Human adaptation to ischemia by preconditioning or unstable angina: involvement of nuclear factor kappa B, but not hypoxia-inducible factor 1 alpha in the heart.

OBJECTIVE: Ischemic preconditioning reduces infarct size and improves hemodynamic function. Unstable angina may be a clinical analogue to ischemic preconditioning, and involve activation of gene programs. We hypothesized that preceding unstable angina and/or ischemic preconditioning activated genes regulated by nuclear factor kappa B (NFkappaB) or hypoxia-inducible factor 1 alpha in parallel to improved cardiac function. METHODS: Patients undergoing coronary artery bypass grafting with stable or unstable angina were subjected to ischemic preconditioning or sham treatment (n=10-11 in each group). Central hemodynamics were monitored. Left ventricular and atrial biopsies were harvested before cardioplegic arrest and after 25 min of reperfusion. Expression of heat shock protein 72 was evaluated by immunoblot, and activation of NFkappaB was detected by electrophoretic mobility shift assay. Real-time PCR was used to quantify expression of genes regulated by NFkappaB (inducible nitric oxide synthase, tumor necrosis factor-alpha, intercellular adhesion molecule 1) or by hypoxia-inducible factor 1 alpha (heme oxygenase-1, glucose transporter-1 and vascular endothelial growth factor-A). RESULTS: Ischemic preconditioning improved postoperative cardiac index and left ventricular stroke work index in both stable and unstable groups on the first postoperative day. Expression of hypoxia-inducible factor 1 alpha regulated genes was not influenced by cardioplegia and reperfusion, ischemic preconditioning or unstable angina. Expression of the NFkappaB-regulated genes increased after cardioplegia and reperfusion, but this was not influenced by ischemic preconditioning in stable patients. Inducible nitric oxide synthase and tumor necrosis factor expression were reduced after ischemic preconditioning in patients with unstable angina. There were no significant differences in gene expression between stable and unstable patients before cardioplegia and ischemic preconditioning. NFkappaB translocation at reperfusion was reduced in stable preconditioned and unstable control patients compared to stable controls. Heat shock protein 72 expression increased after preconditioning of unstable patients. CONCLUSION: Cardiac function was improved by ischemic preconditioning in both stable and unstable patients. Unstable angina per se had no effect. NFkappaB-regulated genes were influenced by ischemic preconditioning, but hypoxia-inducible genes were not.

CDR3 sequence preference of TCRBV8S2+ T cells within the CNS does not reflect single amino acid dependent avidity expansion.

To investigate the influence of antigen and restricting MHC class II molecule on the T cell repertoire, we varied the peptide source by immunizing either with myelin basic protein (MBP) (rat)63-88 or MBP(GUINEA PIG (GP))63-88, which differ in the core region of the peptide binding site at position 79 by a single exchange of threonine (T) to serine (S) and by altering the MHC by immunizing MHC congenic LEW (RT1(1)) and LEW.1W (RT1u) rats. In both MHC haplotypes both peptides lead to oligoclonal dominance of TCRBV8S2 expressing T cells within the central nervous system (CNS) as assessed by complementary determining region 3 (CDR3) spectratyping. In contrast cytofluorometric analysis indicated that only MBP(GP)63-88 in context with the RT1(l) haplotype of the LEW rat lead to strong expansions of TCRBV8S2 expressing T cells within the CNS. Importantly, the small conservative change from S to T at position 79 within MBP63-88 had a strong influence both on the encephalitogenic potential of the peptide and on the number of TCRBV8S2+ T cells infiltrating the CNS. These results demonstrate that even minor changes in only one side chain of an amino acid within an (auto)antigen can dramatically alter TCR avidity for certain MHC class II/peptide complexes.

CD1d-dependent activation of NKT cells aggravates atherosclerosis.

Adaptive and innate immunity have been implicated in the pathogenesis of atherosclerosis. Given their abundance in the lesion, lipids might be targets of the atherosclerosis-associated immune response. Natural killer T (NKT) cells can recognize lipid antigens presented by CD1 molecules. We have explored the role of CD1d-restricted NKT cells in atherosclerosis by using apolipoprotein E-deficient (apoE-/-) mice, a hypercholesterolemic mouse model that develops atherosclerosis. ApoE-/- mice crossed with CD1d-/- (CD1d-/-apoE-/-) mice exhibited a 25% decrease in lesion size compared with apoE-/- mice. Administration of alpha-galactosylceramide, a synthetic glycolipid that activates NKT cells via CD1d, induced a 50% increase in lesion size in apoE-/- mice, whereas it did not affect lesion size in apoE-/-CD1d-/- mice. Treatment was accompanied by an early burst of cytokines (IFNgamma, MCP-1, TNFalpha, IL-2, IL-4, IL-5, and IL-6) followed by sustained increases in IFNgamma and IL-4 transcripts in the spleen and aorta. Early activation of both T and B cells was followed by recruitment of T and NKT cells to the aorta and activation of inflammatory genes. These results show that activation of CD1d-restricted NKT cells exacerbates atherosclerosis.