A comprehensive guide to western blotting for tendon research.

Tendons are classified as dense fibrous connective tissue. This fibrous composition poses challenges in protein extraction, particularly hindering the application of Western blotting techniques. Because of these challenges, it becomes necessary to implement additional steps and specific solutions to attain success in this methodology with the tissue in question. The objective of this article is to provide a detailed protocol, elucidating each step, and making it easily replicable for researchers. The study focused on the Achilles tendons of Sprague-Dawley rats, emphasizing the need for a tailored approach in working with this tissue. By addressing the nuances of protein extraction from the dense and fibrous tendons, our protocol aims to facilitate the reproducibility of Western blotting experiments, contributing to a better understanding of this tissue.

Association of pulmonary black carbon accumulation with cardiac fibrosis in residents of Sao Paulo, Brazil.

Evidence suggests that myocardial interstitial fibrosis, resulting from cardiac remodeling, may possibly be influenced by mechanisms activated through the inhalation of airborne pollutants. However, limited studies have explored the relationship between lifetime exposure to carbon-based particles and cardiac fibrosis, specially using post-mortem samples. This study examined whether long-term exposure to air pollution (estimated by black carbon accumulated in the lungs) is associated with myocardial fibrosis in urban dwellers of megacity of Sao Paulo. Data collection included epidemiological and autopsy-based approaches. Information was obtained by interviewing the next of kin and through the pathologist's report. The individual index of exposure to carbon-based particles, which we designed as the fraction of black carbon (FBC), was estimated through quantification of particles on the macroscopic lung surface. Myocardium samples were collected for histopathological analysis to evaluate the fraction of cardiac fibrosis. The association between cardiac fibrosis and FBC, age, sex, smoking status and hypertension was assessed by means of multiple linear regression models. Our study demonstrated that the association of FBC with cardiac fibrosis is influenced by smoking status and hypertension. Among hypertensive individuals, the cardiac fibrosis fraction tended to increase with the increase of the FBC in both groups of smokers and non-smokers. In non-hypertensive individuals, the association between cardiac fibrosis fraction and FBC was observed primarily in smokers. Long-term exposure to tobacco smoke and environmental particles may contribute to the cardiac remodeling response in individuals with pre-existing hypertension. This highlights the importance of considering hypertension as an additional risk factor for the health effects of air pollution on the cardiovascular system. Moreover, the study endorses the role of autopsy to investigate the effects of urban environment and personal habits in determining human disease.

Ablation of miRNA-22 protects against obesity-induced adipocyte senescence and ameliorates metabolic disorders in middle-aged mice.

High-fat diet (HFD) promotes obesity-related metabolic complications by activating cellular senescence in white adipose tissue (WAT). Growing evidence supports the importance of microRNA-22 (miR-22) in metabolic disorders and cellular senescence. Recently, we showed that miR-22 deletion attenuates obesity-related metabolic abnormalities. However, whether miR-22 mediates HFD-induced cellular senescence of WAT remains unknown. Here, we uncovered that obese mice displayed increased pri-miR-22 levels and cellular senescence in WAT. However, miR-22 ablation protected mice against HFD-induced WAT senescence. In addition, in vitro studies showed that miR-22 deletion prevented preadipocyte senescence in response to Doxorubicin (Doxo). Loss-of-function studies in vitro and in vivo revealed that miR-22 increases H2ax mRNA and γH2ax levels in preadipocytes and WAT without inducing DNA damage. Intriguingly, miR-22 ablation prevented HFD-induced increase in γH2ax levels and DNA damage in WAT. Similarly, miR-22 deletion prevented Doxo-induced increase in γH2ax levels in preadipocytes. Adipose miR-22 levels were enhanced in middle-aged mice fed a HFD than those found in young mice. Furthermore, miR-22 deletion attenuated fat mass gain and glucose imbalance induced by HFD in middle-aged mice. Overall, our findings indicate that miR-22 is a key regulator of obesity-induced WAT senescence and metabolic disorders in middle-aged mice.

Set7 deletion attenuates isoproterenol-induced cardiac fibrosis and delays cardiac dysfunction.

Cardiovascular diseases are the main cause of death worldwide. Recent studies have revealed the influence of histone-modifying enzymes in cardiac remodeling and heart dysfunction. The Set7 methyltransferase regulates the expression of several genes through the methylation of histones and modulates the activity of non-histone proteins. However, the role of Set7 in cardiac remodeling and heart dysfunction remains unknown. To address this question, wild-type (WT) and Set7 knockout (KO) male mice were injected with isoproterenol or saline. WT mice injected with isoproterenol displayed a decrease in Set7 activity in the heart. In addition, WT and Set7 KO mice injected with isoproterenol exhibited cardiac hypertrophy. Interestingly, Set7 deletion exacerbated cardiac hypertrophy in response to isoproterenol but attenuated myocardial fibrosis. Echocardiograms revealed that WT mice injected with isoproterenol had lowered ejection fractions and fractional shortening, and increased E'-wave deceleration time and E/A ratio compared with their controls. Conversely, Set7 KO mice did not show alteration in these parameters in response to isoproterenol. However, prolonged exposure to isoproterenol induced cardiac dysfunction both in WT and Set7 KO mice. Both isoproterenol and Set7 deletion changed the transcriptional profile of the heart. Moreover, Set7 deletion increased the expression of Pgc1α and mitochondrial DNA content in the heart, and reduced the expression of cellular senescence and inflammation markers in response to isoproterenol. Taken together, our data suggest that Set7 deletion attenuates isoproterenol-induced myocardial fibrosis and delays heart dysfunction, suggesting that Set7 plays an important role in cardiac remodeling and dysfunction in response to stress.

Aerobic exercise training combined or not with okra consumption as a strategy to prevent kidney changes caused by metabolic syndrome in Zucker rats.

The complications of Metabolic Syndrome (MetS) include kidney disease, and most dialysis patients are diagnosed with MetS. The benefit of exercise training (ET) for MetS treatment is already well defined in the literature, but the antidiabetic and antihyperlipidemic benefits of okra (O) have been discovered only recently. The aim of this study was to evaluate the effects of O and/or ET supplementation on renal function and histology; serum urea and creatinine value; inflammation (IL-6, IL-10, TNF-α) and oxidative stress in renal tissue. For this, 32 Zucker rats (fa/fa) were randomly separated into four groups of 8 animals each: Metabolic Syndrome (MetS), MetS + Okra (MetS + O), MetS + Exercise Training (MetS + ET), and MetS + Exercise Training and Okra (MetS + ET + O), and 8 Zucker lean (fa/+) rats comprised the Control group (CTL). Okra was administered by orogastric gavage 2x/day (morning and night, 100 mg/kg) and ET performed on the treadmill, at moderate intensity, 1h/day, 5x/week for 6 weeks. Although the renal function was not altered, the animals with MetS showed greater fibrotic deposition accompanied by a worse stage of renal injury, in addition to increased kidney weight. Although all interventions were beneficial in reducing fibrosis, only ET combined with O was able to improve the degree of renal tissue impairment. ET improved the anti-inflammatory status and reduced nitrite levels, but the combination of ET and O was more beneficial as regards catalase activity. Okra consumption alone did not promote changes in inflammatory cytokines and oxidative stress in the kidney. In conclusion, ET combined or not with O seems to be beneficial in preventing the progression of renal disease when renal function is not yet altered.

The endocrinological component and signaling pathways associated to cardiac hypertrophy.

Although myocardial growth corresponds to an adaptive response to maintain cardiac contractile function, the cardiac hypertrophy is a condition that occurs in many cardiovascular diseases and typically precedes the onset of heart failure. Different endocrine factors such as thyroid hormones, insulin, insulin-like growth factor 1 (IGF-1), angiotensin II (Ang II), endothelin (ET-1), catecholamines, estrogen, among others represent important stimuli to cardiomyocyte hypertrophy. Thus, numerous endocrine disorders manifested as changes in the local environment or multiple organ systems are especially important in the context of progression from cardiac hypertrophy to heart failure. Based on that information, this review summarizes experimental findings regarding the influence of such hormones upon signalling pathways associated with cardiac hypertrophy. Understanding mechanisms through which hormones differentially regulate cardiac hypertrophy could open ways to obtain therapeutic approaches that contribute to prevent or delay the onset of heart failure related to endocrine diseases.

Deficiency of MicroRNA miR-1954 Promotes Cardiac Remodeling and Fibrosis.

Background Cardiac fibrosis occurs because of disruption of the extracellular matrix network leading to myocardial dysfunction. Angiotensin II (AngII) has been implicated in the development of cardiac fibrosis. Recently, microRNAs have been identified as an attractive target for therapeutic intervention in cardiac pathologies; however, the underlying mechanism of microRNAs in cardiac fibrosis remains unclear. Next-generation sequencing analysis identified a novel characterized microRNA, miR-1954, that was significantly reduced in AngII-infused mice. The finding led us to hypothesize that deficiency of miR-1954 triggers cardiac fibrosis. Methods and Results A transgenic mouse was created using α-MHC (α-myosin heavy chain) promoter and was challenged with AngII infusion. AngII induced cardiac hypertrophy and remodeling. The in vivo overexpression of miR-1954 showed significant reduction in cardiac mass and blood pressure in AngII-infused mice. Further analysis showed significant reduction in cardiac fibrotic genes, hypertrophy marker genes, and an inflammatory gene and restoration of a calcium-regulated gene (Atp2a2 [ATPase sarcoplasmic/endoplasmic reticulum Ca2+ transporting 2]; also known as SERCA2), but no changes were observed in apoptotic genes. THBS1 (thrombospondin 1) is indicated as a target gene for miR-1954. Conclusions Our findings provide evidence, for the first time, that miR-1954 plays a critical role in cardiac fibrosis by targeting THBS1. We conclude that promoting the level of miR-1954 would be a promising strategy for the treatment of cardiac fibrosis.

Pleural anthracosis as an indicator of lifetime exposure to urban air pollution: An autopsy-based study in Sao Paulo.

Many studies have been conducted to evaluate the association between air pollution and adverse health effects using a wide variety of methods to assess exposure. However, the assessment of individual long-term exposure to ambient air pollution is a challenging task and has not been evaluated in a large autopsy study. Our goal was to investigate whether exposure to urban air pollution is associated to the degree of lung anthracosis, considering modifying factors such as personal habits, mobility patterns and occupational activities. We conducted a study in Sao Paulo, Brazil from February 2017 to June 2018, combining epidemiological, spatial analysis and autopsy-based approaches. Information about residential address, socio-demographic details, occupation, smoking status, time of residence in the city and time spent commuting was collected via questionnaires applied to the next-of-kin. Images of the pleura surface from upper and lower lobes were used to quantify anthracosis in the lungs. We used multiple regression models to assess the association between the amount of carbon deposits in human lungs, measured by the fraction of pleural anthracosis (FA), and potential explanatory variables. We analyzed 413 cases and our data showed that for each additional hour spent in daily commuting, the ratio FA/(1-FA) is multiplied by 1.05 (95% confidence interval: [1.02; 1.08]). The estimated coefficient for daily hours spent in traffic was not considerably affected by the inclusion of socio-demographic variables and smoking habits. We estimate a tobacco equivalent dose of 5 cigarettes per day in a city where annual PM2.5 concentration oscillates around 25 µg/m3. Pleural anthracosis is a potential index of lifetime exposure to traffic-derived air pollution.

AT1 receptor blockage impairs NF-κB activation mediated by thyroid hormone in cardiomyocytes.

We have previously demonstrated that calcium-binding protein S100A8 and myeloid differentiation factor-88 (MyD88) are important mediators of nuclear transcription factor kappa-B (NF-κB) activation in cardiomyocytes and that signalling molecules are involved in the hypertrophic response that is stimulated by thyroid hormones (TH). Angiotensin II (Ang II), the main active peptide of the renin-angiotensin system (RAS), binds to type 1 Ang II receptor (AT1R) and subsequently promotes cardiac hypertrophy and the inflammatory response with NF-κB activation underlying the cardiovascular effects. Considering the amount of evidence that RAS is an important mediator of TH actions on the cardiovascular system, we aimed to investigate whether cardiac expression of NF-κB and upstream associated molecules could be altered in hyperthyroidism, as well as whether AT1R could mediate the effects of TH on cardiac tissue and in cardiomyocytes in culture. Wistar rats were subjected to hyperthyroidism with or without the AT1R blocker losartan. The TH serum levels, haemodynamic parameters and cardiac mass were assessed to confirm the hyperthyroid status. The S100A8, MyD88 and nuclear NF-κB expression levels were increased in the hearts of the hyperthyroid rats, and the losartan treatment attenuated these TH effects. In addition, the cultured cardiomyocytes that had been stimulated with losartan exhibited blunted S100A8 upregulation and NF-κB activation compared with the TH-treated cells. Together, our results suggest that AT1R participates in TH-induced cardiac hypertrophy partly by mediating S100A8, MyD88 and NF-κB activation via TH. These findings indicate the important crosstalk between TH and RAS, highlighting the participation of AT1R in the triggered mechanisms of TH that contribute to the cardiac hypertrophy response.

S100A8/MYD88/NF-қB: a novel pathway involved in cardiomyocyte hypertrophy driven by thyroid hormone.

Recent studies have evidenced the involvement of inflammation-related pathways to the development of cardiac hypertrophy and other consequences on the cardiovascular system, including the calcium-binding protein S100A8. However, this has never been investigated in the thyroid hormone (TH)-prompted cardiac hypertrophy. Thus, we aimed to test whether S100A8 and related signaling molecules, myeloid differentiation factor-88 (MyD88) and nuclear factor kappa B (NF-қB), could be associated with the cardiomyocyte hypertrophy induced by TH. Our results demonstrate that the S100A8/MyD88/NF-қB signaling pathway is activated in cardiomyocytes following TH stimulation. The knockdown of S100A8 and MyD88 indicates the contribution of those molecules to cardiomyocyte hypertrophy in response to TH, as evaluated by cell surface area, leucine incorporation assay, and gene expression. Furthermore, S100A8 and MyD88 are crucial mediators of NF-қB activation, which is also involved in the hypertrophic growth of TH-treated cardiomyocytes. Supporting the in vitro data, the contribution of NF-қB for TH-induced cardiac hypertrophy is confirmed in vivo, by using transgenic mice with cardiomyocyte-specific suppression of NF-қB. These data identify a novel pathway regulated by TH that mediates cardiomyocyte hypertrophy. However, the potential role of this new pathway in short and long-term cardiac effects of TH remains to be further investigated. KEY MESSAGES: Inflammation-related signaling is activated by T3 in cardiomyocytes. S100A8 and MyD88 have a crucial role in cardiomyocyte hypertrophy by T3. S100A8 and MyD88 mediate NF-қB activation by T3. NF-қB contributes to T3-induced cardiac hypertrophy in vitro and in vivo.

M-protein is down-regulated in cardiac hypertrophy driven by thyroid hormone in rats.

Although it is well known that the thyroid hormone (T3) is an important positive regulator of cardiac function over a short term and that it also promotes deleterious effects over a long term, the molecular mechanisms for such effects are not yet well understood. Because most alterations in cardiac function are associated with changes in sarcomeric machinery, the present work was undertaken to find novel sarcomeric hot spots driven by T3 in the heart. A microarray analysis indicated that the M-band is a major hot spot, and the structural sarcomeric gene coding for the M-protein is severely down-regulated by T3. Real-time quantitative PCR-based measurements confirmed that T3 (1, 5, 50, and 100 physiological doses for 2 days) sharply decreased the M-protein gene and protein expression in vivo in a dose-dependent manner. Furthermore, the M-protein gene expression was elevated 3.4-fold in hypothyroid rats. Accordingly, T3 was able to rapidly and strongly reduce the M-protein gene expression in neonatal cardiomyocytes. Deletions at the M-protein promoter and bioinformatics approach suggested an area responsive to T3, which was confirmed by chromatin immunoprecipitation assay. Functional assays in cultured neonatal cardiomyocytes revealed that depletion of M-protein (by small interfering RNA) drives a severe decrease in speed of contraction. Interestingly, mRNA and protein levels of other M-band components, myomesin and embryonic-heart myomesin, were not altered by T3. We concluded that the M-protein expression is strongly and rapidly repressed by T3 in cardiomyocytes, which represents an important aspect for the basis of T3-dependent sarcomeric deleterious effects in the heart.

AMPK signaling pathway is rapidly activated by T3 and regulates the cardiomyocyte growth.

Previous studies have indicated that AMP-activated protein kinase (AMPK) plays a critical role in the control of cardiac hypertrophy mediated by different stimuli such as thyroid hormone (TH). Although the classical effects of TH mediating cardiac hypertrophy occur by transcriptional mechanisms, recent studies have identified other responses to TH, which are more rapid and take place in seconds or minutes evidencing that TH rapidly modulates distinct signaling pathway, which might contribute to the regulation of cardiomyocyte growth. Here, we evaluated the rapid effects of TH on AMPK signaling pathway in cultured cardiomyocytes and determined the involvement of AMPK in T3-induced cardiomyocyte growth. We found for the first time that T3 rapidly activated AMPK signaling pathway. The use of small interfering RNA against AMPK resulted in increased cardiomyocyte hypertrophy while the pharmacological stimulation of AMPK attenuated this process, demonstrating that AMPK contributes to regulation of T3-induced cardiomyocyte growth.

MiRNA-208a and miRNA-208b are triggered in thyroid hormone-induced cardiac hypertrophy - role of type 1 Angiotensin II receptor (AT1R) on miRNA-208a/α-MHC modulation.

Hyperthyroidism promotes cardiac hypertrophy and the Angiotensin type 1 receptor (AT1R) has been demonstrated to mediate part of this response. Recent studies have uncovered a potentially important role for the microRNAs (miRNAs) in the control of diverse aspects of cardiac function. Then, the objective of the present study was to investigate the action promoted by hyperthyroidism on ß-MHC/miR-208b expression and on α-MHC/miR-208a expression, as well as the possible contribution of the AT1R in this event. The findings of this study confirmed that AT1R is a key mediator of the cardiac hypertrophy induced by hyperthyroidism. Additionally, we demonstrated that like ß-MHC, miR-208b was down-regulated in the hyperthyroid group. Similarly, like the expression of its host gene, α-MHC, miR-208a expression was up-regulated in response to hyperthyroidism. Finally, our data suggest for the first time that AT1R mediates the hyperthyroidism-induced increase on cardiac miRNA-208a/α-MHC levels, while does not influence on the reduction of miRNA-208b/ß-MHC levels.

New insight into the mechanisms associated with the rapid effect of T3 on AT1R expression.

The angiotensin II type 1 receptor (AT1R) is involved in the development of cardiac hypertrophy promoted by thyroid hormone. Recently, we demonstrated that triiodothyronine (T3) rapidly increases AT1R mRNA and protein levels in cardiomyocyte cultures. However, the molecular mechanisms responsible for these rapid events are not yet known. In this study, we investigated the T3 effect on AT1R mRNA polyadenylation in cultured cardiomyocytes as well as on the expression of microRNA-350 (miR-350), which targets AT1R mRNA. The transcriptional and translational actions mediated by T3 on AT1R levels were also assessed. The total content of ubiquitinated proteins in cardiomyocytes treated with T3 was investigated. Our data confirmed that T3 rapidly raised AT1R mRNA and protein levels, as assessed by real-time PCR and western blotting respectively. The use of inhibitors of mRNA and protein synthesis prevented the rapid increase in AT1R protein levels mediated by T3. In addition, T3 rapidly increased the poly-A tail length of the AT1R mRNA, as determined by rapid amplification of cDNA ends poly-A test, and decreased the content of ubiquitinated proteins in cardiomyocytes. On the other hand, T3 treatment increased miR-350 expression. In parallel with its transcriptional and translational effects on the AT1R, T3 exerted a rapid posttranscriptional action on AT1R mRNA polyadenylation, which might be contributing to increase transcript stability, as well as on translational efficiency, resulting to the rapid increase in AT1R mRNA expression and protein levels. Finally, these results show, for the first time, that T3 rapidly triggers distinct mechanisms, which might contribute to the regulation of AT1R levels in cardiomyocytes.