Dipeptidyl peptidase 4 inhibitor attenuates obesity-induced myocardial fibrosis by inhibiting transforming growth factor-βl and Smad2/3 pathways in high-fat diet-induced obesity rat model

Phlorizin ameliorates myocardial fibrosis by inhibiting pyroptosis through restraining HK1-mediated NLRP3 inflammasome activation

The specific role of phlorizin (PHL), which has antioxidant, anti-inflammatory, hypoglycemic, antiarrhythmic and antiaging effects, on myocardial fibrosis (MF) and the related pharmacological mechanisms remain unknown. The objective of this study was to determine the protective actions of PHL on isoprenaline (ISO)-induced MF and its molecular mechanisms in mice. PHL was administered at 100 and 200 mg/kg for 15 consecutive days with a subcutaneous injection of ISO (10 mg/kg). MF was induced by ISO and alleviated by treatment with PHL, as shown by reduced fibrin accumulation in the myocardial interstitium and decreased levels of myocardial enzymes, such as creatinine kinase-MB, lactate dehydrogenase, and aspartate transaminase. In addition, PHL significantly decreased the expression of the fibrosis-related factors alpha smooth muscle actin, collagen I, and collagen III induced by ISO. The generation of intracellular reactive oxygen species induced by ISO was attenuated after PHL treatment. The malondialdehyde level was reduced, whereas the levels of superoxide dismutase, catalase, and glutathione were elevated with PHL administration. Moreover, compared to ISO, the level of Bcl-2 was increased and the level of Bax protein was decreased in the PHL groups. PHL relieved elevated TNF-α, IL-1β, and IL-18 levels as well as cardiac mitochondrial damage resulting from ISO. Further studies showed that PHL downregulated the high expression of hexokinase 1 (HK1), NLRP3, ASC, Caspase-1, and GSDMD-N caused by ISO. In conclusion, our findings suggest that PHL protects against ISO-induced MF due to its antioxidant, anti-apoptotic, and anti-inflammatory activities and via inhibition of pyroptosis mediated by the HK1/NLRP3 signaling pathway in vivo.

An Overview of the Cardioprotective Effects of Novel Antidiabetic Classes: Focus on Inflammation, Oxidative Stress, and Fibrosis

Metabolic diseases, particularly diabetes mellitus (DM), are significant global public health concerns. Despite the widespread use of standard-of-care therapies, cardiovascular disease (CVD) remains the leading cause of death among diabetic patients. Early and evidence-based interventions to reduce CVD are urgently needed. Large clinical trials have recently shown that sodium-glucose cotransporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP-1RA) ameliorate adverse cardiorenal outcomes in patients with type 2 DM. These quite unexpected positive results represent a paradigm shift in type 2 DM management, from the sole importance of glycemic control to the simultaneous improvement of cardiovascular outcomes. Moreover, SGLT2i is also found to be cardio- and nephroprotective in non-diabetic patients. Several mechanisms, which may be potentially independent or at least separate from the reduction in blood glucose levels, have already been identified behind the beneficial effect of these drugs. However, there is still much to be understood regarding the exact pathomechanisms. This review provides an overview of the current literature and sheds light on the modes of action of novel antidiabetic drugs, focusing on inflammation, oxidative stress, and fibrosis.

Long noncoding TSI attenuates aortic valve calcification by suppressing TGF-β1-induced osteoblastic differentiation of valve interstitial cells

INTRODUCTION

Calcific aortic valve disease (CAVD) is an active and cellular-driven fibrocalcific process characterised by differentiation of valve interstitial cells (VICs) towards an osteogenic-like phenotype. A recently identified lncRNA, lncTSI, has been reported to inhibit fibrogenesis through transforming growth factor (TGF)-β/Smad3 pathway. Here, the present study aimed to investigate the role of lncTSI in CAVD.

METHODS

The effect of TGF-β1 on lncTSI of VICs was measured. TGF-β1, RUNX2 and collagen I expression between calcified aortic valve tissue and normal samples by immunohistochemistry and western blotting. Human VICs were cultured and treated with TGF-β1. SiRNA and pcDNA3.1-lncTSI plasmid transfection were used to silence and overexpress lncTSI in VICs for 48 h, Smads phosphorylation, RUNX2 and collagen I expression were then verified by western blotting. In ApoE^-/- mice fed with 0.25 % high-cholesterol diet, AAV2-lncTSI were injected intravenously to observe their effect on the formation of aortic valve calcification.

RESULTS

lncTSI was highly expressed in VICs treated with TGF-β1. lncTSI was transcriptionally regulated by Smad3 and reversely inhibited TGF-β1-induced Smad3 phosphorylation and downregulated profibrotic gene expression. Silencing lncTSI increased TGF-β1-induced Smad3 phosphorylation, and subsequently, upregulated RUNX2 and collagen I expressions in VICs. While overexpression of lncTSI reversed the production of RUNX2 and collagen I in VICs. In a mouse CAVD model of 24 week 0.25 % high-cholesterol diet feeding, overexpression of lncTSI significantly reduced calcium deposition, RUNX2, pSmad3, and collagen I expression in aortic valve leaflets, with less aortic valve stenosis.

CONCLUSIONS

The novel findings of present study suggested that lncTSI alleviated aortic valve calcification through negative regulation of the TGF-β/Smad3 pathway. The results may help elucidate new diagnostic and therapeutic targets to prevent CAVD progression.

The emerging role of leptin in obesity-associated cardiac fibrosis: evidence and mechanism

Cardiac fibrosis is a hallmark of various cardiovascular diseases, which is quite commonly found in obesity, and may contribute to the increased incidence of heart failure arrhythmias, and sudden cardiac death in obese populations. As an endogenous regulator of adiposity metabolism, body mass, and energy balance, obesity, characterized by increased circulating levels of the adipocyte-derived hormone leptin, is a critical contributor to the pathogenesis of cardiac fibrosis. Although there are some gaps in our knowledge linking leptin and cardiac fibrosis, this review will focus on the interplay between leptin and major effectors involved in the pathogenesis underlying cardiac fibrosis at both cellular and molecular levels based on the current reports. The profibrotic effect of leptin is predominantly mediated by activated cardiac fibroblasts but may also involve cardiomyocytes, endothelial cells, and immune cells. Moreover, a series of molecular signals with a known profibrotic property is closely involved in leptin-induced fibrotic events. A more comprehensive understanding of the underlying mechanisms through which leptin contributes to the pathogenesis of cardiac fibrosis may open up a new avenue for the rapid emergence of a novel therapy for preventing or even reversing obesity-associated cardiac fibrosis.

Inhibition of SphK1/S1P Signaling Pathway Alleviates Fibrosis and Inflammation of Rat Myocardium after Myocardial Infarction

Objective

The sphingosine kinase 1 (SphK1)/sphingosine-1-phosphate (S1P) signaling pathway is involved in fibrosis and inflammatory responses of myocardial tissue after myocardial infarction (MI). The purpose of our study was to explore the role of SphK1/S1P signaling pathway in myocardial injury after MI.

Materials and Methods

We used Sprague-Dawley (SD) rats to make MI models and detected the changes of SphK1 and S1P in rats at 1, 7, and 14 days after MI. SphK1 inhibitor PF543 was used to treat MI rats, and we detected the changes in myocardial function and structure in rats by cardiac function test, 2,3,5-triphenyl tetrazolium staining, and histological staining. In addition, we used H₂O₂ to induce H9c2 cell injury to investigate the effect of PF543 on the viability of myocardial cells.

Results

Myocardial tissue lesions and fibrosis were observed at 7 and 14 days after MI, and the expressions of SphK1 and S1P in the injured myocardial tissues increased significantly in day 7 and day 14 in comparison to the control group. After treatment of MI rats with PF543, the structure of rat myocardial tissue was significantly improved and the degree of fibrosis was reduced. After MI, the expression of α-SMA and collagen I in the myocardium of rats was significantly increased while PF543 decreased their expression. PF543 also improved the cardiac function of MI rats and reduced the expression of IL-1β, IL-6, and TNF-α in the serum. PF543 also increased the viability of H9c2 cells in vitro.

Conclusions

The inhibition of the SphK1/S1P signaling pathway contributed to the relief of myocardial injury in MI rats. PF543 improved the myocardial structure and function of MI rats and reduced the level of fibrosis and inflammation in MI rats.

Linagliptin ameliorates pulmonary fibrosis in systemic sclerosis mouse model via inhibition of endothelial-to-mesenchymal transition

Systemic sclerosis (SSc) is a connective tissue disease that often causes pulmonary fibrosis. Dipeptidyl peptidase 4 (DPP4) inhibitor has shown anti-fibrotic properties in various fibrotic diseases. However, only two studies have reported its anti-fibrosis effects in pulmonary fibrosis, and the mechanism is not completely clear. In the present study, we further investigated the protective effects of linagliptin, a highly specific DPP4 inhibitor, on pulmonary fibrosis in SSc mouse model and the potential mechanisms. The results showed that linagliptin ameliorated pulmonary fibrosis in SSc mouse model, as evidenced by improved pathological changes of lung and body weight loss induced by BLM. Linagliptin also reduced BLM-induced oxidative stress, inflammation in lung in vivo. We revealed that linagliptin attenuated BLM-induced endothelial-to-mesenchymal transition (EndMT) in vitro and in vivo. BLM-induced enhanced migration ability of endothelial cells was also alleviated by linagliptin. Moreover, we confirmed that the Akt/mammalian target of rapamycin pathway was involved in BLM-induced EndMT in vivo, which was suppressed by linagliptin. In summary, we further confirmed the therapeutic effects of linagliptin on pulmonary fibrosis in SSc mouse model, which is based on its inhibitory effects on EndMT, oxidative stress, and inflammation.

The serine proteases dipeptidyl-peptidase 4 and urokinase are key molecules in human and mouse scar formation

Despite recent advances in understanding skin scarring, mechanisms triggering hypertrophic scar formation are still poorly understood. In the present study, we investigate mature human hypertrophic scars and developing scars in mice at single cell resolution. Compared to normal skin, we find significant differences in gene expression in most cell types present in scar tissue. Fibroblasts show the most prominent alterations in gene expression, displaying a distinct fibrotic signature. By comparing genes upregulated in murine fibroblasts during scar development with genes highly expressed in mature human hypertrophic scars, we identify a group of serine proteases, tentatively involved in scar formation. Two of them, dipeptidyl-peptidase 4 (DPP4) and urokinase (PLAU), are further analyzed in functional assays, revealing a role in TGFβ1-mediated myofibroblast differentiation and over-production of components of the extracellular matrix in vitro. Topical treatment with inhibitors of DPP4 and PLAU during scar formation in vivo shows anti-fibrotic activity and improvement of scar quality, most prominently after application of the PLAU inhibitor BC-11. In this study, we delineate the genetic landscape of hypertrophic scars and present insights into mechanisms involved in hypertrophic scar formation. Our data suggest the use of serine protease inhibitors for the treatment of skin fibrosis.

Insight into the Pro-inflammatory and Profibrotic Role of Macrophage in Heart Failure With Preserved Ejection Fraction

The prevalence of heart failure (HF) with preserved ejection fraction (HFpEF) is higher than that of HF with reduced/midrange ejection fraction (HFrEF/HFmrEF). However, no evidence-based guidelines for managing HFpEF have been generated. The current body of knowledge indicates that fibrosis and inflammation are important components of the cardiac remodeling process in HFpEF. In addition, macrophages potentially play an important role in pro-inflammatory and profibrotic processes in HFpEF patients, whereas HFpEF comorbidities could be a driving force for systemic microvascular inflammation and endothelial dysfunction. Under such circumstances, macrophages reportedly contribute to inflammation and fibrosis through 3 phases namely, inflammation, repair, and resolution. Signal transduction pathway-targeted therapies using animal experiments have generated important discoveries and breakthroughs for understanding the underlying mechanisms of HFpEF. However, only a handful of studies have reported promising results using human trials. Further investigations are therefore needed to elucidate the exact mechanisms underlying HFpEF and immune-pathogenesis of cardiac fibrosis.

CD26 as a target against fibrous formation in chronic airway rejection lesions

AIMS

Chronic lung allograft dysfunction (CLAD) after lung transplantation (Tx) is the clinical result of chronic airway rejection lesions (CARL), histomorphologically described as either obliterative remodeling of small airways or alveolar fibroelastosis, or as a combination of both. We here investigated the CD26-inhibitory effect on CD26-expressing CARL.

MAIN METHODS

CARL were induced by BALB/c → C57BL/6 mouse Tx under mild immunosuppression. CARL-related pro-fibrotic mediators were determined by RT-qPCR and western blotting (WB), EMT and ERK markers by WB. CD26 co-expression by immunofluorescence. CD26 was inhibited by Vildagliptin, gene depleted by CD26^-/- mice. Primary lung fibroblasts were employed for ex vivo analyses. Samples from lung transplant patients with CLAD were analyzed by immunohistochemistry.

KEY FINDINGS

CARL revealed a significantly higher expression of profibrotic proteins vs. normal lungs (p < 0.05). CD26 and EMT co-expressed in CARL with significantly higher Vimentin, Slug, Hif-1α, α-SMA expression vs. normal lungs (p < 0.05). Vildagliptin decreased the expression of α-SMA and N-cadherin in wild type (WT) lung fibroblasts (p < 0.05). Primary lung fibroblasts from WT and CD26^-/- mice treated with TGF-β1, IFN-γ, and FGF showed a reduction of EMT protein expression, proliferation, and reduced activation of ERK in CD26^-/- mice vs. WT mice. CD26-positive cells were found in patient samples with CLAD in areas of loose fibrosis, but not in areas of dense fibrosis.

SIGNIFICANCE

CD26 is expressed in CARL-developing lung transplants and CD26-inhibition downregulates fibrosis-forming mediators and fibroblast proliferation. CD26 thus qualifies as a target to attenuate the development of CARL mainly via modulation of ERK and the EMT pathway.

Molecular Mechanisms of Obesity-Linked Cardiac Dysfunction: An Up-Date on Current Knowledge

Obesity is defined as excessive body fat accumulation, and worldwide obesity has nearly tripled since 1975. Excess of free fatty acids (FFAs) and triglycerides in obese individuals promote ectopic lipid accumulation in the liver, skeletal muscle tissue, and heart, among others, inducing insulin resistance, hypertension, metabolic syndrome, type 2 diabetes (T2D), atherosclerosis, and cardiovascular disease (CVD). These diseases are promoted by visceral white adipocyte tissue (WAT) dysfunction through an increase in pro-inflammatory adipokines, oxidative stress, activation of the renin-angiotensin-aldosterone system (RAAS), and adverse changes in the gut microbiome. In the heart, obesity and T2D induce changes in substrate utilization, tissue metabolism, oxidative stress, and inflammation, leading to myocardial fibrosis and ultimately cardiac dysfunction. Peroxisome proliferator-activated receptors (PPARs) are involved in the regulation of carbohydrate and lipid metabolism, also improve insulin sensitivity, triglyceride levels, inflammation, and oxidative stress. The purpose of this review is to provide an update on the molecular mechanisms involved in obesity-linked CVD pathophysiology, considering pro-inflammatory cytokines, adipokines, and hormones, as well as the role of oxidative stress, inflammation, and PPARs. In addition, cell lines and animal models, biomarkers, gut microbiota dysbiosis, epigenetic modifications, and current therapeutic treatments in CVD associated with obesity are outlined in this paper.

TGF-β: The missing link in obesity-associated airway diseases?

Obesity is emerging as a global public health epidemic. The co-morbidities associated with obesity significantly contribute to reduced quality of life, mortality, and global healthcare burden. Compared to other asthma comorbidities, obesity prominently engenders susceptibility to inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease (COPD), contributes to greater disease severity and evokes insensitivity to current therapies. Unlike in other metabolic diseases associated with obesity, the mechanistic link between obesity and airway diseases is only poorly defined. Transforming growth factor-β (TGF-β) is a pleiotropic inflammatory cytokine belonging to a family of growth factors with pivotal roles in asthma. In this review, we summarize the role of TGF-β in major obesity-associated co-morbidities to shed light on mechanisms of the diseases. Literature evidence shows that TGF-β mechanistically links many co-morbidities with obesity through its profibrotic, remodeling, and proinflammatory functions. We posit that TGF-β plays a similar mechanistic role in obesity-associated inflammatory airway diseases such as asthma and COPD. Concerning the role of TGF-β on metabolic effects of obesity, we posit that TGF-β has a similar mechanistic role in obesity-associated inflammatory airway diseases in interplay with different comorbidities such as hypertension, metabolic diseases like type 2 diabetes, and cardiomyopathies. Future studies in TGF-β-dependent mechanisms in obesity-associated inflammatory airway diseases will advance our understanding of obesity-induced asthma and help find novel therapeutic targets for prevention and treatment.

CD26 upregulates proliferation and invasion in keloid fibroblasts through an IGF-1-induced PI3K/AKT/mTOR pathway

Background

Keloid is a fibrotic dermal disease characterized by an abnormal increase in fibroblast proliferation and invasion. These pathological behaviours may be related to the heterogeneity of keloid fibroblasts (KFs); however, because of a lack of effective biomarkers for KFs it is difficult to study the underlying mechanism. Our previous studies revealed that the expansion of CD26⁺ KFs was responsible for increased keloid proliferation and invasion capabilities; the intrinsic relationship and mechanism between CD26 and keloid is therefore worthy of further investigation. The aim of this study was to explore molecular mechanisms in the process of CD26 upregulated KFs proliferation and invasion abilities, and provide more evidence for CD26 as an effective biomarker of keloid and a new clinical therapeutic target.

Methods

Flow cytometry was performed to isolate CD26⁺/CD26⁻ fibroblasts from KFs and normal fibroblasts. To generate stably silenced KFs for CD26 and insulin-like growth factor-1 receptor (IGF-1R), lentiviral particles encoding shRNA targeting CD26 and IGF-1R were used for transfection. Cell proliferations were analysed by cell counting kit-8 assay and 5-ethynyl-2′-deoxyuridine (EdU) incorporation assay. Scratching assay and transwell assay were used to assess cell migration and invasion abilities. To further quantify the regulatory role of CD26 expression in the relevant signalling pathway, RT-qPCR, western blot, ELISA, PI3K activity assay and immunofluorescence were used.

Results

Aberrant expression of CD26 in KFs was proven to be associated with increased proliferation and invasion of KFs. Furthermore, the role of the IGF-1/IGF-1 receptor axis was also studied in CD26 and was found to upregulate KF proliferation and invasion. The PI3K/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway was shown to affect CD26-regulated KF proliferation and invasion by increasing phosphorylation levels of S6 kinase and 4E-binding protein.

Conclusions

CD26 can be the effective biomarker for KFs, and its expression is closely related to proliferation and invasion in keloids through the IGF-1-induced PI3K/AKT/mTOR pathway. This work provides a novel perspective on the pathological mechanisms affecting KFs and therapeutic strategies against keloids.

Knockout of TRPV1 Exacerbates Ischemia-reperfusion-induced Renal Inflammation and Injury in Obese Mice

BACKGROUND/AIM

Transient receptor potential vanilloid type 1 (TRPV1) has anti-inflammatory properties. The present study aimed to investigate the role of TRPV1 in renal inflammatory responses and tissue injury following renal ischemia-reperfusion (I/R) in diet-induced obese mice.

MATERIALS AND METHODS

TRPV1 knockout and wild type mice were fed a normal or western diet (WD) for 23 weeks and were then subjected to renal I/R injury.

RESULTS

TRPV1 knockout mice showed enhanced WD-induced renal macrophage infiltration and collagen deposition. Knocking out TRPV1 exacerbated renal I/R-induced increase of malondialdehyde, interleukin-6, monocyte chemoattractant protein-1, and NF-ĸB in obese mice. Similar results were observed in the expression of phosphorylated Smad1 and Smad2/3. Blockade of calcitonin gene-related peptide (CGRP) receptors with CGRP8-37 worsened the I/R-induced renal inflammation and injury.

CONCLUSION

Our data indicate that preserving TRPV1 expression and function may prevent renal I/R injury in obesity likely through alleviating inflammatory responses.

Combined exposure of fine particulate matter and high-fat diet aggravate the cardiac fibrosis in C57BL/6J mice

Cardiac fibrosis is associated with fine particulate matter (PM_2.5) exposure. In addition, whether high-fat diet (HFD) could exacerbate the PM_2.5-induced cardiac injury was unevaluated. Thus, this study was aimed to investigate the combined effects of PM_2.5 and HFD on cardiac fibrosis. The echocardiography and histopathological analysis showed that co-exposure of PM_2.5 and HFD had a significant deleterious effect on both cardiac systolic and diastolic function accompanied the myofibril disorder and myocardial fibrosis in C57BL/6 J mice than exposed to PM_2.5 or HFD alone. The augmented oxidative damage and increased α-SMA area percentage were detected in heart tissue of mice exposed to PM_2.5 and HFD together. PM_2.5 upregulated the expressions of cardiac fibrosis-related special markers, including collagen-I, collagen-III, TGF-β1, p-Smad3 and total Smad3, which had more pronounced activations in co-exposure group. Meanwhile, the factorial analysis exhibited the synergistic interaction regarded to the combined exposure of PM_2.5 and HFD. Simultaneously, PM_2.5 and palmitic acid increased intracellular ROS generation and activated the TGF-β1/Smad3 signaling pathway in cardiomyocytes. While the ROS scavenger NAC had effectively attenuated the ROS level and suppressed the TGF-β1/Smad3 signaling pathway. Taken together, our results demonstrated combined exposure to PM_2.5 and HFD could aggravate cardiac fibrosis via activating the ROS/TGF-β1/Smad3 signaling pathway.

Dipeptidyl peptidase-4 inhibition improves endothelial senescence by activating AMPK/SIRT1/Nrf2 signaling pathway

Dipeptidyl peptidase-4 (DPP4) is elevated in numerous cardiovascular pathological processes and DPP4 inhibition is associated with reduced inflammation and oxidative stress. The aim of this study was to examine the role of DPP4 in endothelial senescence. Sprague-Dawley rats (24 months) were orally administrated saxagliptin (10 mg·kg^-1·d^-1), a DPP4 inhibitor, for 12 weeks in drinking water. Body weight, heart rate, blood glucose, and blood pressure were measured and vascular histological experiments were performed. In vitro studies were performed using H₂O₂-induced senescent human umbilical vein endothelial cells. Both in vivo and in vitro studies confirmed the elevation of DPP4 in senescent vascular endothelium, and inhibition or knockdown of DPP4 ameliorated endothelial senescence. In addition, DPP4 inhibition or silencing reduced endothelial oxidative stress levels in aging vasculature and senescent endothelial cells. Moreover, DPP4 inhibition or knockdown normalized the expression and phosphorylation of AMP-activated protein kinase-α (AMPKα) and sirtuin 1 (SIRT1) expression. Furthermore, the beneficial effects of DPP4 inhibition or knockdown on endothelial cell senescence were at least partly dependent on SIRT1 and Nrf2 activation. In conclusion, our study demonstrated that DPP4 inhibition or silencing ameliorated endothelial senescence both in vivo and in vitro by regulating AMPK/SIRT1/Nrf2. DPP4 may be a new therapeutic target to combat endothelial senescence.

Deletion of Smad3 prevents renal fibrosis and inflammation in type 2 diabetic nephropathy

BACKGROUND

Transforming growth factor (TGF)-β/Smad3 signaling is highly activated in kidneys of patients with type 2 diabetic nephropathy (T2DN), however, the precise role of Smad3 in the pathogenesis of diabetic nephropathy remains unclear.

METHODS

Smad3 knockout (KO)-db/db mice were generated by intercrossing of male and female double-heterozygous Smad3^+/- db/m mice. Renal functions including urinary albumin excretion and serum creatinine were determined. Renal histological injury including renal fibrosis and inflammation were examined by periodic acid Schiff (PAS), periodic acid-silver methenamine (PASM), and immunohistochemistry (IHC) staining.

RESULTS

Smad3 knockout (KO)-db/db mice were protected from the development of diabetic kidney injury, characterized by the normal levels of urinary albumin excretion and serum creatinine without any evidence for renal fibrosis and inflammation. In contrast, Smad3 wild-type (WT) db/db and Smad3^+/- db/db mice developed progressively decline in renal function over the 12 to 32-week time course, including increased microalbuminuria and elevated levels of serum creatinine. Pathologically, Smad3 WT db/db and Smad3^+/- db/db mice exhibited a marked deposition of collagen-I (colI), collagen-IV(col-IV), and an increased infiltration of F4/80⁺ macrophages in kidney. Mechanistically, Smad3 deficiency decreased the lncRNA Erbb4-IR transcription, while increased miR-29b transcription and therefore protected the kidney from progressive renal injury in db/db mice.

CONCLUSION

Results from this study imply that Smad3 may represent as a novel and effective therapeutic target for T2DN.

Urolithin B improves cardiac function and reduces susceptibility to ventricular arrhythmias in rats after myocardial infarction

Cardiac fibrosis and inflammation play critical roles in ventricular remodelling after myocardial infarction (MI). Urolithin B (UB), a metabolite of ellagitannin-rich foods, has various biological activities, but its effect on ventricular remodelling after MI has not been determined. The present study evaluated whether UB inhibited ventricular structural remodelling and decreased the occurrence of ventricular arrhythmias after MI. Sprague-Dawley (SD) rats underwent ligation of the left anterior descending coronary artery before randomization to receive phosphate-buffered saline (PBS) or UB at doses of 2.5 mg/kg/day and 5 mg/kg/day via intraperitoneal administration or sham ligation. Cardiac function was assessed using echocardiography, haemodynamic detection and brain natriuretic peptide (BNP) levels 2 weeks post-MI. Hearts were used for electrophysiological testing and molecular and histological analyses. UB (5 mg/kg/day) significantly protected against post-MI cardiac dysfunction. UB markedly reduced infarct areas and myocyte size and attenuated cardiac fibrosis and inflammation post-MI. UB decreased the incidence of ventricular tachycardia and ventricular fibrillation compared to the MI group. We determined that UB inhibited the phosphorylation of JAK2/STAT3 and Smad2/3 signalling molecules. Our data suggest that UB reduces the occurrence of malignant ventricular arrhythmias after MI, which is likely associated with attenuation of ventricular structural remodelling via inactivation of the JAK2/STAT3 and Smad2/3 signalling pathway.

Deciphering the functional heterogeneity of skin fibroblasts using single-cell RNA sequencing

Though skin fibroblasts (FB) are the main cell population within the dermis, the different skin FB subsets are not well characterized and the traditional classification into reticular and papillary FBs has little functional relevance. To fill the gap of knowledge on FB diversity in human skin, we performed single-cell RNA sequencing. Investigation of marker genes for the different skin cell subtypes revealed a heterogeneous picture of FBs. When mapping reticular and papillary FB markers, we could not detect cluster specificity, suggesting that these two populations show a higher transcriptional heterogeneity than expected. This finding was further confirmed by in situ hybridization, showing that DPP4 was expressed in both dermal layers. Our analysis identified six FB clusters with distinct transcriptional signatures. Importantly, we could demonstrate that in human skin DPP4⁺ FBs are the main producers of factors involved in extracellular matrix (ECM) assembly. In conclusion, we provide evidence that hitherto considered FB markers are not ideal to characterize skin FB subpopulations in single-cell sequencing analyses. The identification of DPP4⁺ FBs as the main ECM-producing cells in human skin will foster the development of anti-fibrotic treatments for the skin and other organs.

High fat diet downregulates regulatory T cells in the myocardium of spontaneous hypertensive rats

BACKGROUND AND AIM

Regulatory T cells (Tregs) play an important role in cardiovascular complications with the immune response. However, the role of Tregs in high fat diet (HFD)-induced myocardial fibrosis has not been fully elucidated to date. Therefore, we investigated whether HFD suppresses Tregs activation in the myocardium of spontaneously hypertensive rats (SHRs), which aggregates myocardial fibrosis.

METHODS AND RESULTS

Eight-week-old male SHRs were fed to either HFD or control diet (CHO) groups for 12 weeks. We measured Tregs (CD4+FoxP3+) in the heart and mediastinal lymph nodes (LNs). The flow cytometry analysis confirmed that SHR-HFD exhibited a decreased Tregs compared to that of SHR-CHO in the heart and mediastinal LNs. Furthermore, the CD4 and FoxP3 antigens were used in the immunofluorescence microscopy of Tregs in the heart tissues. In the heart, dual staining for the Treg population was increased more in SHR-CHO than it was in SHR-HFD rats. In line with these findings, SHR-HFD significantly exacerbated myocardial fibrosis.

CONCLUSION

We found that diet-induced obesity typically showed an exacerbated myocardial fibrosis and down-regulation of Tregs pathway in the heart and mediastinal LNs. Therefore, we suggest that the up-regulation of Tregs may be a promising therapeutic approach to preventing obesity induced heart failure.

CD26 expression is attenuated by TGF-β and SDF-1 autocrine signaling on stromal myofibroblasts in human breast cancers

Human breast carcinoma‐associated fibroblasts (CAFs) increasingly acquire both transforming growth factor‐β (TGF‐β) and stromal cell‐derived factor‐1 (SDF‐1) signaling in an autocrine fashion during tumor progression. Such signaling mediates activated myofibroblastic and tumor‐promoting properties in these fibroblasts. CD26/dipeptidyl peptidase‐4 is a serine protease that cleaves various chemokines including SDF‐1. Stromal CD26 expression is reportedly undetectable in human skin squamous cell carcinomas. However, whether stromal CD26 expression is also downregulated in human breast cancers and which stromal cells potentially lack CD26 expression remain elusive. To answer these questions, sections prepared from 239 human breast carcinomas were stained with antibodies against CD26 and α‐smooth muscle actin (α‐SMA), a marker for activated myofibroblasts. We found that tumor‐associated stroma involving α‐SMA‐positive myofibroblasts stained negative or negligible for CD26 in 118 out of 193 (61.1%) tumors, whereas noncancerous stromal regions of the breast showed considerable staining for CD26. This decreased stromal CD26 staining in tumors also tends to be associated with poor outcomes for breast cancer patients. Moreover, we demonstrated that CD26 staining is attenuated on stromal myofibroblasts in human breast cancers. Consistently, CD26 expression is significantly downregulated in cultured CAF myofibroblasts extracted from human breast carcinomas as compared to control human mammary fibroblasts. Inhibition of TGF‐β or SDF‐1 signaling in CAFs by shRNA clearly upregulated the CD26 expression. Taken together, these findings indicate that CD26 expression is attenuated by TGF‐β‐ and SDF‐1‐autocrine signaling on stromal myofibroblasts in human mammary carcinomas, and that decreased stromal CD26 expression has potential as a prognostic marker.

Expression of ADAMTS-1 mRNA in myocardium of viral heart disease mice and its clinical significance

The expression of ADAMTS-1 mRNA in myocardium of viral heart disease (VHD) mice was investigated to explore its role in myocardial fibrosis. A total of 150 purebred inbred Balb/c mice were used in this study. According to the principle of similar body weight, 50 mice were selected to make an acute viral myocarditis (VMC) animal model (acute VMC group), and 50 mice were selected to make a chronic VMC animal model (chronic VMC group), and the remaining 50 mice were selected as a control group. RT-qPCR was used to detect the relative expression of transforming growth factor-β1 (TGF-β1) mRNA and ADAMTS-1 mRNA in myocardial tissue of three groups of mice, and their relationship in myocardial fibrosis was analyzed. Compared with the control group, the collagen volume fraction (CVF) in the myocardial tissue of the acute VMC group was significantly increased, and the increase of CVF in the myocardial tissue of the chronic VMC group was the most significant (p<0.001). Compared with the control group, the relative expression of TGF-β1 mRNA and ADAMTS-1 mRNA in myocardial tissue of the mice in the acute and chronic VMC group were significantly increased (p<0.001). The relative expression of TGF-β1 mRNA and ADAMTS-1 mRNA in myocardial tissue of chronic VMC group was significantly higher than that of acute VMC group (p<0.001). Pearson's correlation test results showed that ADAMTS-1 mRNA was positively correlated with CVF and TGF-β1 mRNA, and the correlation coefficients were (r=0.351, p<0.01, r=0.401, p<0.01). ADAMTS-1 is involved in the occurrence and development of myocardial fibrosis, and it is positively correlated with CVF and TGF-β1. It may play a role in promoting myocardial fibrosis during the development of VHD. It can be used as a biological index for predicting myocardial fibrosis.