TNNI3K is a new cardiac-specific MAP kinase whose gene is localized to 1p31.1 and that belongs to a tyrosine kinase-like branch in the kinase tree of the human genome. In the present study we investigated the role of TNNI3K in the cardiac myogenesis process and in the repair of ischemic injury. Pluripotent P19CL6 cells with or without transfection by pcDNA6-TNNI3K plasmid were used to induce differentiation into beating cardiomyocytes. TNNI3K promoted the differentiation process, judging from the increasing beating mass and increased number of alpha-actinin-positive cells. TNNI3K improved cardiac function by enhancing beating frequency and increasing the contractile force and epinephrine response of spontaneous action potentials without an increase of the single-cell size. TNNI3K suppressed phosphorylation of cardiac troponin I, annexin-V(+) cells, Bax protein, and p38/JNK-mediated apoptosis. Intramyocardial administration of TNNI3K-overexpressing P19CL6 cells in mice with myocardial infarction improved cardiac performance and attenuated ventricular remodeling compared with injection of wild-type P19CL6 cells. In conclusion, our study clearly indicates that TNNI3K promotes cardiomyogenesis, enhances cardiac performance, and protects the myocardium from ischemic injury by suppressing p38/JNK-mediated apoptosis. Therefore, modulation of TNNI3K activity would be a useful therapeutic approach for ischemic cardiac disease.

No abstract

ABSTRACT:The presentation of antigenic peptides by major histocompatibility complex (MHC) class II to CD4 ϩ T cells is crucial to initiate immune responses. We developed a new system for delivery of an antigenic peptide to the MHC class II pathway, using the invariant chain (Ii). We designed a mutated human p33-form Ii, CLIP-substituted Ii, in which streptococcal M12p55-68 (RDLEQAYNELSGEA) was substituted for CLIP (class II associated invariant chain peptide) . We examined the peptide presenting function of this construct, in comparison with the previously reported C-terminal fused Ii, in which a cathepsin cleavage site and M12p54-68 was ligated to the C-terminus of Ii. Mouse L cell transfectants expressing either of these two mutated Ii along with HLA-DR4 could process and present M12p55-68 to the peptide specific and DR4-restricted CD4 ϩ T cell clone. CLIP-substituted Ii was much more efficient in antigen presentation than was the C-terminal fused Ii. Similar to the wild-type Ii, the CLIP-substituted Ii was associated intracellularly with DR4 molecules. These results indicate that the peptide substituted for CLIP of Ii p33 bound to the groove of DR molecules in the same manner as CLIP and it was preferentially presented to the CD4 ϩ T cell clone in the absence of HLA-DM molecules. This system may prove useful for immunotherapy with DNA vaccines or for construction of an antigen presenting cell library with diverse peptides.

Abstract. We investigated effects of sasanquasaponin (SQS), a traditional Chinese herb's effective component, on ischemia and reperfusion injury in mouse hearts and the possible role of intracellular Cl -homeostasis on SQS's protective effects during ischemia and reperfusion. An in vivo experimental ischemia model was made in mice (weight 27 -45 g) using ligation of left anterior descending coronary artery, and in vitro models were made in perfused hearts by stopping flow or in isolated ventricular myocytes by hypoxia. The in vivo results showed that SQS inhibited cardiac arrhythmias during ischemia and reperfusion. Incidence of arrhythmias during ischemia and reperfusion, including ventricular premature beats and ventricular fibrillation, was significantly decreased in the SQS-pretreated group (P<0.05). Results in perfused hearts showed that SQS suppressed the arrhythmias, prevented against ischemia-induced decrease in contract force and promoted the force recovery from reperfusion. ] i during ischemia and reperfusion (P<0.05). Our results showed that SQS protected against ischemia / reperfusion-induced cardiac injury in mouse hearts and that modulation of intracellular Cl -homeostasis by SQS would play a role in its anti-arrhythmia effects during ischemia and reperfusion.

We investigated changes in voltage-gated Na+ currents and effects of extracellular Na+ on proliferation in HLA-DR-restricted human CD4+ αβ T cells after stimulation with a non-self antigenic peptide, M12p54–68. In the absence of antigenic peptide, neither single (n = 80) nor APC-contacted (n = 71) T cells showed voltage-gated inward currents recording with whole-cell patch-clamp techniques, even with Ca2+ and Na+ ions present in the perfusion solution. However, with the same recording conditions, 31% (26 of 84) of APC-contacted T cells stimulated with the antigenic peptide showed voltage-dependent inward currents that were elicited from −60 mV. The inward currents were not inhibited in extracellular Ca2+-free conditions or in the presence of 1 mM NiCl2. However, they were completely inhibited in extracellular Na+-free conditions, which were made by replacing Na+ with iso-osmotic N-methyl-d-glucamine or choline. The Na+ currents were insensitive to tetrodotoxin, a classical blocker of Na+ channels, but were dose-dependently inhibited by amiloride, a potassium-sparing pyrazine diuretic. Furthermore, the Ag-specific proliferative response of T cells was completely inhibited in Na+-free Tyrode’s solution and was suppressed by amiloride in a dose-dependent manner. Our findings suggest that activation of amiloride-sensitive and voltage-gated Na+ channels would be an important step to allow an adequate influx of Na+ and maintain a sustained high Ca2+ level during T cell activation.