Parathyroid hormone-related protein (PTHrP) signal cascade modulates myocardial dysfunction in the pressure overloaded heart

Parathyroid hormone-related protein inhibits nitrogen-containing bisphosphonate-induced apoptosis of human periodontal ligament fibroblasts by activating MKP1 phosphatase

Massive production of reactive oxygen species (ROS) in human periodontal ligament fibroblasts (HPdLFs) by nitrogen-containing bisphosphonates (BPs) is the main factor causing BP-related osteonecrosis of the jaw. Further, oxidative stress and apoptosis of fibroblasts induced by ROS are closely associated with the activation of MAPK. Parathyroid hormone-related protein (PTHrP) can block the activity of MAPK by regulating the levels of MAPK phosphatase 1 (MKP1). Therefore, it is speculated that PTHrP can inhibit the apoptosis of HPdLFs caused by nitrogen-containing BP via regulating the expression levels of MKP1. Herein, alendronate sodium salt trihydrate (nitrogen-containing BP, FOS) and HPdLFs were co-cultured for 24 h, 48 h, and 72 h, and the levels of ROS and apoptosis were determined, respectively. After 48 h co-culture, FOS significantly increased the levels of ROS and apoptosis, and high phosphorylation levels of p38, ERK1/2 and p66^Shc were found in this study. However, the inhibitors of p38 and ERK1/2 significantly reduced the apoptosis of HPdLFs. Interestingly, PTHrP pre-treatment significantly reduced the phosphorylation levels of p38, ERK1/2, and p66^Shc. More importantly, MKP1 inhibitor sanguinarine inhibited the dephosphorylation levels of p38, ERK1/2, and p66^Shc caused by PTHrP. Altogether, PTHrP can inhibit nitrogen-containing BP-induced apoptosis of HPdLFs by activating MKP1 phosphatase.

Serum parathyroid hormone levels in patients with chronic right heart failure

Parathyroid hormone (PTH) is a novel cardiovascular biomarker which is particularly useful for detection and assessment of heart failure (HF). However, previous studies examining PTH in heart failure have primarily focused on left HF; thus, the relationship between PTH and right HF remains unclear. The aim of the present study was to evaluate the serum PTH levels in patients with chronic right HF. A total of 154 patients with chronic right HF were enrolled in the present study. A binary logistic regression analysis model was used to assess the independent predictive value of PTH levels in chronic right HF. Partial correlative analysis was used to demonstrate the relevance of PTH levels on the parameters of assessment of right heart function. A multiple linear regression analysis model was used to evaluate the independent factors of PTH levels in patients with right HF. The results showed that the serum PTH levels in the right HF group were significantly higher compared with the control group. After adjusting for predictors of right HF, serum PTH levels were associated with right HF with an odds ratio of 1.066 (95% confidence interval: 1.030-1.102, P<0.001. Serum PTH levels were independently correlated with plasma N-terminal pro-B-type natriuretic peptide levels, right ventricular end-diastolic diameter and severity of lower extremity edema (all P<0.05). Therefore, based on the results of the present study, PTH may be a useful biomarker for detection and assessment of right HF.

Parathyroid Hormone-Related Peptide: A Novel Endocrine Cardioprotective "Conditioning Mimetic"

An as-yet limited body of evidence suggests that calcium-regulating endocrine hormones-in particular, parathyroid hormone-related peptide (PTHrP)-may have unappreciated cardioprotective effects. The current review focuses on the concept that PTHrP may, via modulation of classic cardioprotective signaling pathways, provide a novel strategy to attenuate myocardial ischemia-reperfusion injury.

Serum Parathyroid Hormone Levels Predict Discharge and Readmission for Heart Failure

AIMS

Parathyroid hormone (PTH) levels are useful as a prognostic factor of chronic heart failure (HF) and can predict hospitalization for HF. It is unknown whether serum PTH levels in hospitalized patients with HF can predict discharge and if admission, discharge, or change from admission to discharge PTH measure is the most important predictor of readmission and/or death.

METHODS

A total of 125 consecutive hospitalized patients with HF were enrolled into this study. The receiver operating characteristic (ROC) curves indicated the predicted values of PTH for readmission due to HF and the optimal cutoff points of PTH levels for discharge. The binary logistic regression model indicated an association between PTH levels and readmission due to HF.

RESULTS

The PTH level on admission was positively correlated with the New York Heart Association class and N-terminal pro-B-type natriuretic peptide level. The ROC curves showed that the PTH level at discharge (PTHdis) was of predictive value for readmission within 1 year due to HF. A PTHdis level <45.2 pg/mL was the best cutoff point for discharge, with a sensitivity of 72.1%, specificity of 61.5%, and area under the ROC curve of 0.693 (95% confidence interval [CI] 0.598-0.788). The results of logistic regression analysis showed that PTHdis had an odds ratio of 1.035 for readmission due to HF (95% CI 1.005-1.067).

CONCLUSION

Serum PTH levels in hospitalized patients with HF were shown to be an independent predictor of discharge and PTHdis was the best predictor of readmission and/or death within 1 year due to HF.

Parathyroid hormone-related peptide protects cardiomyocytes from oxidative stress-induced cell death: First evidence of a novel endocrine-cardiovascular interaction

Although there is a growing interest in the molecular cross-talk between the endocrine and cardiovascular systems, the cardiac effects of calcium-regulating hormones (i.e., parathyroid hormone-related peptide (PTHrP)) have not been explored. In this study, we examined the effect of PTHrP on the viability of isolated adult mouse cardiomyocytes subjected to oxidative stress. Myocytes from 19 to 22 week old male 129J/C57BL6 mice were exposed to oxidative insult in the form of H2O2 which led to more than 70% loss of cell viability. Herein we demonstrate, for the first time, that pretreatment with 100 nM PTHrP prior to 100 μM H2O2 incubation prevents H2O2 -induced cell death by more than 50%. Immunoblot analysis revealed H2O2 induction of MKP-1 protein expression while PTHrP decreased MKP-1 expression. Moreover, myocytes derived from MKP1 KO mice were resistant to oxidative injury. No added benefit of PTHrP treatment was noted in MKP-1 null cardiomyocytes. Using specific pharmacological inhibitors we demonstrated that P-p38, P-ERK and P-AKT mediated PTHrP's cardioprotective action. These data provide novel evidence that: i) down-regulation of MKP1 affords profound protection against oxidative stress; and ii) PTHrP is cardioprotective, possibly via down-regulation of MKP-1 and activation of MAPK and PI3K/AKT signaling.

Regulation of sarco(endo)plasmic reticulum Ca2+-ATPase and calsequestrin gene expression in the heart

The precise control of Ca2+levels during the contraction–relaxation cycle in cardiac myocytes is extremely important for normal beat-to-beat contractile activity. The sarcoplasmic reticulum (SR) plays a key role controlling calcium concentration in the cytosol. The SR Ca2+-ATPase (SERCA2) transports Ca2+inside the SR lumen during relaxation of the cardiac myocyte. Calsequestrin (Casq2) is the main protein in the SR lumen, functioning as a Ca2+buffer and participating in Ca2+release by interacting with the ryanodine receptor 2 (RyR2) Ca2+-release channel. Alterations in normal Ca2+handling significantly contribute to the contractile dysfunction observed in cardiac hypertrophy and in heart failure. Transcriptional regulation of the SERCA2 gene has been extensively studied and some of the mechanisms regulating its expression have been elucidated. Overexpression of Sp1 factor in cardiac hypertrophy downregulates SERCA2 gene expression and increased levels of thyroid hormone up-regulates its transcription. Other hormones such norepinephrine, angiotensin II, endothelin-1, parathyroid hormone, prostaglandin-F2α, as well the cytokines tumor necrosis factor-α and interleukin-6 also downregulate SERCA2 expression. Calcium acting through the calcineurin–NFAT (nuclear factor of activated T cells) pathway has been suggested to regulate SERCA2 and CASQ2 gene expression. This review focuses on the current knowledge regarding transcriptional regulation of SERCA2 and CASQ2 genes in the normal and pathologic heart.

Functional proteomic analysis reveals sex-dependent differences in structural and energy-producing myocardial proteins in rat model of alcoholic cardiomyopathy

Long-term ethanol exposure leads to a sexually dimorphic response in both the susceptibility to cardiac pathology (protective effect of the female heart) and the expression of selected myocardial proteins. The purpose of the present study was to use proteomics to examine the effect of chronic alcohol consumption on a broader array of cardiac proteins and how these were affected between the sexes. Male and female rats were maintained for 18 wk on a 40% ethanol-containing diet in which alcohol was provided in drinking water and agar blocks. Differences in the content of specific cardiac proteins in isopycnic centrifugal fractions were determined using mass spectrometry on iTRAQ-labeled tryptic fragments. A random effects model of meta-analysis was developed to combine the results from multiple iTRAQ experiments. Analysis of a network of proteins involved in cardiovascular system development and function showed that troponins were oppositely regulated by alcohol exposure in females (upregulated) vs. males (downregulated), and this effect was validated by Western blot analysis. Pathway analysis also revealed that alcohol-consuming males showed increased expression of proteins involved in various steps of oxidative phosphorylation including complexes I, III, IV, and V, whereas females showed no change or decreased content. One implication from these findings is that females may be protected from the toxic effects of alcohol due to their ability to maintain contractile function, maintain efficiency of force generation, and minimize oxidative stress. However, the alcohol-induced insult may lead to increased production of reactive oxygen species and structural abnormalities in male myocardium.

The expression of PTHLH in human gastric mucosa enterochromaffin-like cells

BACKGROUND

Gastrectomy may disturb the body's mineral homeostasis, with osteopenia and osteoporosis being among the late outcomes. Parathyroid hormone-like hormone (PTHLH) was detected in rat gastric enterochromaffin-like (ECL) cells in 2005, and some researchers suggested that it was the hypothetical hormone gastrocalcin that is believed to lead to osteoporosis.

AIMS

Our objective was to learn whether PTHLH is expressed in human gastric ECL cells and to form a basic understanding about the relationship between PTHLH and gastrin.

METHODS

We collected normal human gastric mucosa specimens and serum samples from 28 patients.

RESULTS

RT-PCR and immunohistochemical analysis demonstrated weak expression of PTHLH in ECL cells at the RNA and protein levels. A low level of PTHLH expression was also found in the serum. Serum gastrin did have a significant positive correlation with the relative ratio of PTHLH mRNA to β-actin levels in gastric mucosa (rs=0.569, p=0.002).

CONCLUSIONS

This indicates that PTHLH has a low signal expression in human gastric ECL cells and that serum gastrin levels correlate with PTHLH RNA levels in gastric mucosa. Further work is needed to evaluate the functional role of PTHLH in ECL cells and to determine whether PTHLH is gastrocalcin.