Hsp60 and heme oxygenase-1 (Hsp32) in acute myocardial infarction

Molecular cloning, characterization and expression patterns of HSP60 in the grass carp (Ctenopharyngodon idella)

HSP60 is a highly immunogenic molecule, which is able to activate a large number of T cell types and is implicated in a variety of autoimmune diseases. The grass carp (Ctenopharyngodon idella), a freshwater fish species of the family Cyprinidae, accounts for the third biggest value (USD 4.8 billion) at single species level of major cultured fish species in the world. Here, we isolated and characterized the HSP60 cDNA from grass carp (designated as CiHSP60). Its cDNA was 2434 bp in length and encoded a putative protein of 575 amino acids. BLAST analysis revealed that the CiHSP60 gene shared a high similarity with other known HSP60 sequences. CiHSP60 contained all three classical HSP60 family signatures. The mRNA of CiHSP60 was constitutively expressed in all tested tissues of untreated grass carp, including brain, muscle, trunk kidney, liver, head kidney, skin, spleen, heart, gill, intestine, and fin, with the highest expression level in the blood. CiHSP60 transcript was present in unfertilized eggs, which suggests that CiHSP60 transcription is maternally inherited. Fluorescent real-time quantitative RT-PCR was used to examine the expression of the CiHSP60 gene in grass carp after the challenge with the bacterium Aeromonas hydrophila. A clear time-dependent expression pattern of CiHSP60 was found after the bacterial challenge, and the mRNA expression reached a maximum level at three days post challenge, and returned to control levels after seven days. The upregulated mRNA expression of CiHSP60 in grass carp after bacterial challenge indicates that the HSP60 gene is inducible and involved in immune responses. These results suggest that CiHSP60 plays an important role in A. hydrophila-related diseases and in early embryonic development stages in grass carp.

Myocardial ischemia activates an injurious innate immune signaling via cardiac heat shock protein 60 and Toll-like receptor 4

Innate immune response after transient ischemia is the most common cause of myocardial inflammation and may contribute to injury, yet the detailed signaling mechanisms leading to such a response are not well understood. Herein we tested the hypothesis that myocardial ischemia activates interleukin receptor-associated kinase-1 (IRAK-1), a kinase critical for the innate immune signaling such as that of Toll-like receptors (TLRs), via a mechanism that involves heat shock proteins (HSPs) and TLRs. Coronary artery occlusion induced a rapid myocardial IRAK-1 activation within 30 min in wild-type (WT), TLR2(-/-), or Trif(-/-) mice, but not in TLR4(def) or MyD88(-/-) mice. HSP60 protein was markedly increased in serum or in perfusate of isolated heart following ischemia/reperfusion (I/R). In vitro, recombinant HSP60 induced IRAK-1 activation in cells derived from WT, TLR2(-/-), or Trif(-/-) mice, but not from TLR4(def) or MyD88(-/-) mice. Both myocardial ischemia- and HSP60-induced IRAK-1 activation was abolished by anti-HSP60 antibody. Moreover, HSP60 treatment of cardiomyocytes (CMs) led to marked activation of caspase-8 and -3, but not -9. Expression of dominant-negative mutant of Fas-associated death domain protein or a caspase-8 inhibitor completely blocked HSP60-induced caspase-8 activation, suggesting that HSP60 likely activates an apoptotic program via the death-receptor pathway. In vivo, I/R-induced myocardial apoptosis and cytokine expression were significantly attenuated in TLR4(def) mice or in WT mice treated with anti-HSP60 antibody compared with WT controls. Taken together, the current study demonstrates that myocardial ischemia activates an innate immune signaling via HSP60 and TLR4, which plays an important role in mediating apoptosis and inflammation during I/R.