially opposed by the inhibition of Na(+)/Ca(2+) exchange. Because both mechanisms are commonly seen in animal models of SIC, we conclude that prolonged challenge with Cytomix-100 of ARVM may represent an accurate in vitro model for SIC.
authors.affiliation: Cardiovascular Medicine Section, Department of Medicine, Boston University Medical Center, Boston, Massachusetts; Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts. Electronic address: ihobai@partners.org.
authors.forename: Ion A
authors.initials: IA
authors.lastname: Hobai
authors.affiliation: Cardiovascular Medicine Section, Department of Medicine, Boston University Medical Center, Boston, Massachusetts.
authors.forename: Justin C
authors.initials: JC
authors.lastname: Morse
authors.affiliation: Cardiovascular Medicine Section, Department of Medicine, Boston University Medical Center, Boston, Massachusetts.
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Siwik
authors.affiliation: Cardiovascular Medicine Section, Department of Medicine, Boston University Medical Center, Boston, Massachusetts.
authors.forename: Wilson S
authors.initials: WS
authors.lastname: Colucci
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D009202:Cardiomyopathies / Q000209:etiology*; D002478:Cells, Cultured; D016207:Cytokines / Q000633:toxicity*; D008070:Lipopolysaccharides / Q000633:toxicity*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000201:enzymology; D017207:Rats, Sprague-Dawley; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D018805:Sepsis / Q000150:complications*
chemical_list: D020746:Calcium Channels, L-Type; D016207:Cytokines; D008070:Lipopolysaccharides; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium
keywords: Calcium; Excitation–contraction coupling; L-type calcium channel; Na(+)/Ca(2+) exchange; SERCA; Sepsis; Sepsis-induced cardiomyopathy