Extracellular BCL2 proteins are danger-associated molecular patterns that reduce tissue damage in murine models of ischemia-reperfusion injury.
BACKGROUND
Ischemia-reperfusion (I/R) injury contributes to organ dysfunction in a variety of clinical disorders, including myocardial infarction, stroke, organ transplantation, and hemorrhagic shock. Recent investigations have demonstrated that apoptosis as an important mechanism of cell death leading to organ dysfunction following I/R. Intracellular danger-associated molecular patterns (DAMPs) released during cell death can activate cytoprotective responses by engaging receptors of the innate immune system.


RESULTS
Ischemia was induced in the mouse hind limb by tourniquet or in the heart by coronary artery ligation. Reperfusion injury of skeletal or cardiac muscle was markedly reduced by intraperitoneal or subcutaneous injection of recombinant human (rh)BCL2 protein or rhBCL2-related protein A1 (BCL2A1) (50 ng/g) given prior to ischemia or at the time of reperfusion. The cytoprotective activity of extracellular rhBCL2 or rhBCL2A1 protein was mapped to the BH4 domain, as treatment with a mutant BCL2 protein lacking the BH4 domain was not protective, whereas peptides derived from the BH4 domain of BCL2 or the BH4-like domain of BCL2A1 were. Protection by extracellular rhBCL2 or rhBCL2A1 was associated with a reduction in apoptosis in skeletal and cardiac muscle following I/R, concomitant with increased expression of endogenous mouse BCL2 (mBCL2) protein. Notably, treatment with rhBCL2A1 protein did not protect mice deficient in toll-like receptor-2 (TLR2) or the adaptor protein, myeloid differentiation factor-88 (MyD88).


CONCLUSIONS
Treatment with cytokine-like doses of rhBCL2 or rhBCL2A1 protein or BH4-domain peptides reduces apoptosis and tissue injury following I/R by a TLR2-MyD88-dependent mechanism. These findings establish a novel extracellular cytoprotective activity of BCL2 BH4-domain proteins as potent cytoprotective DAMPs.
Iwata
Akiko
A
Department of Surgery, University of Washington, Seattle, Washington, United States of America.
Morgan-Stevenson
Vicki
V
Schwartz
Barbara
B
Liu
Li
L
Tupper
Joan
J
Zhu
Xiaodong
X
Harlan
John
J
Winn
Robert
R
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D004195:Disease Models, Animal; D006614:Hindlimb / Q000098:blood supply; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015778:Minor Histocompatibility Antigens; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000098:blood supply / Q000187:drug effects; D053594:Myeloid Differentiation Factor 88 / Q000172:deficiency / Q000235:genetics; D017202:Myocardial Ischemia / Q000473:pathology / Q000517:prevention & control; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology; D015427:Reperfusion Injury / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D015398:Signal Transduction; D051195:Toll-Like Receptor 2 / Q000172:deficiency / Q000235:genetics; D014111:Tourniquets / Q000009:adverse effects
C096816:BCL2-related protein A1; D015778:Minor Histocompatibility Antigens; D053594:Myeloid Differentiation Factor 88; D010455:Peptides; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D051195:Toll-Like Receptor 2; C052617:Bcl2 protein, mouse