Thyroid hormone (TH) is critical for tissue differentiation at early stages of development, induces physiological hypertrophy and regulates the expression of important contractile proteins such as myosin heavy chain (MHC) isoform and calcium cycling proteins. Furthermore, TH seems to control the response to stress by regulating important cardioprotective molecules such as heat shock proteins (HSPs). Thus, the present study investigated whether TH administration immediately after acute myocardial infarction can favourably remodel the post-infarcted myocardium. Acute myocardial infarction was induced in rats by coronary artery ligation (AMI, n=10), while SHAM-operated animals served as controls (SHAM, n = 8). TH was administered for 13 weeks (AMI-THYR, n = 9). Cardiac contractile function and left ventricular (LV) chamber remodelling was assessed by serial echocardiography and in Langendorff heart preparations. AMI significantly reduced LV ejection fraction (EF%); 30.0 (s.e.m, 2.3) Vs. 73.8 (1.8) in SHAM, P < 0.05. In addition, +dp/dt and -dp/dt (in mmHg/s) were 4,051 (343) and 2,333 (118) respectively for SHAM Vs. 2,102 (290) and 1,368 (181) for AMI, P < 0.05. With TH treatment, EF% was increased to 49.5 (2.7) in AMI-THYR, P < 0.05, while +dp/dt and -dp/dt (in mmHg/s) were 3,708 (231) and 2,035 (95) for AMI-THYR, P < 0.05 Vs. AMI. A marked elevation of the expression of beta-MHC and a reduced ratio of SERCA/Phospholamban were found in viable myocardium of AMI hearts, which was prevented by TH. Furthermore, heat shock protein 70 myocardial content was decreased in AMI hearts and was significantly increased after TH treatment. An ellipsoidal reshaping of LV chamber was observed with TH; cardiac sphericity index, (ratio of long/short axis, SI), was 1.98 (0.03) for SHAM, 1.52 (0.05) for AMI and 1.72(0.02) for AMI-THYR, P < 0.05. In conclusion, long-term TH administration immediately after AMI results in sustained improvement of cardiac haemodynamics.

Although it has long been recognized that thyroid hormone is an effective positive inotrope, its efficacy in supporting hemodynamics in the acute setting of ischaemia and reperfusion (R) without worsening reperfusion injury remains largely unknown. Thus, we investigated the effects of triiodothyronine (T3) on reperfusion injury in a Langendorff-perfused rat heart model of 30 min zero-flow ischaemia and 60 min of (R) with or without T3 (40 microg/l) at R, T3-R60, n = 11 and CNT-R60, n = 10, respectively. Furthermore, phosphorylated levels of intracellular kinases were measured at 5, 15 and 60 min of R. T3 markedly improved postischaemic recovery of left ventricular developed pressure (LVDP%); 56.0% (SEM, 4.4) in T3-R60 versus 38.8% (3.1) in CNT-R60, P < 0.05. Furthermore, LDH release was significantly lower in T3-R60. Apoptosis detection by fluorescent probe optical imaging showed increased fluorescent signal in CNT-R60 hearts, while the signal was hardly detectable in T3-R60 hearts. Similarly, caspase-3 activity was found to be 78.2 (8.2) in CNT-R60 vs 40.5 (7.1) in T3-R60 hearts, P < 0.05. This response was associated with significantly lower levels of phospho-p38 MAPK at any time point of R. No significant changes in phospho- ERK1/2 and JNK levels were observed between groups. Phospho-Akt levels were significantly lower in T3 treated group at 5 min and no change in phospho-Akt levels were observed at 15 and 60 min between groups. In conclusion, T3 administration at reperfusion can improve postischaemic recovery of function while limiting apoptosis. This may constitute a paradigm of a positive inotropic agent with anti-apoptotic action suitable for supporting hemodynamics in the clinical setting of ischaemia-reperfusion.

Heart failure (HF) is a physiological state in which cardiac output is insufficient to meet the needs of the body. It is a clinical syndrome characterized by impaired ability of the left ventricle to either fill or eject blood efficiently. HF is a disease of multiple aetiologies leading to progressive cardiac dysfunction and it is the leading cause of deaths in both developed and developing countries. HF is responsible for about 73,000 deaths in the UK each year. In the USA, HF affects 5.8 million people and 550,000 new cases are diagnosed annually. Cardiac remodelling (CD), which plays an important role in pathogenesis of HF, is viewed as stress response to an index event such as myocardial ischaemia or imposition of mechanical load leading to a series of structural and functional changes in the viable myocardium. Protein kinase C (PKC) isozymes are a family of serine/threonine kinases. PKC is a central enzyme in the regulation of growth, hypertrophy, and mediators of signal transduction pathways. In response to circulating hormones, activation of PKC triggers a multitude of intracellular events influencing multiple physiological processes in the heart, including heart rate, contraction, and relaxation. Recent research implicates PKC activation in the pathophysiology of a number of cardiovascular disease states. Few reports are available that examine PKC in normal and diseased human hearts. This review describes the structure, functions, and distribution of PKCs in the healthy and diseased heart with emphasis on the human heart and, also importantly, their regulation in heart failure.

We have previously shown that long-term thyroxine administration can protect the heart against ischemia. In the present study, we investigated whether thyroxine-induced cardioprotection can mimic the pattern of protection that is afforded by a well-established cardioprotective means such as ischemic preconditioning. In a Langendorff-perfused rat heart preparation, after an initial stabilization, normal and thyroxine-treated hearts were subjected to 20 minutes of zero-flow global ischemia followed by 45 minutes of reperfusion. In thyroxine-treated hearts, phospho-p38 mitogen-activated protein kinase (MAPK) was found to be less at the end of the ischemic period, whereas ischemic contracture was accelerated and postischemic recovery was increased in comparison to normal hearts. In addition, normal hearts were subjected to a four-cycle preconditioning protocol before ischemia. Phospho-p38 MAPK was found to be less at the end of the ischemic period in preconditioned hearts, whereas ischemic contracture was accelerated and postischemic functional recovery was increased in those hearts in comparison to nonpreconditioned hearts. An increase in basal expression and phosphorylation of PKCdelta was also found to occur after long-term thyroxine administration. We conclude that long-term thyroxine administration can protect the heart from ischemic injury through a pattern of protection that closely resembles that of ischemic preconditioning.

Thyroid hormone administration early after infarction attenuates cardiac remodeling and significantly improves myocardial performance.

Objective: This study investigated whether changes in thyroid hormone (TH) in plasma are associated with the recovery of cardiac function in patients with acute myocardial infarction (AMI). Previous experimental studies have provided evidence of potential implication of TH signaling in post-ischemic recovery of cardiac function. Methods: A total of 47 patients with AMI and early reperfusion therapy were included in this study. Myocardial injury was analyzed by peak creatinine kinase-MB (CKMB) and cardiac function was assessed by echocardiographic left ventricular ejection fraction (LVEF%). Recovery of function (DEF%) was estimated as the difference of LVEF% between 48 h and 6 months (6 mo) after AMI. Total triiodothyronine (T 3 ), thyroxine (T 4 ), and TSH were measured in plasma at different time points (24 h, 48 h, 5 d, and 6 mo). Results: A significant correlation between LVEF% and T 3 (rZ0.5, PZ0.0004) was found early after AMI (48 h), whereas no correlation was observed between CKMB and T 3 (rZK0.04, PZ0.81). A strong correlation was found between DEF% and total T 3 (rZ0.64, PZ10 K6) at 6 mo after AMI. Furthermore, multivariate regression analysis revealed that T 3 at 6 mo (rZ0.64, r 2 Z0.41, PZ10 K6) was an independent determinant of DEF%. Conclusion: Changes in T 3 levels in plasma are closely correlated with the early and late recovery of cardiac function after AMI. T 3 levels at 6 mo appear to be an independent predictor of late functional recovery.

The present study investigated the response of the hypothyroid heart to ischaemia-reperfusion. Hypothyroidism was induced in Wistar rats by oral administration of propylthiouracil (0·05%) for 3 weeks (HYPO rats), while normal animals (NORM) served as controls. Isolated hearts from NORM and HYPO animals were perfused in Langendorff mode and subjected to zero-flow global ischaemia followed by reperfusion (I/R). Post-ischaemic recovery of left ventricular developed pressure was expressed as % of the initial value (LVDP%). Basal expression of protein kinase C (PKC ) and PKC and phosphorylation of p46 and p54 c-jun NH 2 -terminal kinases (JNKs) in response to I/R were assessed by Western blotting. LVDP% was found to be significantly higher in HYPO hearts than in NORM. At baseline, PKC expression was 1·4-fold more in HYPO than in NORM hearts, P,0·05, while PKC was not changed. Furthermore, basal phospho-p54 and -p46 JNK levels were 2·2-and 2·6-fold more in HYPO than in NORM hearts, P,0·05. In response to I/R, in NORM hearts, phospho-p54 and -p46 JNK levels were 5·5-and 6·0-fold more as compared with the baseline values, P,0·05, while they were not significantly altered in HYPO hearts. HYPO hearts seem to display a phenotype of cardioprotection against ischaemia-reperfusion and this is associated with basal PKC overexpression and attenuated JNK activation after I/R.

This study was undertaken in order to investigate: a) the short-and long-term in vivo effects of cadmium (Cd) on brain acetylcholinesterase (AChE), (Na Brain total antioxidant status was decreased by Cd (30%, PϽ0.01), while it was increased by L-cysteine or L-cysteineπCd (50%, PϽ0.001) in the short-term in vivo treatment. L-cysteine reversed the enzymatic activity changes observed with Cd alone in the high-dose short-term in vivo treatment of rats, as well as the brain AChE inhibition induced by Cd in the in vitro experiments. These results indicate that: a) Cd can influence in a different way the examined enzyme activities after short-and long-term administration, b) Cd may modulate brain cholinergic mechanism(s), neural excitability and metabolic energy production, and c) L-cysteine can have a protective antioxidant effect on the oxidative stress of the brain induced by Cd.