Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor Fn14 during cardiac remodelling in rats

Alpha-Ketoglutarate Regulates Tnfrsf12a/Fn14 Expression via Histone Modification and Prevents Cancer-Induced Cachexia

Previous studies have shown that inhibition of TNF family member FN14 (gene: TNFRSF12A) in colon tumors decreases inflammatory cytokine expression and mitigates cancer-induced cachexia. However, the molecular mechanisms underlying the regulation of FN14 expression remain unclear. Tumor microenvironments are often devoid of nutrients and oxygen, yet how the cachexic response relates to the tumor microenvironment and, importantly, nutrient stress is unknown. Here, we looked at the connections between metabolic stress and FN14 expression. We found that TNFRSF12A expression was transcriptionally induced during glutamine deprivation in cancer cell lines. We also show that the downstream glutaminolysis metabolite, alpha-ketoglutarate (aKG), is sufficient to rescue glutamine-deprivation-promoted TNFRSF12A induction. As aKG is a co-factor for histone de-methylase, we looked at histone methylation and found that histone H3K4me3 at the Tnfrsf12a promoter is increased under glutamine-deprived conditions and rescued via DM-aKG supplementation. Finally, expression of Tnfrsf12a and cachexia-induced weight loss can be inhibited in vivo by DM-aKG in a mouse cancer cachexia model. These findings highlight a connection between metabolic stress and cancer cachexia development.

Losartan improves intestinal mucositis induced by 5-fluorouracil in mice

Intestinal mucositis (IM) is a common side effect of 5-fluorouracil (5-FU)-based chemotherapy, which negatively impacts therapeutic outcomes and delays subsequent cycles of chemotherapy resulting in dose reductions and treatment discontinuation. In search of new pharmacological alternatives that minimize your symptoms, this work set out to study the effect of losartan (LOS), a receptor type I (AT1) angiotensin II antagonist, on intestinal mucositis induced by 5-FU. Intestinal mucositis was induced by a single intraperitoneal administration of 5-FU (450 mg/kg) in Swiss mice. Losartan (5, 25 or 50 mg/kg) or saline was orally administered 30 min before 5-FU and daily for 4 days. On 4th day, the animals were euthanized and segments of small intestine were collected to evaluate histopathological alterations (morphometric analysis), concentration of inflammatory cytokines, oxidative stress markers and genic expression of NF-κB p65, Fn-14 and TWEAK. Weight evaluation and changes in leukogram were also analyzed. 5-FU induced intense weight loss, leukopenia and reduction in villus height compared to saline group. Losartan (50 mg/kg) prevented 5-FU-induced inflammation by decreasing in the analyzed parameters compared to the 5-FU group. Our findings suggest that 50 mg/kg of losartan prevents the effects of 5-FU on intestinal mucosa in mice.

Empagliflozin Disrupts a Tnfrsf12a-Mediated Feed Forward Loop That Promotes Left Ventricular Hypertrophy

PURPOSE

Although the cardioprotective benefits of sodium-glucose cotransporter 2 (SGLT2) inhibitors are now widely appreciated, the mechanisms underlying these benefits remain unresolved. Tumor necrosis factor receptor superfamily member 12a (Tnfrsf12a) is a receptor for tumor necrosis factor superfamily member 12 (Tnfsf12). Tnfrsf12a is highly inducible and plays a key role in the development of cardiac hypertrophy and heart failure. Here we set out to determine if SGLT2 inhibition affects the Tnfsf12/Tnfrsf12a system in the stressed myocardium.

METHODS

C57BL/6N mice that had undergone sham or transverse aortic constriction (TAC) surgery were treated with either the SGLT2 inhibitor empagliflozin (400 mg/kg diet; 60-65 mg/kg/day) or standard chow alone and were followed for 8 weeks. Tnfrsf12a expression in mouse hearts was assessed by in situ hybridization, qRT-PCR, and immunoblotting.

RESULTS

Left ventricular (LV) mass, end-systolic volume, and end-diastolic volume were all increased in TAC mice and were significantly lower with empagliflozin. Myocyte hypertrophy and interstitial fibrosis in TAC hearts were similarly attenuated with empagliflozin. Tnfrsf12a expression was upregulated in mouse hearts following TAC surgery but not in the hearts of empagliflozin-treated mice. In cultured cardiomyocytes, Tnfrsf12a antagonism attenuated the increase in cardiomyocyte size that was induced by phenylephrine.

CONCLUSION

Empagliflozin attenuates LV enlargement in mice with hypertrophic heart failure. This effect may be mediated, at least in part, by a reduction in loading conditions which limits upregulation of the inducible, proinflammatory, and prohypertrophic TNF superfamily receptor, Tnfrsf12a. Disruption of the Tnfsf12/Tnfrsf12a feed forward system may contribute to the cardioprotective benefits of SGLT2 inhibition.

TWEAK-Fn14 as a common pathway in the heart and the kidneys in cardiorenal syndrome

There is a complex relationship between cardiac and renal disease, often referred to as the cardiorenal syndrome. Heart failure adversely affects kidney function, and both acute and chronic kidney disease are associated with structural and functional changes to the myocardium. The pathological mechanisms and contributing interactions that surround this relationship remain poorly understood, limiting the opportunities for therapeutic intervention. The cytokine tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor, fibroblast growth factor-inducible 14 (Fn14), are abundantly expressed in injured kidneys and heart. The TWEAK-Fn14 axis promotes responses that drive tissue injury such as inflammation, proliferation, fibrosis, and apoptosis, while restraining the expression of tissue protective factors such as the anti-aging factor Klotho and the master regulator of mitochondrial biogenesis peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). High levels of TWEAK induce cardiac remodeling, and promote inflammation, tubular and podocyte injury and death, fibroblast proliferation, and, ultimately, renal fibrosis. Accordingly, targeting the TWEAK-Fn14 axis is protective in experimental kidney and heart disease. TWEAK has also emerged as a biomarker of kidney damage and cardiovascular outcomes and has been successfully targeted in clinical trials. In this review, we update our current knowledge of the roles of the TWEAK-Fn14 axis in cardiovascular and kidney disease and its potential contribution to the cardiorenal syndrome. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Fibroblast growth factor-inducible 14 mediates macrophage infiltration in heart to promote pressure overload-induced cardiac dysfunction

AIMS

Heart failure (HF) is characterized by compromised cardiac structure and function. Previous work has identified a link between upregulation of pro-inflammatory cytokines and HF. Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a pro-inflammatory cytokine, which binds to fibroblast growth factor inducible 14 (Fn14), a ubiquitously expressed cell-surface receptor. The objective of this study was to investigate the role of TWEAK/Fn14 pathway in promoting cardiac inflammation under non ischemic stress conditions.

MAIN METHODS

Wild type (WT) and Fn14 knock out (Fn14^-/-) mice were subjected to pressure overload [transaortic constriction (TAC)] for 1 or 6 weeks. A subset of WT TAC animals were treated with the Fn14 antagonist L524-0366. Cardiac function was measured by echocardiography. Cardiac fibrosis and macrophage infiltration were quantified using immunohistochemistry and flow cytometry, respectively. Cardiac fibroblasts were isolated for quantifying TWEAK-induced chemokine release.

KEY FINDINGS

Fn14^-/- mice displayed improved cardiac function, reduced fibrosis and lower macrophage infiltration in heart compared to WT following TAC. L524-0366 mitigated maladaptive remodeling with TAC. TWEAK induced secretion of the pro-inflammatory chemokine, monocyte chemoattractant protein 1 from WT but not Fn14^-/- fibroblasts in vitro, in part through activation of non-canonical NF-κB signaling. Finally, Fn14 expression was increased in mouse following TAC and in human failing hearts.

SIGNIFICANCE

Our findings support an important role for the TWEAK/Fn14 promoting macrophage infiltration and fibrosis in heart under non-ischemic stress, with potential for therapeutic intervention to improve cardiac function in the setting of HF.

Tumor Necrosis Factor-Like Weak Inducer of Apoptosis (TWEAK)/Fibroblast Growth Factor-Inducible 14 (Fn14) Axis in Cardiovascular Diseases: Progress and Challenges

Cardiovascular diseases (CVD) are the leading cause of mortality in Western countries. CVD include several pathologies, such as coronary artery disease, stroke, peripheral artery disease, and aortic aneurysm, among others. All of them are characterized by a pathological vascular remodeling in which inflammation plays a key role. Interaction between different members of the tumor necrosis factor superfamily and their cognate receptors induce several biological actions that may participate in CVD. The cytokine tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its functional receptor, fibroblast growth factor-inducible 14 (Fn14), are abundantly expressed during pathological cardiovascular remodeling. The TWEAK/Fn14 axis controls a variety of cellular functions, such as proliferation, differentiation, and apoptosis, and has several biological functions, such as inflammation and fibrosis that are linked to CVD. It has been demonstrated that persistent TWEAK/Fn14 activation is involved in both vessel and heart remodeling associated with acute and chronic CVD. In this review, we summarized the role of the TWEAK/Fn14 axis during pathological cardiovascular remodeling, highlighting the cellular components and the signaling pathways that are involved in these processes.

Ginkgo Flavonol Glycosides or Ginkgolides Tend to Differentially Protect Myocardial or Cerebral Ischemia-Reperfusion Injury via Regulation of TWEAK-Fn14 Signaling in Heart and Brain

Shuxuening injection (SXNI), one of the pharmaceutical preparations of Ginkgo biloba extract, has significant effects on both ischemic stroke and heart diseases from bench to bedside. Its major active ingredients are ginkgo flavonol glycosides (GFGs) and ginkgolides (GGs). We have previously reported that SXNI as a whole protected ischemic brain and heart, but the active ingredients and their contribution to the therapeutic effects remain unclear. Therefore, we combined experimental and network analysis approach to further explore the specific effects and underlying mechanisms of GFGs and GGs of SXNI on ischemia–reperfusion injury in mouse brain and heart. In the myocardial ischemia–reperfusion injury (MIRI) model, pretreatment with GFGs at 2.5 ml/kg was superior to the same dose of GGs in improving cardiac function and coronary blood flow and reducing the levels of lactate dehydrogenase and aspartate aminotransferase in serum, with an effect similar to that achieved by SXNI. In contrast, pretreatment with GGs at 2.5 ml/kg reduced cerebral infarction area and cerebral edema similarly to that of SXNI but more significantly compared with GFGs in cerebral ischemia–reperfusion injury (CIRI) model. Network pharmacology analysis of GFGs and GGs revealed that tumor necrosis factor-related weak inducer of apoptosis (TWEAK)–fibroblast growth factor-inducible 14 (Fn14) signaling pathway as an important common mechanism but with differential targets in MIRI and CIRI. In addition, immunohistochemistry and enzyme linked immunosorbent assay (ELISA) assays were performed to evaluate the regulatory roles of GFGs and GGs on the common TWEAK–Fn14 signaling pathway to protect the heart and brain. Experimental results confirmed that TWEAK ligand and Fn14 receptor were downregulated by GFGs to mitigate MIRI in the heart while upregulated by GGs to improve CIRI in the brain. In conclusion, our study showed that GFGs and GGs of SXNI tend to differentially protect brain and heart from ischemia–reperfusion injuries at least in part by regulating a common TWEAK–Fn14 signaling pathway.

FN14 Signaling Plays a Pathogenic Role in a Mouse Model of Experimental Autoimmune Myocarditis

BACKGROUND

The pathogenesis of inflammatory cardiomyopathy is affected by the activation of autoimmune-mediated cascades. To study these cascades, we developed an experimental model of troponin I (TnI)-induced autoimmune myocarditis (EAM). One factor playing a pivotal role in the context of autoimmune disorders is the receptor fibroblast growth factor-inducible 14 (FN14). Thus, the impact of FN14 in the development of autoimmune myocarditis was investigated.

METHODS AND RESULTS

TnI-immunization led to a significantly increased myocardial FN14 mRNA and protein expression in wild-type (wt) mice. To investigate the precise role of FN14 in EAM, FN14 knockout (ko) and wt littermates were immunized with TnI or control buffer. The animals were evaluated for cardiac parameters and indicators of myocardial injury. FN14 deficiency resulted in better cardiac performance, less myocardial inflammation, fibrosis, and cardiac damage. A lower myocardial mRNA expression of inflammatory cytokines and chemokines as well as their receptors could be demonstrated in TnI-immunized FN14ko compared to wt mice also immunized with TnI. Western blot analysis revealed a contribution of nuclear factor kappa-light-chain-enhancer of activated B cells to FN14-induced signaling cascades.

CONCLUSIONS

In the pathogenesis of autoimmune myocarditis, the inflammatory response to cardiac injury is attenuated in FN14ko mice. Thus, inhibition of FN14 in patients might represent a novel therapeutic strategy in the treatment of inflammatory cardiomyopathy.

TWEAK promotes endothelial progenitor cell vasculogenesis to alleviate acute myocardial infarction via the Fn14-NF-κB signaling pathway

Acute myocardial infarction (AMI) remains one of the leading causes of mortality worldwide; however, endothelial progenitor cell (EPC) transplantation has been proposed as a promising treatment strategy for EPC. High levels of tumor necrosis factor-related weak inducer of apoptosis (TWEAK) have been reported in AMI, although its effect on EPCs has not been reported. In the present study, immunofluorescence and flow cytometry were performed to assess the effect of TWEAK in isolated mouse EPCs. Echocardiography was used to evaluate the cardiac function of murine hearts following EPC treatment in the AMI model, while collagen synthesis within the heart tissue was assessed using Masson's trichrome staining. A tube formation assay and Transwell migration assay were performed to investigate the effects of TWEAK on vessel formation and EPC migration in vitro. Angiogenesis and arteriogenesis were assessed in vivo using immunohistochemistry and western blotting was performed to determine the effect of TWEAK-mediated nuclear factor (NF)-κB pathway activation in EPCs. The results revealed that TWEAK promotes EPC migration, tube formation and viability in vitro. Furthermore, TWEAK treatment resulted in improved cardiac function, decreased heart collagen and vasculogenesis in mice with AMI, which was mediated by the TWEAK- fibroblast growth factor-inducible 14 (Fn14)-NF-κB signaling pathway, as determined using Fn14 small interfering (si)RNA and Bay 11–7082 (an NF-κB inhibitor). In summary, the results of the present study suggest that activation of the TWEAK-Fn14-NF-κB signaling pathway exerts a beneficial effect on EPCs for the treatment of AMI.

TWEAK/Fn14 mediates atrial-derived HL-1 myocytes hypertrophy via JAK2/STAT3 signalling pathway

Atrial myocyte hypertrophy is one of the most important substrates in the development of atrial fibrillation (AF). The TWEAK/Fn14 axis is a positive regulator of cardiac hypertrophy in cardiomyopathy. This study therefore investigated the effects of Fn14 on atrial hypertrophy and underlying cellular mechanisms using HL‐1 atrial myocytes. In patients with AF, Fn14 protein levels were higher in atrial myocytes from atrial appendages, and expression of TWEAK was increased in peripheral blood mononuclear cells, while TWEAK serum levels were decreased. In vitro, Fn14 expression was up‐regulated in response to TWEAK treatment in HL‐1 atrial myocytes. TWEAK increased the expression of ANP and Troponin T, and Fn14 knockdown counteracted the effect. Inhibition of JAK2, STAT3 by specific siRNA attenuated TWEAK‐induced HL‐1 atrial myocytes hypertrophy. In conclusion, TWEAK/Fn14 axis mediates HL‐1 atrial myocytes hypertrophy partly through activation of the JAK2/STAT3 pathway.

Mechanical stretch induced transcriptomic profiles in cardiac myocytes

Mechanical forces are able to activate hypertrophic growth of cardiomyocytes in the overloaded myocardium. However, the transcriptional profiles triggered by mechanical stretch in cardiac myocytes are not fully understood. Here, we performed the first genome-wide time series study of gene expression changes in stretched cultured neonatal rat ventricular myocytes (NRVM)s, resulting in 205, 579, 737, 621, and 1542 differentially expressed (>2-fold, P < 0.05) genes in response to 1, 4, 12, 24, and 48 hours of cyclic mechanical stretch. We used Ingenuity Pathway Analysis to predict functional pathways and upstream regulators of differentially expressed genes in order to identify regulatory networks that may lead to mechanical stretch induced hypertrophic growth of cardiomyocytes. We also performed micro (miRNA) expression profiling of stretched NRVMs, and identified that a total of 8 and 87 miRNAs were significantly (P < 0.05) altered by 1-12 and 24-48 hours of mechanical stretch, respectively. Finally, through integration of miRNA and mRNA data, we predicted the miRNAs that regulate mRNAs potentially leading to the hypertrophic growth induced by mechanical stretch. These analyses predicted nuclear factor-like 2 (Nrf2) and interferon regulatory transcription factors as well as the let-7 family of miRNAs as playing roles in the regulation of stretch-regulated genes in cardiomyocytes.

The role of the tumor necrosis factor (TNF)-related weak inducer of apoptosis (TWEAK) in offspring exposed to prenatal hypoxia

Exposure to prenatal hypoxia in rats leads to intrauterine growth restriction (IUGR), decreases fetal cardiomyocyte proliferation and increases the risk to develop cardiovascular diseases (CVD) later in life. The tumor necrosis factor-related weak inducer of apoptosis (TWEAK) induces cardiomyocyte proliferation through activation of the fibroblast growth factor-inducible molecule 14 (Fn-14) receptor. The TWEAK/Fn-14 pathway becomes quiescent shortly after birth, however, it becomes upregulated with CVD; suggesting that it could be a link between the increased susceptibility to CVD in pregnancies complicated by hypoxia/IUGR. We hypothesized that offspring exposed to prenatal hypoxia will exhibit reduced cardiomyocyte proliferation due to reduced Fn-14 expression and that the TWEAK/Fn-14 pathway will be expressed in those adult offspring. We exposed pregnant Sprague Dawley rats to control (21% oxygen) or hypoxic (11% oxygen) conditions from gestational days 15 to 21. Ventricular cardiomyocytes were isolated from male and female, control and hypoxic offspring at postnatal day 1. Proliferation was assessed in the presence or absence of r-TWEAK (72 h, 100 ng/ml). Prenatal hypoxia was not associated with differences in Fn-14 protein expression in either male or female offspring. Cardiomyocytes from prenatal hypoxic male, but not female, offspring had decreased proliferation compared with controls. Addition of r-TWEAK increased cardiomyocyte proliferation in all offspring. In adult offspring of all groups, the TWEAK/Fn-14 pathway was not detectable. Cardiomyocyte proliferation was reduced in only male offspring exposed to prenatal hypoxia but this was not due to changes in the Fn-14 pathway. Studies addressing other pathways associated with CVD and prenatal hypoxia are needed.

Role of Omentin, Vaspin, Cardiotrophin-1, TWEAK and NOV/CCN3 in Obesity and Diabetes Development

Adipose tissue releases bioactive mediators called adipokines. This review focuses on the effects of omentin, vaspin, cardiotrophin-1, Tumor necrosis factor-like Weak Inducer of Apoptosis (TWEAK) and nephroblastoma overexpressed (NOV/CCN3) on obesity and diabetes. Omentin is produced by the stromal-vascular fraction of visceral adipose tissue. Obesity reduces omentin serum concentrations and adipose tissue secretion in adults and adolescents. This adipokine regulates insulin sensitivity, but its clinical relevance has to be confirmed. Vaspin is produced by visceral and subcutaneous adipose tissues. Vaspin levels are higher in obese subjects, as well as in subjects showing insulin resistance or type 2 diabetes. Cardiotrophin-1 is an adipokine with a similar structure as cytokines from interleukin-6 family. There is some controversy regarding the regulation of cardiotrophin-1 levels in obese -subjects, but gene expression levels of cardiotrophin-1 are down-regulated in white adipose tissue from diet-induced obese mice. It also shows anti-obesity and hypoglycemic properties. TWEAK is a potential regulator of the low-grade chronic inflammation characteristic of obesity. TWEAK levels seem not to be directly related to adiposity, and metabolic factors play a critical role in its regulation. Finally, a strong correlation has been found between plasma NOV/CCN3 concentration and fat mass. This adipokine improves insulin actions.

Mitogen-activated protein kinase p38 target regenerating islet-derived 3γ expression is upregulated in cardiac inflammatory response in the rat heart

Regenerating islet‐derived 3γ (Reg3γ) is a multifunctional protein, associated with various tissue injuries and inflammatory states. Since chronic inflammation is characteristics also for heart failure, the aim of this study was to characterize Reg3γ expression in cardiac inflammatory conditions. Reg3γ expression was studied in experimental rat models of myocardial infarction (MI) and pressure overload in vivo. For cell culture studies neonatal rat cardiac myocytes (NRCMs) were used. In addition, adenovirus‐mediated gene transfer of upstream mitogen‐activated protein kinase (MAPK) kinase 3b and p38α MAPK in vivo and in vitro was performed. Reg3γ mRNA (12.8‐fold, P < 0.01) and protein (5.8‐fold, P < 0.001) levels were upregulated during the postinfarction remodeling at day 1 after MI, and angiotensin II (Ang II) markedly increased Reg3γ mRNA levels from 6 h to 2 weeks. Immunohistochemistry revealed that the Ang II‐induced expression of Reg3γ was localized into the cardiac fibroblasts and myofibroblasts of the proliferating connective tissue in the heart. Stretching and treatments with endothelin‐1, lipopolysaccharide (LPS), and fibroblast growth factor‐1 increased Reg3γ mRNA levels in NRCMs. SB203580, a selective p38 MAPK inhibitor, markedly attenuated LPS and mechanical stretch‐induced upregulation of Reg3γ gene expression. Moreover, combined overexpression of MKK3bE and WT p38α increased Reg3γ gene expression in cultured cardiomyocytes in vitro and in the rat heart in vivo. Our study shows that cardiac stress activates Reg3γ expression and p38 MAPK is an upstream regulator of Reg3γ gene expression in heart. Altogether our data suggest Reg3γ is associated with cardiac inflammatory signaling.

TWEAK favors phosphate-induced calcification of vascular smooth muscle cells through canonical and non-canonical activation of NFκB

Vascular calcification (VC) is associated with increased cardiovascular mortality in aging, chronic kidney disease (CKD), type 2 diabetes mellitus (T2DM) and atherosclerosis. TNF-like weak inducer of apoptosis (TWEAK) recently emerged as a new biomarker for the diagnosis and prognosis of cardiovascular diseases. TWEAK binding to its functional receptor Fn14 was reported to promote several steps of atherosclerotic plaque progression. However, no information is currently available on the role of TWEAK/Fn14 on the development of medial calcification, which is highly prevalent in aging, CKD and T2DM. This study explored the involvement of TWEAK in human vascular smooth muscle cells (h-VSMCs) calcification in vitro. We report that TWEAK binding to Fn14 promotes inorganic phosphate-induced h-VSMCs calcification, favors h-VSMCs osteogenic transition, decreasing acta2 and myh11 and increasing bmp2 mRNA and tissue non-specific alkaline phosphatase (TNAP), and increases MMP9 activity. Blockade of the canonical NFκB pathway reduced by 80% TWEAK pro-calcific properties and decreased osteogenic transition, TNAP and MMP9 activity. Blockade of non-canonical NFκB signaling by a siRNA targeting RelB reduced by 20% TWEAK pro-calcific effects and decreased TWEAK-induced loss of h-VSMCs contractile phenotype and MMP9 activity, without modulating bmp2 mRNA or TNAP activity. Inhibition of ERK1/2 activation by a MAPK kinase inhibitor did not influence TWEAK pro-calcific properties. Our results suggest that TWEAK/Fn14 directly favors inorganic phosphate-induced h-VSMCs calcification by activation of both canonical and non-canonical NFκB pathways. Given the availability of neutralizing anti-TWEAK strategies, our study sheds light on the TWEAK/Fn14 axis as a novel therapeutic target in the prevention of VC.

TWEAK and NT-proBNP levels predict exercise capacity in hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is characterized by inappropriate hypertrophy, myocyte disarray and increased interstitial fibrosis. The tumour necrosis factor-like weak inducer of apoptosis (TWEAK) is a cell surface cytokine with biological activities including stimulation of cell growth, induction of inflammatory cytokines and stimulation of apoptosis. There are controversial data about the potential role of TWEAK in different cardiovascular pathologies. NT-proBNP is an established biomarker of myocardial wall stress, associated with poor functional class in HCM. We hypothesized that effort capacity in patients with HCM could be related to serum levels of these biomarkers.

MATERIALS AND METHODS

We included 40 haemodynamic stable HCM patients and 53 healthy controls with similar sex and age. We studied exercise capacity by maximal oxygen consumption in a limited treadmill exercise test. TWEAK and NT-proBNP were assayed by ELISA method and automated Elecsys® platform, respectively. We obtained 46 samples of myocardial tissues by septal myectomy in patients with HCM and evaluated myocardial fibrosis, immunoreaction with TWEAK antibody and apoptosis with TUNEL assay.

RESULTS

We found raised TWEAK and NT-proBNP serum levels in patients when compared with control levels (both P < 0.001). In a multivariate analysis, TWEAK and NT-proBNP levels, as well as sex, remained independently associated with the effort capacity (all P < 0.05). We found an association between immunoreaction degree and the degree of myocardial fibrosis (P = 0.021), as well as apoptosis (P = 0.002) in the tissue samples from patients undergoing septal myectomy.

CONCLUSIONS

TWEAK and NT-proBNP levels are biomarkers of disease severity independently associated with the effort capacity in patients with HCM.

TWEAK-Fn14 pathway activation after exercise in human skeletal muscle: insights from two exercise modes and a time course investigation

The cell surface receptor Fn14/TWEAKR was recently reported by our laboratory to be a prominent marker in the resistance exercise (RE) induced Transcriptome. The purpose of the present study was to extend our Transcriptome findings and investigate the gene and protein expression time course of markers in the TWEAK-Fn14 pathway following RE or run exercise (RUN). Vastus lateralis muscle biopsies were obtained from 6 RE subjects [25 ± 4 yr, 1-repetition maximum (RM): 99 ± 27 kg] pre- and 0, 1, 2, 4, 8, 12, and 24 h post RE (3 × 10 at 70% 1-RM). Lateral gastrocnemius biopsies were obtained from 6 RUN subjects [25 ± 4 yr, maximum oxygen uptake (V̇O2max): 63 ± 8 ml·kg(-1)·min(-1)] pre- and 0, 1, 2, 4, 8, 12, and 24 h after a 30-min RUN (75% V̇O2max). After RE, Fn14 gene and protein expression were induced (P < 0.05) and peaked at 8 and 12 h, respectively. Downstream markers analyzed showed evidence of TWEAK-Fn14 signaling through the alternative NF-κB pathway after RE. After RUN, Fn14 gene expression was induced (P < 0.05) to a much lesser extent and peaked at 24 h. Fn14 protein expression was only measurable on a sporadic basis, and there was weak evidence of alternative NF-κB pathway signaling after RUN. TWEAK gene and protein expression were not influenced by either exercise mode. These are the first human data to show a transient activation of the TWEAK-Fn14 axis in the recovery from exercise, and our data suggest the level of activation is exercise mode dependent. Furthermore, our collective data support a myogenic role for TWEAK-Fn14 through the alternative NF-κB pathway in human skeletal muscle.

Inter- not intraindividual differences in sTWEAK levels predict functional deterioration and mortality in patients with dilated cardiomyopathy

Background. TNF-like weak inducer of apoptosis (TWEAK) has been reported to predict mortality in patients with dilated cardiomyopathy. However, whether it can be used as a biomarker for disease monitoring or rather represents a risk factor for disease progression remains unclear. Aim of the Study. To evaluate the potential of sTWEAK as a biomarker in patients with dilated cardiomyopathy. Results. We conducted a serial study of sTWEAK levels in 78 patients with dilated cardiomyopathy. Soluble TWEAK levels predicted not only a combined mortality/heart transplantation endpoint after 4 years (P = 0.0001), but also the risk for clinical deterioration (P = 0.0001). Compared to NT-proBNP, sTWEAK remained relatively stable in individual patients on follow-up indicating that inter- rather than intraindividual differences in sTWEAK levels predicted outcome. Finally, neither did the scavenger receptor sCD163 correlate with sTWEAK levels nor did its determination add additional information on outcome in patients with dilated cardiomyopathy. Conclusion. Soluble TWEAK levels in patients with dilated cardiomyopathy may not be of value for disease monitoring but may represent a risk factor for disease progression and death. Further research will be necessary to elucidate the exact role of sTWEAK as a potential modulator of immune response in the setting of dilated cardiomyopathy.

Novel therapeutic strategies for cardioprotection

The morbidity and mortality from ischemic heart disease (IHD) remain significant worldwide. The treatment for acute myocardial infarction has improved over the past decades, including early reperfusion of occluded coronary arteries. Although it is essential to re-open the artery as soon as possible, paradoxically this leads to additional myocardial injury, called acute ischemia-reperfusion injury (IRI), for which currently no effective therapy is available. Therefore, novel therapeutic strategies are required to protect the heart from acute IRI in order to reduce myocardial infarction size, preserve cardiac function and improve clinical outcomes in patients with IHD. In this review article, we will first outline the pathophysiology of acute IRI and review promising therapeutic strategies for cardioprotection. These include novel aspects of mitochondrial function, epigenetics, circadian clocks, the immune system, microvesicles, growth factors, stem cell therapy and gene therapy. We discuss the therapeutic potential of these novel cardioprotective strategies in terms of pharmacological targeting and clinical application.

FGF1-mediated cardiomyocyte cell cycle reentry depends on the interaction of FGFR-1 and Fn14

Fibroblast growth factors (FGFs) signal through FGF receptors (FGFRs) mediating a broad range of cellular functions during embryonic development, as well as disease and regeneration during adulthood. Thus, it is important to understand the underlying molecular mechanisms that modulate this system. Here, we show that FGFR-1 can interact with the TNF receptor superfamily member fibroblast growth factor-inducible molecule 14 (Fn14) resulting in cardiomyocyte cell cycle reentry. FGF1-induced cell cycle reentry in neonatal cardiomyocytes could be blocked by Fn14 inhibition, while TWEAK-induced cell cycle activation was inhibited by blocking FGFR-1 signaling. In addition, costimulation experiments revealed a synergistic effect of FGF1 and TWEAK in regard to cardiomyocyte cell cycle induction via PI3K/Akt signaling. Overexpression of Fn14 with either FGFR-1 long [FGFR-1(L)] or FGFR-1 short [FGFR-1(S)] isoforms resulted after FGF1/TWEAK stimulation in cell cycle reentry of >40% adult cardiomyocytes. Finally, coimmunoprecipitation and proximity ligation assays indicated that endogenous FGFR-1 and Fn14 interact with each other in cardiomyocytes. This interaction was strongly enhanced in the presence of their corresponding ligands, FGF1 and TWEAK. Taken together, our data suggest that FGFR-1/Fn14 interaction may represent a novel endogenous mechanism to modulate the action of these receptors and their ligands and to control cardiomyocyte cell cycle reentry.

TNF-like weak inducer of apoptosis aggravates left ventricular dysfunction after myocardial infarction in mice

Background. TNF-like weak inducer of apoptosis (TWEAK) has recently been shown to be potentially involved in adverse cardiac remodeling. However, neither the exact role of TWEAK itself nor of its receptor Fn14 in this setting is known. Aim of the Study. To analyze the effects of sTWEAK on myocardial function and gene expression in response to experimental myocardial infarction in mice. Results. TWEAK directly suppressed the expression of PGC-1α and genes of oxidative phosphorylation (OXPHOS) in cardiomyocytes. Systemic sTWEAK application after MI resulted in reduced left ventricular function and increased mortality without changes in interstitial fibrosis or infarct size. Molecular analysis revealed decreased phosphorylation of PI3K/Akt and ERK1/2 pathways associated with reduced expression of PGC-1α and PPARα. Likewise, expression of OXPHOS genes such as atp5O, cycs, cox5b, and ndufb5 was also reduced. Fn14 −/− mice showed significantly improved left ventricular function and PGC-1α levels after MI compared to their respective WT littermates (Fn14 +/+). Finally, inhibition of intrinsic TWEAK with anti-TWEAK antibodies resulted in improved left ventricular function and survival. Conclusions. TWEAK exerted maladaptive effects in mice after myocardial infarction most likely via direct effects on cardiomyocytes. Analysis of the potential mechanisms revealed that TWEAK reduced metabolic adaptations to increased cardiac workload by inhibition of PGC-1α.

TWEAK-Fn14 Cytokine-Receptor Axis: A New Player of Myocardial Remodeling and Cardiac Failure

Tumor necrosis factor (TNF) has been firmly established as a pathogenic factor in heart failure, a significant socio-economic burden. In this review, we will explore the role of other members of the TNF/TNF receptor superfamily (TNFSF/TNFRSF) in cardiovascular diseases (CVDs) focusing on TWEAK and its receptor Fn14, new players in myocardial remodeling and heart failure. The TWEAK/Fn14 pathway controls a variety of cellular activities such as proliferation, differentiation, and apoptosis and has diverse biological functions in pathological mechanisms like inflammation and fibrosis that are associated with CVDs. Furthermore, it has recently been shown that the TWEAK/Fn14 axis is a positive regulator of cardiac hypertrophy and that deletion of Fn14 receptor protects from right heart fibrosis and dysfunction. We discuss the potential use of the TWEAK/Fn14 axis as biomarker for CVDs as well as therapeutic target for future treatment of human heart failure based on supporting data from animal models and in vitro studies. Collectively, existing data strongly suggest the TWEAK/Fn14 axis as a potential new therapeutic target for achieving cardiac protection in patients with CVDs.

Expression of tumor necrosis factor-like weak inducer of apoptosis and fibroblast growth factor-inducible 14 in patients with polymyositis and dermatomyositis

INTRODUCTION

The aim of this study was to investigate the expression of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor fibroblast growth factor-inducible 14 (Fn14) in patients with polymyositis (PM) and dermatomyositis (DM), and their relation to clinical manifestations.

METHODS

Serum levels of TWEAK were detected in 98 PM/DM patients and 37 healthy controls by using the ELISA method. Total RNA isolated from fresh-frozen muscle tissue samples of 36 PM/DM patients and 10 healthy controls were used for analyzing the mRNA levels of TWEAK and Fn14 by quantitative reverse transcription polymerase chain reaction (RT-PCR). Immunofluorescence staining of TWEAK and Fn14 was conducted on muscle biopsy specimens from 23 PM/DM patients and seven healthy controls.

RESULTS

Serum levels of TWEAK were significantly decreased in the PM/DM patients compared to those in the healthy controls (P < 0.001), and serum TWEAK levels negatively correlated with serum CD163 levels in PM/DM patients (r = -0.49, P < 0.001). The expression of Fn14 mRNA was significantly increased in the muscle tissue of PM/DM patients than in the muscle tissue of healthy controls (P < 0.01), whereas the expression of TWEAK mRNA in PM/DM patients was not statistically different from that of the healthy controls (P > 0.05). Fn14 mRNA levels in muscle tissue positively correlated with muscle disease activity (r = 0.512, P < 0.01). Patients with oropharyngeal dysphagia had significantly higher Fn14 mRNA levels than patients without oropharyngeal dysphagia (P < 0.05). The results of immunofluorescence staining showed that 19 out of 23 PM/DM patients were TWEAK-positive, and 20 out of 23 PM/DM patients were Fn14-positive. No detectable expressions of TWEAK or Fn14 were observed in the healthy controls.

CONCLUSIONS

TWEAK-Fn14 axis may be involved in the pathogenesis of PM/DM. Further understanding of TWEAK-Fn14 function in PM/DM may help to define therapeutic targets for PM/DM.

TWEAK/Fn14 Axis: A Promising Target for the Treatment of Cardiovascular Diseases

Cardiovascular diseases (CVD) are the first cause of mortality in Western countries. CVD include several pathologies such as coronary heart disease, stroke or cerebrovascular accident, congestive heart failure, peripheral arterial disease, and aortic aneurysm, among others. Interaction between members of the tumor necrosis factor (TNF) superfamily and their receptors elicits several biological actions that could participate in CVD. TNF-like weak inducer of apoptosis (TWEAK) and its functional receptor and fibroblast growth factor-inducible molecule 14 (Fn14) are two proteins belonging to the TNF superfamily that activate NF-κB by both canonical and non-canonical pathways and regulate several cell functions such as proliferation, migration, differentiation, cell death, inflammation, and angiogenesis. TWEAK/Fn14 axis plays a beneficial role in tissue repair after acute injury. However, persistent TWEAK/Fn14 activation mediated by blocking experiments or overexpression experiments in animal models has shown an important role of this axis in the pathological remodeling underlying CVD. In this review, we summarize the role of TWEAK/Fn14 pathway in the development of CVD, focusing on atherosclerosis and stroke and the molecular mechanisms by which TWEAK/Fn14 interaction participates in these pathologies. We also review the role of the soluble form of TWEAK as a biomarker for the diagnosis and prognosis of CVD. Finally, we highlight the results obtained with other members of the TNF superfamily that also activate canonical and non-canonical NF-κB pathway.

Deletion of Fn14 receptor protects from right heart fibrosis and dysfunction

Pulmonary arterial hypertension (PAH) is a fatal disease for which no cure is yet available. The leading cause of death in PAH is right ventricular (RV) failure. Previously, the TNF receptor superfamily member fibroblast growth factor-inducible molecule 14 (Fn14) has been associated with different fibrotic diseases. However, so far there is no study demonstrating a causal role for endogenous Fn14 signaling in RV or LV heart disease. The purpose of this study was to determine whether global ablation of Fn14 prevents RV fibrosis and remodeling improving heart function. Here, we provide evidence for a causative role of Fn14 in pulmonary artery banding (PAB)-induced RV fibrosis and dysfunction in mice. Fn14 expression was increased in the RV after PAB. Mice lacking Fn14 (Fn14^−/−) displayed substantially reduced RV fibrosis and dysfunction following PAB compared to wild-type littermates. Cell culture experiments demonstrated that activation of Fn14 induces collagen expression via RhoA-dependent nuclear translocation of myocardin-related transcription factor-A (MRTF-A)/MAL. Furthermore, activation of Fn14 in vitro caused fibroblast proliferation and myofibroblast differentiation, which corresponds to suppression of PAB-induced RV fibrosis in Fn14^−/− mice. Moreover, our findings suggest that Fn14 expression is regulated by endothelin-1 (ET-1) in cardiac fibroblasts. We conclude that Fn14 is an endogenous key regulator in cardiac fibrosis and suggest this receptor as potential new target for therapeutic interventions in heart failure.

Thrombospondin-4, tumour necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor Fn14: novel extracellular matrix modulating factors in cardiac remodelling

Cardiac remodelling is defined as changes in the size, shape, and function of the heart, which are most commonly caused by hypertension-induced left ventricular hypertrophy and myocardial infarction. Both neurohumoral and inflammatory factors have critical roles in the regulation of cardiac remodelling. A characteristic feature of cardiac remodelling is modification of the extracellular matrix (ECM), often manifested by fibrosis, a process that has vital consequences for the structure and function of the myocardium. In addition to established modulators of the ECM, the matricellular protein thrombospondin-4 (TSP-4) as well as the tumour necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor Fn14 has been recently shown to modulate cardiac ECM. TSP-4 null mice develop pronounced cardiac hypertrophy and fibrosis with defects in collagen maturation in response to pressure overload. TWEAK and Fn14 belong to the tumour necrosis factor superfamily of proinflammatory cytokines. Recently it was shown that elevated levels of circulating TWEAK via Fn14 critically affect the cardiac ECM, characterized by increasing fibrosis and cardiomyocyte hypertrophy in mice. Here we review the literature concerning the role of matricellular proteins and inflammation in cardiac ECM remodelling, with a special focus on TSP-4, TWEAK, and its receptor Fn14.

The role of TWEAK/Fn14 in cardiac remodeling

The pathophysiological basis of heart failure is cardiac remodeling, a process that comprises structural and functional changes including cardiomyocyte proliferation, hypertrophy, necrosis, apoptosis, autophagy, interstitial fibrosis, contractile dysfunction and ventricular dilatation. Accumulating evidence demonstrate that tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is involved in the process by binding its receptor fibroblast growth factor-inducible molecule 14 (Fn14). In this review, we will discuss the potential role of the TWEAK/Fn14 axis in cardiac remodeling, elucidate its possible mechanisms and explore new therapeutic targets for heart failure.

A Bioinformatics Resource for TWEAK-Fn14 Signaling Pathway

TNF-related weak inducer of apoptosis (TWEAK) is a new member of the TNF superfamily. It signals through TNFRSF12A, commonly known as Fn14. The TWEAK-Fn14 interaction regulates cellular activities including proliferation, migration, differentiation, apoptosis, angiogenesis, tissue remodeling and inflammation. Although TWEAK has been reported to be associated with autoimmune diseases, cancers, stroke, and kidney-related disorders, the downstream molecular events of TWEAK-Fn14 signaling are yet not available in any signaling pathway repository. In this paper, we manually compiled from the literature, in particular those reported in human systems, the downstream reactions stimulated by TWEAK-Fn14 interactions. Our manual amassment of the TWEAK-Fn14 pathway has resulted in cataloging of 46 proteins involved in various biochemical reactions and TWEAK-Fn14 induced expression of 28 genes. We have enabled the availability of data in various standard exchange formats from NetPath, a repository for signaling pathways. We believe that this composite molecular interaction pathway will enable identification of new signaling components in TWEAK signaling pathway. This in turn may lead to the identification of potential therapeutic targets in TWEAK-associated disorders.

TWEAK/Fn14 promotes the proliferation and collagen synthesis of rat cardiac fibroblasts via the NF-кB pathway

We wished to elucidate a potential role of the tumor necrosis factor-like weak inducer of apoptosis (TWEAK)/fibroblast growth factor-inducible molecule 14 (Fn14) axis in myocardial fibrosis. Stimulation of neonatal rat cardiac fibroblasts (CFs) with TWEAK could increase CFs numbers and collagen synthesis. Conversely, when CFs were pretreated with siRNA against Fn14, induction of cell proliferation and collagen synthesis by TWEAK were inhibited. Pretreatment with TWEAK on CFs induced activation of the nuclear factor-kappaB (NF-кB) pathway and subsequently increased the production of metalloproteinase-9 (MMP-9). Cell treatment with siRNA against Fn14 led to inhibition of the NF-кB pathway. Additionally, after stimulation of cell with ammonium pyrrolidine dithiocarbamate, cell proliferation and collagen synthesis induced by NF-кB and the upregulation of MMP-9 production were inhibited. The present study suggested that the TWEAK/Fn14 axis increased cell proliferation and collagen synthesis by activating the NF-кB pathway and increasing MMP-9 activity. This axis may be important for regulating myocardial fibrosis.

Transcriptome signature of resistance exercise adaptations: mixed muscle and fiber type specific profiles in young and old adults

This investigation examined the effects of acute resistance exercise (RE), progressive resistance training (PRT), and age on the human skeletal muscle Transcriptome. Two cohorts of young and old adults [study A: 24 yr, 84 yr (n = 28); study B: 25 yr, 78 yr (n = 36)] were studied. Vastus lateralis biopsies were obtained pre- and 4 h post-RE in conjunction with the 1st and 36th (last) training session as part of a 12-wk PRT program in study A, whereas biopsies were obtained in the basal untrained state in study B. Additionally, the muscle fiber type specific (MHC I and MHC IIa) Transcriptome response to RE was examined in a subset of young and old women from study A. Transcriptome profiling was performed using HG U133 Plus 2.0 Arrays. The main findings were 1) there were 661 genes affected by RE during the 1st and 36th training bout that correlated with gains in muscle size and strength with PRT (termed the Transcriptome signature of resistance exercise adaptations); 2) the RE gene response was most pronounced in fast-twitch (MHC IIa) muscle fibers and provided additional insight into the skeletal muscle biology affected by RE; 3) skeletal muscle of young adults is more responsive to RE at the gene level compared with old adults and age also affected basal level skeletal muscle gene expression. These skeletal muscle Transcriptome findings provide further insight into the molecular basis of sarcopenia and the impact of resistance exercise at the mixed muscle and fiber type specific level.

TWEAK, a multifunctional cytokine in kidney injury

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a cytokine of the TNF superfamily that activates the Fn14 receptor. TWEAK may regulate cell proliferation, cell death, cell differentiation, and inflammation. TWEAK and Fn14 are constitutively present in the kidney. Sources of TWEAK and Fn14 include intrinsic renal cells and infiltrating leukocytes. Basal Fn14 expression is low, but Fn14 is greatly upregulated during kidney injury. TWEAK contributes to kidney inflammation promoting chemokine secretion by renal cells through canonical and non-canonical NFκB activation. TWEAK also promotes tubular cell proliferation. However, TWEAK induces mesangial and tubular cell apoptosis under proinflammatory conditions. These data indicate that TWEAK is a multifunctional cytokine in the kidney, the actions of which are modulated by the cell microenvironment. Confirmation of the role of TWEAK in kidney injury came from functional studies in experimental animal models. The TWEAK/Fn14 pathway contributed to cell death and interstitial inflammation during acute kidney injury, to glomerular injury in lupus nephritis, to hyperlipidemia-associated kidney injury, and to tubular cell hyperplasia following unilateral nephrectomy. Circulating soluble TWEAK (sTWEAK) levels are a potential biomarker of adverse outcomes in chronic kidney disease and urinary sTWEAK is a potential biomarker of lupus nephritis activity. The available evidence suggests that TWEAK may provide diagnostic information and be a therapeutic target in renal injury. Its role in human kidney disease should be further explored.