Blood Journal
Leading the way in experimental and clinical research in hematology

Heme induces programmed necrosis on macrophages through autocrine TNF and ROS production

  1. Guilherme B. Fortes1,
  2. Leticia S. Alves1,
  3. Rosane de Oliveira1,2,
  4. Fabianno F. Dutra1,
  5. Danielle Rodrigues1,
  6. Patricia L. Fernandez3,
  7. Thais Souto-Padron1,
  8. María José De Rosa2,
  9. Michelle Kelliher2,
  10. Douglas Golenbock2,
  11. Francis K. M. Chan2, and
  12. Marcelo T. Bozza1
  1. 1Instituto de Microbiologia Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil;
  2. 2University of Massachusetts Medical School, Worcester, MA;
  3. 3Instituto de Investigaciones Científicas y Servicios de Alta Tecnologia, Ciudad de Panamá, Panamá

Abstract

Diseases that cause hemolysis or myonecrosis lead to the leakage of large amounts of heme proteins. Free heme has proinflammatory and cytotoxic effects. Heme induces TLR4-dependent production of tumor necrosis factor (TNF), whereas heme cytotoxicity has been attributed to its ability to intercalate into cell membranes and cause oxidative stress. We show that heme caused early macrophage death characterized by the loss of plasma membrane integrity and morphologic features resembling necrosis. Heme-induced cell death required TNFR1 and TLR4/MyD88-dependent TNF production. Addition of TNF to Tlr4−/− or to Myd88−/− macrophages restored heme-induced cell death. The use of necrostatin-1, a selective inhibitor of receptor-interacting protein 1 (RIP1, also known as RIPK1), or cells deficient in Rip1 or Rip3 revealed a critical role for RIP proteins in heme-induced cell death. Serum, antioxidants, iron chelation, or inhibition of c-Jun N-terminal kinase (JNK) ameliorated heme-induced oxidative burst and blocked macrophage cell death. Macrophages from heme oxygenase-1 deficient mice (Hmox1−/−) had increased oxidative stress and were more sensitive to heme. Taken together, these results revealed that heme induces macrophage necrosis through 2 synergistic mechanisms: TLR4/Myd88-dependent expression of TNF and TLR4-independent generation of ROS.

  • Submitted August 21, 2011.
  • Accepted January 1, 2012.
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