Propionate functions as a feeding state-dependent regulatory metabolite to counter proinflammatory signaling linked to nutrient load and obesity

Generally, fasting and refeeding confer anti- and proinflammatory effects, respectively. In humans, these caloric-load interventions function, in part, via regulation of CD4+ T cell biology. However, mechanisms orchestrating this regulation remain incomplete. We employed integrative bioinformatics of RNA sequencing and high-performance liquid chromatography-mass spectrometry data to measure serum metabolites and gene expression of peripheral blood mononuclear cells isolated from fasting and refeeding in volunteers to identify nutrient-load metabolite-driven immunoregulation. Propionate, a short chain fatty acid (SCFA), and the SCFA-sensing G protein-coupled receptor 43 (ffar2) were coordinately and inversely regulated by fasting and refeeding. Propionate and free fatty acid receptor agonists decreased interferon-γ and interleukin-17 and significantly blunted histone deacetylase activity in CD4+ T cells. Furthermore, propionate blunted nuclear factor κB activity and diminished interleukin-6 release. In parallel, propionate reduced phosphorylation of canonical T helper 1 (TH1) and TH17 regulators, STAT1 and STAT3, respectively. Conversely, knockdown of free fatty acid receptors significantly attenuated the anti-inflammatory role of propionate. Interestingly, propionate recapitulated the blunting of CD4+ TH cell activation in primary cells from obese individuals, extending the role of this metabolite to a disease associated with low-grade inflammation. Together, these data identify a nutrient-load responsive SCFA-G protein-coupled receptor linked pathway to regulate CD4+ TH cell immune responsiveness.

Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome

Post-infectious myalgic encephalomyelitis/chronic fatigue syndrome (PI-ME/CFS) is a disabling disorder, yet the clinical phenotype is poorly defined, the pathophysiology is unknown, and no disease-modifying treatments are available. We used rigorous criteria to recruit PI-ME/CFS participants with matched controls to conduct deep phenotyping. Among the many physical and cognitive complaints, one defining feature of PI-ME/CFS was an alteration of effort preference, rather than physical or central fatigue, due to dysfunction of integrative brain regions potentially associated with central catechol pathway dysregulation, with consequences on autonomic functioning and physical conditioning. Immune profiling suggested chronic antigenic stimulation with increase in naïve and decrease in switched memory B-cells. Alterations in gene expression profiles of peripheral blood mononuclear cells and metabolic pathways were consistent with cellular phenotypic studies and demonstrated differences according to sex. Together these clinical abnormalities and biomarker differences provide unique insight into the underlying pathophysiology of PI-ME/CFS, which may guide future intervention.

Boosting NAD preferentially blunts Th17 inflammation via arginine biosynthesis and redox control in healthy and psoriasis subjects

To evaluate whether nicotinamide adenine dinucleotide-positive (NAD+) boosting modulates adaptive immunity, primary CD4+ T cells from healthy control and psoriasis subjects were exposed to vehicle or nicotinamide riboside (NR) supplementation. NR blunts interferon γ (IFNγ) and interleukin (IL)-17 secretion with greater effects on T helper (Th) 17 polarization. RNA sequencing (RNA-seq) analysis implicates NR blunting of sequestosome 1 (sqstm1/p62)-coupled oxidative stress. NR administration increases sqstm1 and reduces reactive oxygen species (ROS) levels. Furthermore, NR activates nuclear factor erythroid 2-related factor 2 (Nrf2), and genetic knockdown of nrf2 and the Nrf2-dependent gene, sqstm1, diminishes NR amelioratory effects. Metabolomics analysis identifies that NAD+ boosting increases arginine and fumarate biosynthesis, and genetic knockdown of argininosuccinate lyase ameliorates NR effects on IL-17 production. Hence NR via amino acid metabolites orchestrates Nrf2 activation, augments CD4+ T cell antioxidant defenses, and attenuates Th17 responsiveness. Oral NR supplementation in healthy volunteers similarly increases serum arginine, sqstm1, and antioxidant enzyme gene expression and blunts Th17 immune responsiveness, supporting evaluation of NAD+ boosting in CD4+ T cell-linked inflammation.

[Bromhexine is a potential drug for COVID-19; From hypothesis to clinical trials]

COVID-19 (novel coronavirus disease 2019), caused by the SARS-CoV-2 virus, has various clinical manifestations and several pathogenic pathways. Although several therapeutic options have been used to control COVID-19, none of these medications have been proven to be a definitive cure. Transmembrane serine protease 2 (TMPRSS2) is a protease that has a key role in the entry of SARS-CoV-2 into host cells. Following the binding of the viral spike (S) protein to the angiotensin-converting enzyme 2 (ACE2) receptors of the host cells, TMPRSS2 processes and activates the S protein on the epithelial cells. As a result, the membranes of the virus and host cell fuse. Bromhexine is a specific TMPRSS2 inhibitor that potentially inhibits the infectivity cycle of SARS-CoV-2. Moreover, several clinical trials are evaluating the efficacy of bromhexine in COVID-19 patients. The findings of these studies have shown that bromhexine is effective in improving the clinical outcomes of COVID-19 and has prophylactic effects by inhibiting TMPRSS2 and viral penetration into the host cells. Bromhexine alone cannot cure all of the symptoms of SARS-CoV-2 infection. However, it could be an effective addition to control and prevent the disease progression along with other drugs that are used to treat COVID-19. Further studies are required to investigate the efficacy of bromhexine in COVID-19.

Boosting NAD+ blunts toll-like receptor-4 induced type-I interferon in control and systemic lupus erythematosus monocytes

BACKGROUND

Fasting and NAD+-boosting compounds including NAD+ precursor nicotinamide riboside (NR) confer anti-inflammatory effects. However, the underlying mechanisms and therapeutic potential are incompletely defined.

METHODS

We explored the underlying biology in myeloid cells from healthy volunteers following in-vivo placebo or NR administration and subsequently tested the findings in-vitro in monocytes extracted from subjects with systemic lupus erythematosus (SLE).

RESULTS

RNA sequencing of unstimulated and lipopolysaccharide (LPS)-activated monocytes implicate NR in the regulation of autophagy and type I interferon signaling. In primary monocytes NR blunts LPS-induced IFNβ production and genetic or pharmacologic disruption of autophagy phenocopies this effect. Given NAD+ is a co-enzyme in oxidoreductive reactions, metabolomics was performed and identified that NR increased inosine level. Inosine supplementation similarly blunts autophagy and IFNβrelease. Finally, as SLE exhibits type I interferon dysregulation, we assessed the NR effect on SLE patient monocytes and found that NR reduces autophagy and interferon-β release.

CONCLUSION

We conclude that NR, in an NAD+-dependent manner and in part via inosine-signaling, mediates suppression of autophagy and attenuates type I interferon in myeloid cells and identifies NR as a potential adjunct for SLE management.

TRIAL REGISTRATION

ClinicalTrails.gov registration numbers: NCT02812238, NCT00001846 and NCT00001372.

FUNDING

This work was supported by the NHLBI and NIAMS Divisions of Intramural Research.

Fasting-induced FOXO4 blunts human CD4+ T helper cell responsiveness

Intermittent fasting blunts inflammation in asthma and rheumatoid arthritis, suggesting that fasting may be exploited as an immune-modulatory intervention. However, mechanisms underpinning anti-inflammatory effects of fasting remain poorly characterized. Here, we show that fasting in humans is sufficient to blunt CD4+ T helper cell responsiveness. RNA-seq and flow cytometric immunophenotyping of peripheral blood mononuclear cells (PBMCs) from volunteers subjected to overnight or 24-hour fasting, and 3-hours of refeeding implicate that fasting blunts CD4+ T helper cell activation and differentiation. Transcriptomic analysis reveal that the longer fast-duration has a more robust effect on CD4+ T cell biology. Through bioinformatic analyses, we identify the transcription factor FOXO4 and its canonical target FKBP5 as a potential fasting-responsive regulatory axis. Genetic gain- or loss-of-function of FOXO4 and FKBP5 is sufficient to modulate Th1 and Th17 cytokine production. Moreover, we find that fasting-induced or genetic overexpression of FOXO4 and FKBP5 is sufficient to downregulate mTORC1 signaling and suppress STAT1/3 activation. Our results identify FOXO4-FKBP5 as a novel fasting-induced, STAT-mediated, regulatory pathway to blunt human CD4+ T helper cell responsiveness.

Identification and Validation of Nutrient State-Dependent Serum Protein Mediators of Human CD4+ T Cell Responsiveness

Intermittent fasting and fasting mimetic diets ameliorate inflammation. Similarly, serum extracted from fasted healthy and asthmatic subjects' blunt inflammation in vitro, implicating serum components in this immunomodulation. To identify the proteins orchestrating these effects, SOMAScan technology was employed to evaluate serum protein levels in healthy subjects following an overnight, 24-h fast and 3 h after refeeding. Partial least square discriminant analysis identified several serum proteins as potential candidates to confer feeding status immunomodulation. The characterization of recombinant IGFBP1 (elevated following 24 h of fasting) and PYY (elevated following refeeding) in primary human CD4⁺ T cells found that they blunted and induced immune activation, respectively. Furthermore, integrated univariate serum protein analysis compared to RNA-seq analysis from peripheral blood mononuclear cells identified the induction of IL1RL1 and MFGE8 levels in refeeding compared to the 24-h fasting in the same study. Subsequent quantitation of these candidate proteins in lean versus obese individuals identified an inverse regulation of serum levels in the fasted subjects compared to the obese subjects. In parallel, IL1RL1 and MFGE8 supplementation promoted increased CD4⁺ T responsiveness to T cell receptor activation. Together, these data show that caloric load-linked conditions evoke serological protein changes, which in turn confer biological effects on circulating CD4⁺ T cell immune responsiveness.

Evaluation of the validity and reliability of the Persian version of the Eurocest Neurotoxic Symptoms Questionnaire

Introduction: Modified Euro Quest questionnaire to assess neurological and psychiatric effects caused by exposure to organic solvents is used. This study investigates the validity, reliability, and usability of the modified Euro Quest questionnaire in Iran. Materials and Methods: This cross-sectional descriptive study was conducted on 206 workers of color and textile industries. Modified Euro Quest questionnaire was translated into Persian by using the forward-backward translation standard method. To evaluate the content validity, convergent validity, internal consistency, and reliability of the questionnaire were used the index CVI, Pearson correlation coefficient, Cronbach's alpha, and test-retest. The convergent validity was compared, results of the questionnaire, with results of mini-mental state examination (MMSE) and Multidimensional Fatigue Inventory (MFI). Results: The relationship between the modified Euroquest questionnaire was compare with the MMSE test and the MFI's questionnaire, Pearson correlation coefficients, and the results showed in order - 0.86 and 0.65, which represents a significant inverse correlation between this questionnaire with MMSE test(p>0.001) And a moderate correlation with the MFI's questionnaire(p>0.001). Content validity index (CVI) and intraclass correlation coefficient (ICC) were obtained in order amounts of ≤0.79 and 0.92, which was acceptable. The final questionnaire, Cronbach's alpha coefficient, was calculated (α =0.84).  Conclusion: The modified Euroquest Persian version is a valuable tool to assess the neurological and psychological effects caused by exposure to organic solvents in Iranian workers. 

Network Analysis and Transcriptome Profiling Identify Autophagic and Mitochondrial Dysfunctions in SARS-CoV-2 Infection

Analyzing host cells' transcriptional response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection will help delineate biological processes underlying viral pathogenesis. First, analysis of expression profiles of lung cell lines A549 and Calu3 revealed upregulation of antiviral interferon signaling genes in response to all three SARS-CoV-2, MERS-CoV, or influenza A virus (IAV) infections. However, perturbations in expression of genes involved in inflammatory, mitochondrial, and autophagy processes were specifically observed in SARS-CoV-2-infected cells. Next, a validation study in infected human nasopharyngeal samples also revealed perturbations in autophagy and mitochondrial processes. Specifically, mTOR expression, mitochondrial ribosomal, mitochondrial complex I, lysosome acidification, and mitochondrial fission promoting genes were concurrently downregulated in both infected cell lines and human samples. SARS-CoV-2 infection impeded autophagic flux either by upregulating GSK3B in lung cell lines or by downregulating autophagy genes, SNAP29, and lysosome acidification genes in human samples, contributing to increased viral replication. Therefore, drugs targeting lysosome acidification or autophagic flux could be tested as intervention strategies. Finally, age-stratified SARS-CoV-2-positive human data revealed impaired upregulation of chemokines, interferon-stimulated genes, and tripartite motif genes that are critical for antiviral signaling. Together, this analysis has revealed specific aspects of autophagic and mitochondrial function that are uniquely perturbed in SARS-CoV-2-infected host cells.

Fasting-induced FOXO4 blunts human CD4+ T helper cell responsiveness

Intermittent fasting blunts inflammation in asthma¹ and rheumatoid arthritis², suggesting that fasting may be exploited as an immune-modulatory intervention. However, the mechanisms underpinning the anti-inflammatory effects of fasting are poorly characterized^3-5. Here, we show that fasting in humans is sufficient to blunt CD4⁺ T helper cell responsiveness. RNA sequencing and flow cytometry immunophenotyping of peripheral blood mononuclear cells from volunteers subjected to overnight or 24-h fasting and 3 h of refeeding suggest that fasting blunts CD4⁺ T helper cell activation and differentiation. Transcriptomic analysis reveals that longer fasting has a more robust effect on CD4⁺ T-cell biology. Through bioinformatics analyses, we identify the transcription factor FOXO4 and its canonical target FK506-binding protein 5 (FKBP5) as a potential fasting-responsive regulatory axis. Genetic gain- or loss-of-function of FOXO4 and FKBP5 is sufficient to modulate T_H1 and T_H17 cytokine production. Moreover, we find that fasting-induced or genetic overexpression of FOXO4 and FKBP5 is sufficient to downregulate mammalian target of rapamycin complex 1 signalling and suppress signal transducer and activator of transcription 1/3 activation. Our results identify FOXO4-FKBP5 as a new fasting-induced, signal transducer and activator of transcription-mediated regulatory pathway to blunt human CD4⁺ T helper cell responsiveness.

Relationship between plasma concentrations of estradiol-17β and progesterone and the distribution of epithelial and inflammatory cells in the external opening of the river buffaloes’ uterine cervix during the gestational period

Changes in the distribution of the epithelial and inflammatory cells in the external opening of the uterine cervix in river buffaloes at three different occasions during the gestation period were investigated by light microscopic evaluation of mucus smears prepared by wet swab sampling and Giemsa-stained. Forty five pregnant river buffaloes that were in the first (n=15), second (n=15) and third (n=15) approximately equal parts of their gestation period were sampled twice concurrently by individual wet swabs from the external opening of the uterine cervix. Five smears were prepared from each sample. Immediately after mucus sampling, blood samples were obtained from the jugular vein of each animal, centrifuged immediately and stored at -20 oC to assay the plasma levels of estradiol-17β and progesterone. The results showed that changes in the percentage of the vacuolated and non-vacuolated epithelial cells, lymphocytes, eosinophils, and basophils were not statistically significant between the groups, which suggests that as the pregnancy progressed, changes in the blood levels of estradiol-17β and progesterone had little or no effect on the distribution of these cells in the region, but changes in the percentage of neutrophils were statistically significant between the groups. It was also found that changes in the percentage of macrophages between the second and third trimesters of the gestation period were not significant, but the difference between the first and the other trimesters was statistically significant. It was concluded that the percentages of neutrophils and macrophages increase significantly as the plasma concentrations of progesterone decrease during the gestation.

Generation of two induced pluripotent stem cell lines (NHLBIi001-A and NHLBIi001-B) from a healthy Caucasian female volunteer with normal cardiac function

Human-derived induced pluripotent stem cells (iPSCs) have proven to be indispensable in cardiovascular drug development, disease modeling, and developmental biology research. For this reason, it is particularly useful to develop wild-type iPSC lines to be used in experimental or control conditions. Here, we present two such cell lines generated from a sample of peripheral blood mononuclear cells (PBMCs) from a healthy patient with normal cardiac function.

Parkin regulation of CHOP modulates susceptibility to cardiac endoplasmic reticulum stress

The regulatory control of cardiac endoplasmic reticulum (ER) stress is incompletely characterized. As ER stress signaling upregulates the E3-ubiquitin ligase Parkin, we investigated the role of Parkin in cardiac ER stress. Parkin knockout mice exposed to aortic constriction-induced cardiac pressure-overload or in response to systemic tunicamycin (TM) developed adverse ventricular remodeling with excessive levels of the ER regulatory C/EBP homologous protein CHOP. CHOP was identified as a Parkin substrate and its turnover was Parkin-dose and proteasome-dependent. Parkin depletion in cardiac HL-1 cells increased CHOP levels and enhanced susceptibility to TM-induced cell death. Parkin reconstitution rescued this phenotype and the contribution of excess CHOP to this ER stress injury was confirmed by reduction in TM-induced cell death when CHOP was depleted in Parkin knockdown cardiomyocytes. Isogenic Parkin mutant iPSC-derived cardiomyocytes showed exaggerated ER stress induced CHOP and apoptotic signatures and myocardium from subjects with dilated cardiomyopathy showed excessive Parkin and CHOP induction. This study identifies that Parkin functions to blunt excessive CHOP to prevent maladaptive ER stress-induced cell death and adverse cardiac ventricular remodeling. Additionally, Parkin is identified as a novel post-translational regulatory moderator of CHOP stability and uncovers an additional stress-modifying function of this E3-ubiquitin ligase.

Impact of education in promoting the knowledge of and attitude to HIV/AIDS prevention: a trial on 17,000 Iranian students

The aim of this study was to assess the impact of an educational course on knowledge and attitude of students regarding HIV/AIDS prevention in Tabriz, Iran. The study was conducted by self-assessment technique among university students before and after an educational training programme. The findings showed that the knowledge of students increased significantly ( P<0.05). The attitude to the problem also improved positively in the subjects ( P<0.05). It is concluded that short-term training courses and continuous educational programmes (i.e. peer education, etc.) should be provided to young students through the course materials in the universities and schools promoting the awareness and attitude to this ever-increasing health problem.

Design of an optofluidic biosensor using the slow-light effect in photonic crystal structures

The authors propose a biosensor architecture based on the selective infiltration of photonic crystal (PhC) structures. The proposed sensor consists of a ring cavity coupled to an optofluidic slow-light waveguide in a PhC platform. A high potential sensitivity of 293 nm/refractive index unit is numerically demonstrated, while maintaining an ultracompact footprint.

Analysis and assessment of ground-level ozone measured at two stations in Tehran

In this study, variations of ambient ozone level are thoroughly analysed according to the monitored data in a mixed residential, commercial and industrial city, Tehran, based on considering the meteorological factors. Ozone as a pollutant shows typical annual, weekly and diurnal cycles. This analysis has shown that the ozone level concentrations were below the WHO guidelines in Tehran during 2000-2003. The relation between ozone level at two different stations (Aghdasieh and Fatemi) is found (r = 0.51). The ozone level response to meteorological parameters is investigated. The results suggest that the ozone level is affected (positively or negatively) by meteorological conditions, e.g. relative humidity, solar radiation, air temperature, wind speed and wind direction.

Statistical models and time series forecasting of sulfur dioxide: a case study Tehran

This study performed a time-series analysis, frequency distribution and prediction of SO(2) levels for five stations (Pardisan, Vila, Azadi, Gholhak and Bahman) in Tehran for the period of 2000-2005. Most sites show a quite similar characteristic with highest pollution in autumn-winter time and least pollution in spring-summer. The frequency distributions show higher peaks at two residential sites. The potential for SO(2) problems is high because of high emissions and the close geographical proximity of the major industrial and urban centers. The ACF and PACF are nonzero for several lags, indicating a mixed (ARMA) model, then at Bahman station an ARMA model was used for forecasting SO(2). The partial autocorrelations become close to 0 after about 5 lags while the autocorrelations remain strong through all the lags shown. The results proved that ARMA (2,2) model can provides reliable, satisfactory predictions for time series.

Cochlear implantation in children with Jervell, Lange-Nielsen syndrome

Jervell, Lange-Nielsen syndrome is a condition that causes profound hearing loss and disruption of the normal cardiac rhythm. This disorder is a form of long QT syndrome, a cardiac disorder that causes the cardiac muscle to take longer than usual to recharge between beats. A retrospective case study was performed to document cochlear implantation in three profoundly deaf children (two of them siblings) with Jervell, Lange-Nielsen syndrome. We discuss diagnosis and management of this syndrome and also the long-term performance of cochlear implantation in these Iranian patients, referring especially to the role of the ENT specialist in diagnosis and treatment. The collected data show that cochlear implantation can be relatively safely performed in patients with Jervell, Lange-Nielsen syndrome and that these children received significant benefit from cochlear implantation.

Cochlear implantation in prelingually deaf persons with additional disability

Objectives: We aimed to identify the frequency with which the following conditions were present as a second disability in cochlear-implanted, prelingually deaf persons: mild and moderate mental retardation; learning disability; attention deficit/hyperactivity disorder; cerebral palsy; congenital blindness; and autism. We also aimed to document the development of auditory perception in patients having one of these additional disabilities.

Study design: A retrospective study was designed to pursue the above aims.

Methods: We examined the records of 398 cochlear-implanted, prelingually deaf patients who had received a cochlear implant at least one year previously. Patients were selected who showed a delay in motor, cognitive or emotional development. The selected cases were referred for psychological evaluation in order to identify patients with additional disabilities. We then compared these patients' auditory perception prior to and one year following cochlear implantation.

Results: A total of 60 (15 per cent) cochlear-implanted, prelingually deaf patients were diagnosed with additional disabilities. These were classified as: mild mental retardation in eight cases (13.33 per cent); moderate mental retardation in five (8.33 per cent); learning disability in 20 (33.33 per cent); attention deficit/hyperactivity disorder in 15 (25 per cent); cerebral palsy in five (8.33); congenital blindness in three (5 per cent); and autism in four (6.66 per cent). All patients showed significant development in speech perception, except for autistic and congenitally deaf-blind patients.

Conclusion: Although cochlear implantation is not contraindicated in prelingually deaf persons with additional disabilities, congenitally deaf-blind and autistic patients showed limited development in auditory perception as a main outcome of cochlear implantation. These patients require unique rehabilitation in order to achieve more auditory development.

Cochlear implantation in children with Waardenburg syndrome

Waardenburg syndrome is an autosomal-dominant trait resulting from mutations occurring in different genes. It is often characterized by varying degrees of: congenital hearing loss; dystopia canthorum; synophrys; broad nasal root; depigmentation of hair (white forelock), skin or both; and heterochromic or hypochromic irides. A retrospective case study was done to assess speech perception, speech production, general intelligence and educational setting in six profoundly hearing-impaired children with Waardenburg syndrome (four with type I, one with type II and one with type III) ranging in age from two years to 14 years, seven months (mean = six years, six months). None of the patients had malformation of the cochlea and were implanted using Nucleus 22/24 and Med-el combi40+. Five out of the six cases were of average intelligence and one had a borderline intelligence quotient. The follow-up period ranged from one year, 10 months to six years, six months (mean = three years, six months) after implantation. The evaluation of auditory perception in patients was accomplished using the Persian Auditory Perception Test for the Hearing-Impaired, a Persian Spondee words test and the Categories of Auditory Performance Index. The Speech Intelligibility Rating test was used to evaluate speech production ability. All the patients' speech perception and speech intelligibility capabilities improved considerably after receiving the implants, and they were able to be placed in regular educational settings. Patients used their cochlear-implant devices whenever awake, implying that they benefitted from the devices. We suggest that any further expansion of cochlear-implantation criteria in children include those with Waardenburg syndrome.

Adult murine skeletal muscle contains cells that can differentiate into beating cardiomyocytes in vitro

It has long been held as scientific fact that soon after birth, cardiomyocytes cease dividing, thus explaining the limited restoration of cardiac function after a heart attack. Recent demonstrations of cardiac myocyte differentiation observed in vitro or after in vivo transplantation of adult stem cells from blood, fat, skeletal muscle, or heart have challenged this view. Analysis of these studies has been complicated by the large disparity in the magnitude of effects seen by different groups and obscured by the recently appreciated process of in vivo stem-cell fusion. We now show a novel population of nonsatellite cells in adult murine skeletal muscle that progress under standard primary cell-culture conditions to autonomously beating cardiomyocytes. Their differentiation into beating cardiomyocytes is characterized here by video microscopy, confocal-detected calcium transients, electron microscopy, immunofluorescent cardiac-specific markers, and single-cell patch recordings of cardiac action potentials. Within 2 d after tail-vein injection of these marked cells into a mouse model of acute infarction, the marked cells are visible in the heart. By 6 d they begin to differentiate without fusing to recipient cardiac cells. Three months later, the tagged cells are visible as striated heart muscle restricted to the region of the cardiac infarct.

A population of primitive cells from adult murine skeletal muscle can develop into beating cardiomyocytes in vitro and can contribute to the repair of damaged heart in vivo

The overall pattern of cardiac contraction depends on a spatial gradient of myosin regulatory light chain phosphorylation

Evolution of the human heart has incorporated a variety of successful strategies for motion used throughout the animal kingdom. One such strategy is to add the efficiency of torsion to compression so that blood is wrung, as well as pumped, out of the heart. Models of cardiac torsion have assumed uniform contractile properties of muscle fibers throughout the heart. Here, we show how a spatial gradient of myosin light chain phosphorylation across the heart facilitates torsion by inversely altering tension production and the stretch activation response. To demonstrate the importance of cardiac light chain phosphorylation, we cloned a myosin light chain kinase from a human heart and have identified a gain-in-function mutation in two individuals with cardiac hypertrophy.

The stretch-activation response may be critical to the proper functioning of the mammalian heart

The "stretch-activation" response is essential to the generation of the oscillatory power required for the beating of insect wings. It has been conjectured but not previously shown that a stretch-activation response contributes to the performance of a beating heart. Here, we generated transgenic mice that express a human mutant myosin essential light chain derived from a family with an inherited cardiac hypertrophy. These mice faithfully replicate the cardiac disease of the patients with this mutant allele. They provide the opportunity to study the stretch-activation response before the hearts are distorted by the hypertrophic process. Studies disclose a mismatch between the physiologic heart rate and resonant frequency of the cardiac papillary muscles expressing the mutant essential light chain. This discordance reduces oscillatory power at frequencies that correspond to physiologic heart-rates and is followed by subsequent hypertrophy. It appears, therefore, that the stretch-activation response, first described in insect flight muscle, may play a role in the mammalian heart, and its further study may suggest a new way to modulate human cardiac function.

Mutations in either the essential or regulatory light chains of myosin are associated with a rare myopathy in human heart and skeletal muscle

The muscle myosins and hexomeric proteins consisting of two heavy chains and two pairs of light chains, the latter called essential (ELC) and regulatory (RLC). The light chains stabilize the long alpha helical neck of the myosin head. Their function in striated muscle, however, is only partially understood. We report here the identification of distinct missense mutations in a skeletal/ventricular ELC and RLC, each of which are associated with a rare variant of cardiac hypertrophy as well as abnormal skeletal muscle. We show that myosin containing the mutant ELC has abnormal function, map the mutant residues on the three-dimensional structure of myosin and suggest that the mutations disrupt the stretch activation response of the cardiac papillary muscles.