Over-expression of growth differentiation factor 15 (GDF15) preventing cold ischemia reperfusion (I/R) injury in heart transplantation through Foxo3a signaling

GDF10 is a negative regulator of vascular calcification

Cardiovascular mortality is particularly high and increasing in patients with chronic kidney disease, with vascular calcification (VC) as a major pathophysiologic feature. VC is a highly regulated biological process similar to bone formation involving osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs). We have previously demonstrated that loss of T-cell death-associated gene 51 (TDAG51) expression leads to an attenuation of medial VC. We now show a significant induction of circulating levels of growth differentiation factor 10 (GDF10) in TDAG51-/- mice, which was of interest due to its established role as an inhibitor of osteoblast differentiation. The objective of this study was to examine the role of GDF10 in the osteogenic transdifferentiation of VSMCs. Using primary mouse and human VSMCs, as well as ex vivo aortic ring cultures, we demonstrated that treatment with recombinant human (rh) GDF10 mitigated phosphate-mediated hydroxyapatite (HA) mineral deposition. Furthermore, ex vivo aortic rings from GDF10-/- mice exhibited increased HA deposition compared to C57BL/6J controls. To explain our observations, we identified that rhGDF10 treatment reduced protein expression of runt-related transcription factor 2, a key driver of osteogenic transdifferentiation of VSMCs and VC. In support of these findings, in vivo treatment with rhGDF10 attenuated VD3-induced VC. Furthermore, we demonstrated an increase in circulating GDF10 in patients with chronic kidney disease with clinically defined severe VC, as assessed by coronary artery calcium score. Thus, our studies identify GDF10 as a novel inhibitor of mineral deposition and as such, may represent a potential novel biomarker and therapeutic target for the detection and management of VC.

Determination of Maximum Tolerable Cold Ischemia Time in a Mouse Model of Cervical Heterotopic Uterus Transplantation

BACKGROUND

Uterus transplantation (UTx) is an emerging treatment for uterine factor infertility. Determining the maximum tolerable cold ischemia time is crucial for successful UTx. However, the limit for cold ischemia in the uterus is unclear. This study aimed to examine cold ischemia's effects on mouse uteri and identify the maximum cold ischemia duration that uteri can endure.

METHODS

We systematically assessed the tolerance of mouse uteri to extended cold ischemia, 24 h, 36 h, and 48 h, using the cervical heterotopic UTx model. Multiple indicators were used to evaluate ischemia-reperfusion injury, including reperfusion duration, macroscopic examination, oxidative stress, inflammation, and histopathology. The function of transplants was evaluated through estrous cycle monitoring and embryo transfer.

RESULTS

Mouse uteri subjected to 48 h of cold ischemia exhibited significant delays and insufficiencies in reperfusion, substantial tissue necrosis, and loss of the estrous cycle. Conversely, uteri that underwent cold ischemia within 36 h showed long survival, regular estrous cycles, and fertility.

CONCLUSIONS

Our study demonstrated that mouse uteri can endure at least 36 h of cold ischemia, extending the known limits for cold ischemia and providing a pivotal reference for research on the prevention and treatment of cold ischemic injury in UTx.

GDF15 regulated by HDAC2 exerts suppressive effects on oxygen-glucose deprivation/reoxygenation-induced neuronal cell pyroptosis via the NLRP3 inflammasome

Background

Pyroptosis, inflammation-related programed cell death mediated by NLRP3 inflammasome, is involved in the pathogenesis of cerebral hypoxic-ischemic injury. Our study aims to explore the biological role of growth differentiation factor (GDF)15 in oxygen-glucose deprivation/reoxygenation (OGD/R)-induced neuronal pyroptosis.

Methods

HT22 neurons were subjected to OGD/R to simulate cerebral hypoxic-ischemic injury. Cells were transfected with plasmids to overexpress GDF15, or lentiviral-based shRNAs constructs to silence GDF15. ELISA assay was used to detect GDF15, IL-1β, IL-18, and neuron specific enolase (NSE) levels. Cell pyroptosis was measured by flow cytometery. Chromatin immunoprecipitation assay was used to detect interaction of H3K27ac with GDF15 promoter. GDF15, NLRP3, Caspase-1 p20 and GSDMD-N expressions were measured by Western blotting.

Results

Patients with malignant middle cerebral artery infarction showed decreased GDF15, but increased IL-1β, IL-18, and NSE levels in serum compared to healthy controls. OGD/R treatment caused significant increases in the levels of IL-1β, IL-18 and NSE, percentages of pyroptotic cells, and expressions of NLRP3, Caspase-1 p20, and GSDMD in HT22 cells, which were markedly reversed by GDF15 overexpression. However, GDF15 knockdown resulted in neuronal injury similar to those observed in OGD/R treatment. The GDF15 knockdown-induced effects were counteracted by treatment with NLRP3 inhibitor. OGD/R decreased the enrichment of H3K27ac in the promoter of GDF15 to down-regulate GDF15, but was compromised by co-treatment with HDAC2 inhibitor.

Conclusion

Our data demonstrates that GDF15 attenuates OGD/R-induced pyroptosis through NLRP3 inflammasome. HDAC2 is involved in mediating OGD-induced GDF15 down-regulation via H3K27ac modification. GDF15 overexpression and HDAC2 inhibition hold potential as useful therapeutic strategies for neuroprotection.

Growth/differentiation factor 15 (GDF15) expression in the heart after myocardial infarction and cardioprotective effect of pre-ischemic rGDF15 administration

Growth/differentiation factor-15 (GDF15) is considered an unfavourable prognostic biomarker for cardiovascular disease in clinical data, while experimental studies suggest it has cardioprotective potential. This study focuses on the direct cardiac effects of GDF15 during ischemia-reperfusion injury in Wistar male rats, employing concentrations relevant to patients at high cardiovascular risk. Initially, we examined circulating levels and heart tissue expression of GDF15 in rats subjected to ischemia-reperfusion and sham operations in vivo. We then evaluated the cardiac effects of GDF15 both in vivo and ex vivo, administering recombinant GDF15 either before 30 min of ischemia (preconditioning) or at the onset of reperfusion (postconditioning). We compared infarct size and cardiac contractile recovery between control and rGDF15-treated rats. Contrary to our expectations, ischemia-reperfusion did not increase GDF15 plasma levels compared to sham-operated rats. However, cardiac protein and mRNA expression increased in the infarcted zone of the ischemic heart after 24 h of reperfusion. Notably, preconditioning with rGDF15 had a cardioprotective effect, reducing infarct size both in vivo (65 ± 5% in control vs. 42 ± 6% in rGDF15 groups) and ex vivo (60 ± 4% in control vs. 45 ± 4% in rGDF15 groups), while enhancing cardiac contractile recovery ex vivo. However, postconditioning with rGDF15 did not alter infarct size or the recovery of contractile parameters in vivo or ex vivo. These novel findings reveal that the short-term exogenous administration of rGDF15 before ischemia, at physiologically relevant levels, protects the heart against ischemia-reperfusion injury in both in vivo and ex vivo settings. The ex vivo results indicate that rGDF15 operates independently of the inflammatory, endocrine and nervous systems, suggesting direct and potent cardioprotective properties against ischemia-reperfusion injury.

GDF15 restrains myocardial ischemia-reperfusion injury through inhibiting GPX4 mediated ferroptosis

BACKGROUND

Growth and differentiation factor 15 (GDF15) has been proved to regulate the process of Myocardial ischemia-reperfusion injury (MIRI), which is a serious complication of reperfusion therapy. The present study aimed to explore if GDF15 could regulate the MIRI-induced ferroptosis.

METHOD

MIRI animal model was established by ligating the left anterior descending coronary artery. Oxygen-glucose deprivation/reoxygenation (OGD/R) cell model was established to imitate MIRI in vitro. The indicators of ferroptosis including mitochondrial damage, GPX4, FACL4, XCT4, and oxidative stress markers were evaluated.

RESULTS

Overexpression of GDF15 greatly inhibited MIRI, improved cardiac function, alleviated MIRI-induced ferroptosis. pc-DNA-GDF15 significantly inhibited the oxidative stress condition and inflammation response. The OGD/R-induced ferroptosis was also inhibited by pc-DNA-GDF15.

CONCLUSION

We proved that the MIRI-induced ferroptosis could by inhibited by pc-DNA-GDF15 through evaluating mitochondrial damage, MDA, GSH, and GSSG. Our research provides a new insight for the prevention and treatment of MIRI, and a new understanding for the mechanism of MIRI-induced ferroptosis.

Circular RNA MAP2K2-modified immunosuppressive dendritic cells for preventing alloimmune rejection in organ transplantation

Long-term patient and graft survival has been achieved in organ transplantation but at the expense of toxic side effects that are associated with long-term use of nonspecific immunosuppressive drugs. Discovering new regulators of dendritic cells is the key for development of an ideal treatment to prevent immune rejection. We hypothesized that knockdown of circMAP2K2 induces immunosuppressive DCs and that treatment with circMAP2K2 silenced-DCs can prevent alloimmune rejection. DCs were cultured and transfected with siRNA for circMAP2K2. circMAP2K2 levels were measured by qRT-PCR. DC's maturation and immune function were assessed by flow cytometry and mixed lymphocyte reactions. The function of circMAP2K2 was illustrated by a series of RIP and IP. The therapeutics of engineered DCs was tested in a mouse heart transplantation model. We found that circMAP2K2 was highly expressed in mature DCs. Knockdown of circMAP2K2 reduced expression of MHCII, CD40 and CD80, attenuated the ability of DCs to activate allogeneic naïve T cells, and enhanced CD4+CD25+FOXP3+ regulatory T cells (Treg). circMAP2K2-induced immunosuppressive DCs by interacting with SENP3. Treatment with circMAP2K2-knockdown DCs attenuated alloimmune rejection and prolonged allograft survival in a murine heart transplantation model. The immune suppression induced in vivo was donor-antigen specific. In conclusion, knockdown of circMAP2K2 can induce immunosuppressive DCs which are able to inhibit overactive immune response, highlighting a new promising therapeutic approach for immune disorder diseases.

The forkhead box O3 (FOXO3): a key player in the regulation of ischemia and reperfusion injury

Forkhead box O3 is a protein encoded by the FOXO3 gene expressed throughout the body. FOXO3 could play a crucial role in longevity and many other pathologies, such as Alzheimer's disease, glioblastoma, and stroke. This study is a comprehensive review of the expression of FOXO3 under ischemia and reperfusion (IR) and the molecular mechanisms of its regulation and function. We found that the expression level of FOXO3 under ischemia and IR is tissue-specific. Specifically, the expression level of FOXO3 is increased in the lung and intestinal epithelial cells after IR. However, FOXO3 is downregulated in the kidney after IR and in the skeletal muscles following ischemia. Interestingly, both increased and decreased FOXO3 expression have been reported in the brain, liver, and heart following IR. Nevertheless, these contribute to stimulating ischemia and reperfusion injury via the induction of inflammatory response, apoptosis, autophagy, mitophagy, pyroptosis, and oxidative damage. These results suggest that FOXO3 could play protective effects in some organs and detrimental effects in others against IR injury. Most importantly, these findings indicate that controlling FOXO3 expression, genetically or pharmacologically, could contribute to preventing or treating ischemia and reperfusion damage.

Mitochondrial unfolded protein response in ischemia-reperfusion injury

Mitochondrial unfolded protein response (UPRmt) is a mitochondrial stress response that activates the transcriptional program of mitochondrial chaperone proteins and proteases to keep protein homeostasis in mitochondria. Ischemia-reperfusion injury results in multiple severe clinical issues linked to high morbidity and mortality in various disorders. The pathophysiology and pathogenesis of ischemia-reperfusion injury are complex and multifactorial. Emerging evidence showed the roles of UPRmt signaling in ischemia-reperfusion injury. Herein, we discuss the regulatory mechanisms underlying UPRmt signaling in C. elegans and mammals. Furthermore, we review the recent studies into the roles and mechanisms of UPRmt signaling in ischemia-reperfusion injury of the heart, brain, kidney, and liver. Further research of UPRmt signaling will potentially develop novel therapeutic strategies against ischemia-reperfusion injury.

The Potential Role of Growth Differentiation Factor 15 in COVID-19: A Corollary Subjective Effect or Not?

Coronavirus disease 2019 (COVID-19) is primarily caused by various forms of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) variants. COVID-19 is characterized by hyperinflammation, oxidative stress, multi-organ injury (MOI)-like acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Different biomarkers are used in the assessment of COVID-19 severity including D-dimer, ferritin, lactate dehydrogenase (LDH), and hypoxia-inducible factor (HIF). Interestingly, growth differentiation factor 15 (GDF15) has recently become a potential biomarker correlated with the COVID-19 severity. Thus, this critical review aimed to determine the critical association between GDF15 and COVID-19. The perfect function of GDF15 remains not well-recognized; nevertheless, it plays a vital role in controlling cell growth, apoptosis and inflammatory activation. Furthermore, GDF15 may act as anti-inflammatory and pro-inflammatory signaling in diverse cardiovascular complications. Furthermore, the release of GDF15 is activated by various growth factors and cytokines including macrophage colony-stimulating factor (M-CSF), angiotensin II (AngII) and p53. Therefore, higher expression of GDF15 in COVID-19 might a compensatory mechanism to stabilize and counteract dysregulated inflammatory reactions. In conclusion, GDF15 is an anti-inflammatory cytokine that could be associated with the COVID-19 severity. Increased GDF15 could be a compensatory mechanism against hyperinflammation and exaggerated immune response in the COVID-19. Experimental, preclinical and large-scale clinical studies are warranted in this regard.

Macrophage inhibitory cytokine-1 in cancer: Beyond the cellular phenotype

Despite technological advances in diagnostic abilities and improved treatment methods, the burden of cancers remains high, leading to significant morbidity and mortality. One primary reason is that cancer cell secretory factors modulate the tumor microenvironment, supporting tumor growth and circumvents anticancer activities of conventional therapies. Macrophage inhibitory cytokine-1 (MIC-1) is a pleiotropic cytokine elevated in various cancers. MIC-1 regulates various cancer hallmarks, including sustained proliferation, tumor-promoting inflammation, avoiding immune destruction, inducing invasion, metastasis, angiogenesis, and resisting cell death. Despite these facts, the molecular regulation and downstream signaling of MIC-1 in cancer remain elusive, partly because its receptor (GFRAL) was unknown until recently. Binding of MIC-1 to GFRAL recruits the coreceptor tyrosine kinase RET to execute its downstream signaling. So far, studies have shown that GFRAL expression is restricted to the brain stem and is responsible for MIC-1/GFRAL/RET-mediated metabolic disorders. Nevertheless, abundant levels of MIC-1 expression have been reported in all cancer types and have been proposed as a surrogate biomarker. Given the ubiquitous expression of MIC-1 in cancers, it is crucial to understand both upstream regulation and downstream MIC-1/GFRAL/RET signaling in cancer hallmark traits.

Genetically modified immunomodulatory cell-based biomaterials in tissue regeneration and engineering

To date, the wide application of cell-based biomaterials in tissue engineering and regeneration is remarkably hampered by immune rejection. Reducing the immunogenicity of cell-based biomaterials has become the latest direction in biomaterial research. Recently, genetically modified cell-based biomaterials with immunomodulatory genes have become a feasible solution to the immunogenicity problem. In this review, recent advances and future challenges of genetically modified immunomodulatory cell-based biomaterials are elaborated, including fabrication approaches, mechanisms of common immunomodulatory genes, application and, more importantly, current preclinical and clinical advances. The fabrication approaches can be categorized into commonly used (e.g., virus transfection) and newly developed approaches. The immunomodulatory mechanisms of representative genes involve complicated cell signaling pathways and metabolic activities. Wide application in curing multiple end-term diseases and replacing lifelong immunosuppressive therapy in multiple cell and organ transplantation models is demonstrated. Most significantly, practices of genetically modified organ transplantation have been conducted on brain-dead human decedent and even on living patients after a series of experiments on nonhuman primates. Nevertheless, uncertain biosecurity, nonspecific effects and overlooked personalization of current genetically modified immunomodulatory cell-based biomaterials are shortcomings that remain to be overcome.

GDF15, an emerging key player in human aging

Growth differentiation factor 15 (GDF15) is recently emerging not only as a stress-related mitokine, but also as a key player in the aging process, being one of the most up-regulated protein with age and associated with a variety of age-related diseases (ARDs). Many data indicate that GDF15 has protective roles in several tissues during different stress and aging, thus playing a beneficial role in apparent contrast with the observed association with many ARDs. A possible detrimental role for this protein is then hypothesized to emerge with age. Therefore, GDF15 can be considered as a pleiotropic factor with beneficial activities that can turn detrimental in old age possibly when it is chronically elevated. In this review, we summarize the current knowledge on the biology of GDF15 during aging. We also propose GDF15 as a part of a dormancy program, where it may play a role as a mediator of defense processes aimed to protect from inflammatory damage and other stresses, according to the life history theory.

Evaluating the adverse outcome of subtypes of heart failure with preserved ejection fraction defined by machine learning: A systematic review focused on defining high risk phenogroups

The ability to distinguish clinically meaningful subtypes of heart failure with preserved ejection fraction (HFpEF) has recently been examined by machine learning techniques but studies appear to have produced discordant results. The objective of this study is to synthesize the types of HFpEF by examining their features and relating them to phenotypes with adverse prognosis. A systematic search was conducted using the search terms "Diastolic Heart Failure" OR "heart failure with preserved ejection fraction" OR "heart failure with normal ejection fraction" OR "HFpEF" AND "machine learning" OR "artificial intelligence" OR 'computational biology'. Ten studies were identified and they varied in their prevalence of ten clinical variables: age, sex, body mass index (BMI) or obesity, hypertension, diabetes mellitus, coronary artery disease, atrial fibrillation, chronic kidney disease, chronic obstructive pulmonary disease or symptom severity (NYHA class or BNP). The clinical findings associated with the different phenotypes in > 85 % of studies were age, hypertension, atrial fibrillation, chronic kidney disease and worse symptoms severity; an adverse outcome was in 65 % to 85 % of studies identified diabetes mellitus and female sex and in less than 65 % of studies was body mass index or obesity, and coronary artery disease. COPD was a relevant factor in only 33 % of studies. Adverse clinical outcome - death or admission to hospital (for heart failure) defined phenogroups with the worst outcome. Combining the 4 studies that calculated the MAGGIC score showed a significant (p<0.05) linear relationship between MAGGIC score and outcome, using the one-year event rate. A new score based on strength of the evidence of the HFpEF studies analyzed here, using 9 variables (eliminating COPD), showed a significant (p<0.009) linear relationship with one-year event rate. Three studies examined biomarkers in detail and the ones most prominently related to outcome or consistently found in the studies were GDF15, FABP4, FGF23, sST2, renin and TNF. The dominant factors that identified phenotypes of HFpEF with adverse outcome were hypertension, atrial fibrillation, chronic kidney disease and worse symptoms severity. A new simplified score, based on clinical factors, was proposed to assess prognosis in HFpEF. Several biomarkers were consistently elevated in phenogroups with adverse outcomes and may indicate the underlying mechanism or pathophysiology specific for phenotypes with an adverse prognosis.

A growth factor-expressing macrophage subpopulation orchestrates regenerative inflammation via GDF-15

Muscle regeneration is the result of the concerted action of multiple cell types driven by the temporarily controlled phenotype switches of infiltrating monocyte-derived macrophages. Pro-inflammatory macrophages transition into a phenotype that drives tissue repair through the production of effectors such as growth factors. This orchestrated sequence of regenerative inflammatory events, which we termed regeneration-promoting program (RPP), is essential for proper repair. However, it is not well understood how specialized repair-macrophage identity develops in the RPP at the transcriptional level and how induced macrophage-derived factors coordinate tissue repair. Gene expression kinetics-based clustering of blood circulating Ly6Chigh, infiltrating inflammatory Ly6Chigh, and reparative Ly6Clow macrophages, isolated from injured muscle, identified the TGF-β superfamily member, GDF-15, as a component of the RPP. Myeloid GDF-15 is required for proper muscle regeneration following acute sterile injury, as revealed by gain- and loss-of-function studies. Mechanistically, GDF-15 acts both on proliferating myoblasts and on muscle-infiltrating myeloid cells. Epigenomic analyses of upstream regulators of Gdf15 expression identified that it is under the control of nuclear receptors RXR/PPARγ. Finally, immune single-cell RNA-seq profiling revealed that Gdf15 is coexpressed with other known muscle regeneration-associated growth factors, and their expression is limited to a unique subpopulation of repair-type macrophages (growth factor-expressing macrophages [GFEMs]).

Chrono-communication and cardiometabolic health: The intrinsic relationship and therapeutic nutritional promises

Circadian rhythm, an innate 24-h biological clock, regulates several mammalian physiological activities anticipating daily environmental variations and optimizing available energetic resources. The circadian machinery is a complex neuronal and endocrinological network primarily organized into a central clock, suprachiasmatic nucleus (SCN), and peripheral clocks. Several small molecules generate daily circadian fluctuations ensuring inter-organ communication and coordination between external stimuli, i.e., light, food, and exercise, and body metabolism. As an orchestra, this complex network can be out of tone. Circadian disruption is often associated with obesity development and, above all, with diabetes and cardiovascular disease onset. Moreover, accumulating data highlight a bidirectional relationship between circadian misalignment and cardiometabolic disease severity. Food intake abnormalities, especially timing and composition of meal, are crucial cause of circadian disruption, but evidence from preclinical and clinical studies has shown that food could represent a unique therapeutic approach to promote circadian resynchronization. In this review, we briefly summarize the structure of circadian system and discuss the role playing by different molecules [from leptin to ghrelin, incretins, fibroblast growth factor 21 (FGF-21), growth differentiation factor 15 (GDF15)] to guarantee circadian homeostasis. Based on the recent data, we discuss the innovative nutritional interventions aimed at circadian re-synchronization and, consequently, improvement of cardiometabolic health.

The impact of cichorium intybus L. On GDF-15 level in obese diabetic albino mice as compared with metformin effect

BACKGROUND

Diabetes mellitus (DM) and obesity comorbidity signify a frequent metabolic disorder, representing a huge public health burden. Metformin, the most used anti-diabetic medication, is found to reduce body weight via growth differentiation factor 15 (GDF-15) signalling pathways. The medicinal herb Cichorium intybus L. (chicory or cichorium) has a promising pharmacological impact on energy homeostasis. On the other hands, little data is available on its role in DM and obesity. Despite its irrefutable effect, its exact mechanism of action has not completely elucidated; the present study evaluated the effect of chicory on DM, antioxidant status, inflammation, and GDF-15 level in comparison with the metformin effect.

MATERIAL AND METHODS

Eighty albino mice were grouped as (control, obese diabetic group, metformin-treated, and Cichorium intybus L. -treated group). The study assessed blood glucose, lipid profile, inflammatory markers (IL-6, TNF-α), total antioxidant capacity (TAC) and caspase-3. Quantitative RT-PCR assessed GDF-15 and leptin relative mRNA expression.

RESULTS

Cichorium intybus L. has significantly lowered inflammatory, apoptotic markers, and leptin levels compared with the diseased group. Likewise, the plant upregulated GDF-15 and TAC's levels. The study documented a non-significant difference between the Cichorium intybus L. -treated and the metformin-treated groups in all estimated markers.

CONCLUSION

The Cichorium intybus L. is a promising herbal supplement with anti-inflammatory, antioxidant, anti-diabetic, and weight reduction effects via affecting GDF-15 signalling pathways.

GRAPHICAL ABSTRACT

GDF-15 has anti-inflammatory, anti-oxidative stress and anti-apoptotic effect in DM and obesity via targeting NF-κB mechanisms.

The Role of GDF15 as a Myomitokine

Growth differentiation factor 15 (GDF15) is a cytokine best known for affecting systemic energy metabolism through its anorectic action. GDF15 expression and secretion from various organs and tissues is induced in different physiological and pathophysiological states, often linked to mitochondrial stress, leading to highly variable circulating GDF15 levels. In skeletal muscle and the heart, the basal expression of GDF15 is very low compared to other organs, but GDF15 expression and secretion can be induced in various stress conditions, such as intense exercise and acute myocardial infarction, respectively. GDF15 is thus considered as a myokine and cardiokine. GFRAL, the exclusive receptor for GDF15, is expressed in hindbrain neurons and activation of the GDF15–GFRAL pathway is linked to an increased sympathetic outflow and possibly an activation of the hypothalamic-pituitary-adrenal (HPA) stress axis. There is also evidence for peripheral, direct effects of GDF15 on adipose tissue lipolysis and possible autocrine cardiac effects. Metabolic and behavioral outcomes of GDF15 signaling can be beneficial or detrimental, likely depending on the magnitude and duration of the GDF15 signal. This is especially apparent for GDF15 production in muscle, which can be induced both by exercise and by muscle disease states such as sarcopenia and mitochondrial myopathy.

GDF15: emerging biology and therapeutic applications for obesity and cardiometabolic disease

Growth differentiation factor 15 (GDF15) is a member of the TGFβ superfamily whose expression is increased in response to cellular stress and disease as well as by metformin. Elevations in GDF15 reduce food intake and body mass in animal models through binding to glial cell-derived neurotrophic factor family receptor alpha-like (GFRAL) and the recruitment of the receptor tyrosine kinase RET in the hindbrain. This effect is largely independent of other appetite-regulating hormones (for example, leptin, ghrelin or glucagon-like peptide 1). Consistent with an important role for the GDF15-GFRAL signalling axis, some human genetic studies support an interrelationship with human obesity. Furthermore, findings in both mice and humans have shown that metformin and exercise increase circulating levels of GDF15. GDF15 might also exert anti-inflammatory effects through mechanisms that are not fully understood. These unique and distinct mechanisms for suppressing food intake and inflammation makes GDF15 an appealing candidate to treat many metabolic diseases, including obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease, cardiovascular disease and cancer cachexia. Here, we review the mechanisms regulating GDF15 production and secretion, GDF15 signalling in different cell types, and how GDF15-targeted pharmaceutical approaches might be effective in the treatment of metabolic diseases.

Circular RNA Foxo3 in cardiac ischemia-reperfusion injury in heart transplantation: A new regulator and target

Ischemia-reperfusion (I/R) injury occurring in heart transplantation (HT) remains as a leading cause of transplant heart graft failure. Circular RNAs (circRNAs) play important roles in gene regulation and diseases. However, the impact of circRNAs on I/R injury during HT remains unknown. This study aims to investigate the role of circular RNA Foxo3 (circFoxo3) in I/R injury in HT. Using an in vivo mouse HT model and an in vitro cardiomyocyte culture model, we demonstrated that circFoxo3 is significantly upregulated in I/R-injured hearts and hypoxia/reoxygenation (H/R)-damaged cardiomyocytes. Knockdown of circFoxo3 using siRNA not only reduces cell apoptosis and death, mitochondrial damage, and expression of apoptosis/death-related genes in vitro, but also protects heart grafts from prolonged cold I/R injury in HT. We also show that circFoxo3 interacts with Foxo3 proteins and inhibits the phosphorylation of Foxo3 and that it indirectly affects the expression of miR-433 and miR-136. In conclusion, circRNA is involved in I/R injury in HT and knockdown of circFoxo3 with siRNA can reduce I/R injury and improve heart graft function through interaction with Foxo3. This study highlights that circRNA is a new type of molecular regulator and a potential target for preventing I/R injury in HT.

GDF15 and Cardiac Cells: Current Concepts and New Insights

Growth and differentiation factor 15 (GDF15) belongs to the transforming growth factor-β (TGF-β) superfamily of proteins. Glial-derived neurotrophic factor (GDNF) family receptor α-like (GFRAL) is an endogenous receptor for GDF15 detected selectively in the brain. GDF15 is not normally expressed in the tissue but is prominently induced by “injury”. Serum levels of GDF15 are also increased by aging and in response to cellular stress and mitochondrial dysfunction. It acts as an inflammatory marker and plays a role in the pathogenesis of cardiovascular diseases, metabolic disorders, and neurodegenerative processes. Identified as a new heart-derived endocrine hormone that regulates body growth, GDF15 has a local cardioprotective role, presumably due to its autocrine/paracrine properties: antioxidative, anti-inflammatory, antiapoptotic. GDF15 expression is highly induced in cardiomyocytes after ischemia/reperfusion and in the heart within hours after myocardial infarction (MI). Recent studies show associations between GDF15, inflammation, and cardiac fibrosis during heart failure and MI. However, the reason for this increase in GDF15 production has not been clearly identified. Experimental and clinical studies support the potential use of GDF15 as a novel therapeutic target (1) by modulating metabolic activity and (2) promoting an adaptive angiogenesis and cardiac regenerative process during cardiovascular diseases. In this review, we comment on new aspects of the biology of GDF15 as a cardiac hormone and show that GDF15 may be a predictive biomarker of adverse cardiac events.

Preventing alloimmune rejection using circular RNA FSCN1-silenced dendritic cells in heart transplantation

BACKGROUND

While heart transplantation is used as a standard treatment for heart failure, transplant rejection continues to pose a challenge. Recent evidence has shown that circular RNA (circRNA) is a new type of gene regulator in cell development. Our aim was to demonstrate that treatment with tolerogenic dendritic cells (Tol-DCs) generated by circular RNA FSCN1 (circFSCN1) silencing could prevent alloimmune rejection and prolong heart graft survival in heart transplantation.

METHODS

Bone marrow-derived DCs were transfected with circFSCN1 siRNA in vitro. The circFSCN1 level was measured by qRT-PCR. DC maturation was determined by flow cytometry. Mixed lymphocyte reactions (MLRs) were conducted to assess the function of DCs to activate T cells and to generate regulatory T cells (Tregs). In situ RNA hybridization and fluorescent microscopy were performed to detect the distribution of circFSCN1 in DCs. A heterotopic allogeneic murine heart transplantation was conducted where recipients were pre-treated with donor derived circFSCN1-silenced Tol-DCs. Heartbeat was monitored to assess immune rejection.

RESULTS

Exonic circFSCN1 was highly expressed in the cytoplasm of mature DCs. Knockdown of circFSCN1 using siRNA arrested DCs at an immature state, impaired DC's ability to activate T cells and enhanced Treg generation. Treatment with circFSCN1-silenced Tol-DCs prevented alloimmune rejection, prolonged allograft survival, reduced fibrosis, and induced Tregs in vivo.

CONCLUSIONS

Knockdown of circFSCN1 induces Tol-DCs and treatment with these Tol-DCs prevents alloimmune rejection and prolongs allograft survival. This is a promising therapeutic target to combat transplant rejection in heart transplantation and increases our understanding of circRNA in the immune system.

An Addition of U0126 Protecting Heart Grafts From Prolonged Cold Ischemia-Reperfusion Injury in Heart Transplantation: A New Preservation Strategy

BACKGROUND

Ischemia-reperfusion injury (IRI) is the major cause of primary graft dysfunction in organ transplantation. The mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) signaling pathway plays a crucial role in cell physiological and pathological processes including IRI. This study aims to investigate whether inhibition of ERK signaling with U0126 can prevent prolonged cold IRI in heart transplantation.

METHODS

Rat cardiac cell line H9c2 cells were treated with U0126 before exposure to hypothermic hypoxia/reoxygenation (H/R) conditions. The effect of U0126 on H9c2 cells in response to H/R stress was determined by measuring cell death, reactive oxygen species production, mitochondrial membrane potential, and ERK signaling activation. Mouse syngeneic heterotopic heart transplantation was conducted, where a donor heart was preserved in the University of Wisconsin (UW) solution supplemented with U0126 for 24 hours at 4°C before transplantation. Heart graft function, histopathologic changes, apoptosis, and fibrosis were measured to assess IRI.

RESULTS

Phosphorylated ERK was increased in both in vitro H/R-injured H9c2 cells and in vivo heart grafts with IRI. Pretreatment with U0126 inhibited ERK phosphorylation and prevented H9c2 cells from cell death, reactive oxygen species generation, and mitochondrial membrane potential loss in response to H/R. Preservation of donor hearts with U0126-supplemented solution improved graft function and reduced IRI by reductions in cell apoptosis/death, neutrophil infiltration, and fibrosis of the graft.

CONCLUSIONS

Addition of U0126 to UW solution reduces ERK signal activation and attenuates prolonged cold IRI in a heart transplantation model. ERK inhibition with U0126 may be a useful strategy to minimize IRI in organ transplantation.

Insights Into Mechanisms of GDF15 and Receptor GFRAL: Therapeutic Targets

Growth and differentiation factor 15 (GDF15) belongs to the transforming growth factor-β (TGF-β) superfamily proteins. GDF15 acts as an inflammatory marker, and it plays a role in pathogenesis of tumors, ischemic diseases, metabolic disorders, and neurodegenerative processes. GDF15 is not normally expressed in the tissue; it is prominently induced following 'injury'. GDF15 functions are critical for the regulation of endothelial adaptations after vascular damage. Recently, four research groups simultaneously identified glial-derived neurotrophic factor (GDNF)-family receptor α-like (GFRAL) in the brain, an orphan receptor as the receptor for GDF15, signaling through the coreceptor RET. In this article, new aspects of the biology of GDF15 and receptor GFRAL, and their relationship with various pathologies, are commented on.

GDF15, an update of the physiological and pathological roles it plays: a review

Growth differentiation factor 15 (GDF15) is a peptide hormone, and a divergent member of the transforming growth factor beta (TGFβ) superfamily. In normal physiology, GDF15 is expressed in multiple tissues at a low concentration. GDF15 is overexpressed during and following many pathological conditions such as tissue injury and inflammation in order to play a protective role. However, GDF15 appears to promote tumour growth in the later stages of malignant cancer. The recently identified endogenous receptor for GDF15, GDNF family receptor a-like (GFRAL), has allowed elucidation of a physiological pathway in which GDF15 regulates energy homeostasis and body weight, primarily via appetite suppression. The anorectic effect of GDF15 provides some therapeutic potential in management of cancer-related anorexia/cachexia and obesity. Despite the identification of GFRAL as a GDF15 receptor, there appears to be other signalling mechanisms utilized by GDF15 that further increase the possibility of development of therapeutic treatments, should these pathways be fully characterized. In this review, GDF15 function in both physiological and pathological conditions in various tissues will be discussed.

β-catenin regulates myocardial ischemia/reperfusion injury following heterotopic heart transplantation in mice by modulating PTEN pathways

Ischemia reperfusion (I/R) injury, an inevitable event accompanying heart transplantation, is the primary factor leading to organ failure and graft rejection. In order to prevent I/R injury, we established murine heart transplantation model with I/R and cell culture system to determine whether β-catenin is a mediate factor in preventing I/R injury in heart transplantation. After successfully established heterotopic heart transplantation mice model, the I/R injury was induced, and two dynamic temporal were studied during different I/R phases. With the increase of ischemia and reperfusion time, heart damage was more severe. In the initial study, we observed that β-catenin was significantly decreased, while ROCK1 and PTEN increased during the perfusion phase from day 0 to day 1, and remain the same level until 3 days later. The similar pattern that β-catenin was down-regulated while ROCK1 and PTEN were up-regulated was also observed in the dynamic temporal ischemia study. To further investigate the role of β-catenin signaling in I/R injury in vitro, β-catenin over-expressing plasmid was transfected into HL-1 cells, a cardiac cell line. We noted that β-catenin over-expressing cardiomyocytes showed decreased ROCK1/PTEN expression both at mRNA and protein levels. In addition, cobalt dichloride (CoCl₂) -induced oxidative stress model was further established to mimic cardiac I/R injury. We observed that CoCl₂-induced activation of ROCK1/PTEN signaling pathway were attenuated by transient transfection of a β-catenin over-expressing plasmid. Taken together, our results suggest that cardiac transplant induced IR injury is closely associated with the down-regulation of β-catenin and up-regulation of ROCK1 and PTEN expression.

Manipulating Cellular Energetics to Slow Aging of Tissues and Organs

Up to now numerous studies in the field of gerontology have been published. Nevertheless, a well-known food restriction remains the most reliable and efficient way of lifespan extension. Physical activity is also a well-documented anti-aging intervention being especially efficient in slowing down the age-associated decline of skeletal muscle mass. In this review we focus on the molecular mechanisms of the effect of physical exercise on muscle tissues. We also discuss the possibilities of pharmacological extension of this effect to the rest of the tissues. During the exercise, the level of ATP decreases triggering activation of AMP-dependent protein kinase (AMPK). This kinase stimulates antioxidant potential of the cells and their mitochondrial respiratory capacity. The exercise also induces mild oxidative stress, which, in turn, mediates the stimulation via hormetic response. Furthermore, during the exercise cells generate activators of mammalian target of rapamycin (mTOR). The intracellular ATP level increases during the rest periods between exercises thus promoting mTOR activation. Therefore, regular exercise intermittently activates anti-oxidant defenses and mitochondrial biogenesis (via AMPK and the hormetic response) of the muscle tissue, as well as its proliferative potential (via mTOR), which, in turn, impedes the age-dependent muscle atrophy. Thus, the intermittent treatment with activators of (i) AMPK combined with the inducers of hormetic response and of (ii) mTOR might partly mimic the effects of physical exercise. Importantly, pharmacological activation of AMPK takes place in the absence of ATP level decrease. The use of uncouplers of respiration and oxidative phosphorylation at the phase of AMPK activation could also prevent negative consequences of the cellular hyper-energization. It is believed that the decline of both antioxidant and proliferative potentials of the cells causes the age-dependent decline of multiple tissues, rather than only the muscular one. We argue that the approach above is applicable for the majority of tissues in an organism.

Serum GDF15, a Promising Biomarker in Obese Patients Undergoing Heart Surgery

Background: Obesity is a risk factor that negatively impacts outcomes in patients undergoing heart surgery by mechanisms that are not well-defined nor predicated on BMI alone. This knowledge gap has fuelled a search for biomarkers associated with cardiovascular diseases that could provide clinical insight to surgeons. One such biomarker is growth differentiation factor15(GDF15), associated with inflammation, metabolism, and heart failure outcomes but not yet examined in the context of obesity and cardiac surgery outcomes.

Methods: Patients undergoing open-heart surgery were consented and enrolled for blood and tissue (atria) sampling at the time of surgery. Biomarker analysis was carried out using ELISA and western blot/qPCR, respectively. Biomarker screening was classified by inflammation(NLR, GDF15, Galectin3, ST2, TNFR2), heart failure(HF)/remodeling(NT-proBNP) and metabolism(glycemia, lipid profile). Patients were categorized based on BMI: obese group (BMI ≥30.0) and non-obese group(BMI 20.0–29.9). Subsequent stratification of GDF15 high patients was conservatively set as being in the 75th percentile.

Results: A total of 80 patients undergoing any open-heart surgical interventions were included in the study. Obese (mean BMI = 35.8, n = 38) and non-obese (mean BMI = 25.7, n = 42) groups had no significant differences in age, sex, or co-morbidities. Compared to other biomarkers, plasma GDF15 (mean 1,736 vs. 1,207 ng/l, p < 0.001) was significantly higher in obese patients compared to non-obese. Plasma GDF15 also displayed a significant linear correlation with BMI (R² = 0.097; p = 0.0049). Atria tissue was shown to be a significant source of GDF15 protein and tissue levels significantly correlated with plasma GDF15 (R² = 0.4, p = 0.0004). Obesity was not associated with early/late mortality at median follow-up >2years. However, patients with high GDF15 (>1,580 ng/l) had reduced survival (65%) compared to the remaining patients with lower GDF15 levels (95%) by Kaplan Meier Analysis (median >2 years; p = 0.007).

Conclusions: Circulating GDF15 is a salient biomarker likely sourced from heart tissue that appears to predict higher risk obese patients for adverse outcomes. More importantly, elevated GDF15 accounted for more sensitive outcome association than BMI at 2 years post-cardiac surgery, suggesting it heralds links to pathogenicity and should be actively studied prospectively and dynamically in a post-operative follow-up.

Trial number: NCT03248921.

The utility of growth differentiation factor-15, galectin-3, and sST2 as biomarkers for the diagnosis of heart failure with preserved ejection fraction and compared to heart failure with reduced ejection fraction: a systematic review

The objective was to evaluate the diagnosis of heart failure with preserved ejection fraction (HFpEF) using the biomarkers, growth differentiation factor-15 (GDF-15), galectin-3 (Gal-3), and soluble ST2 (sST2), and to determine whether they can differentiate HFpEF from heart failure with reduced ejection fraction (HFrEF). Medline and Embase databases were searched with the terms diastolic heart failure or HFpEF, biomarkers, and diagnosis, limited to years 2000 to 2019. There were significantly and consistently higher levels of GDF-15, Gal-3, and sST2 in HFpEF compared to no heart failure. Importantly, the magnitude of the increase in GDF-15 or Gal-3 and possibly sST2,correlated with a greater degree of diastolic dysfunction. There were no significant differences between GDF-15, Gal-3, and sST2 in patients with HFpEF vs HFrEF. In the studies assessing these three biomarkers, BNP was significantly greater in heart failure than controls. Furthermore, BNP was significantly higher in HFrEF compared to HFpEF. The diagnostic utility of GDF-15, Gal-3, and sST2 compared to BNP was evaluated by comparing ROC curves. The data supports the contention that to distinguish HFpEF from HFrEF, an index is needed that incorporates GDF-15, Gal-3, or sST2 as well as BNP. The three biomarkers GDF-15, Gal-3, or sST2 can identify patients with HFpEF compared to individuals without heart failure but cannot differentiate HFpEF from HFrEF. BNP is higher in and is better at differentiating HFrEF from HFpEF. Indices that incorporate GDF-15, Gal-3, or sST2 as well as BNP show promise in differentiating HFpEF from HFrEF.

Increased concentrations of growth differentiation factor-15 in children with Kawasaki disease

BACKGROUND

We investigated the serum concentrations of growth differentiation factor-15 (GDF-15) in children with acute Kawasaki disease (KD) and evaluate its role in predicting coronary artery lesions (CALs) and no response KD.

METHODS

We obtained blood sample from 30 healthy children and 131 children with KD before intravenous immunoglobulin therapy. Serum GDF-15 concentrations were measured using ELISA kits. Univariate and multivariate logistic regression analysis were conducted to evaluate the potential association between GDF-15 and the occurrence of CALs and treatment responses.

RESULTS

Serum GDF-15 concentrations in KD were remarkably increased compared with healthy control. Serum GDF-15 concentrations in KD with CALs were also increased compared with no CALs, and in no response KD compared with response KD. Serum of GDF-15 concentrations was positively correlated with white blood cell count, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), and negatively associated with albumin and pre-albumin in all patients with KD. GDF-15 was an independent predictor of CALs and no response KD. GDF-15 was superior to CRP and ESR, while it was not inferior to the combination of CRP and ESR for predicting CALs.

CONCLUSIONS

Serum of GDF-15 concentrations was significantly increased in acute KD patients, especially in KD with CALs and no response KD. GDF-15 could sever as an independent predictor for CALs and no response KD.

Functional roles of GDF15 in modulating microenvironment to promote carcinogenesis

Obesity and related metabolic dysregulation are risk factors for many types of cancer. The interactions between a developing tumor and its microenvironment are known to implicate a complex "crosstalk" among the factors produced by the population of cells. Among these factors, Growth and differentiation factor 15 (GDF15) has a functional role in cancer. GDF15 expression is induced in response to the conditions associated with cellular stress and diseases. The GDF15 receptor, a member of the glial-cell-derived neurotropic factor family (GDNF), is a GDNF family receptor α-like (GFRAL) protein. GDF15 induces pro-angiogenic effects in tumors. However, GDF15 could affect tumorigenesis both positively and negatively. With a better understanding of the upstream disease pathways reflected by GDF15, new treatment targets may emerge.

Supplementing preservation solution with mitochondria-targeted H2 S donor AP39 protects cardiac grafts from prolonged cold ischemia-reperfusion injury in heart transplantation

Heart transplant has been accepted as the standard treatment for end-stage heart failure. Because of its susceptibility to ischemia-reperfusion injury, the heart can be preserved for only 4 to 6 hours in cold static preservation solutions. Prolonged ischemia time is adversely associated with primary graft function and long-term survival. New strategies to preserve donor hearts are urgently needed. We demonstrate that AP39, a mitochondria-targeting hydrogen sulfide donor, significantly increases cardiomyocyte viability and reduces cell apoptosis/death after cold hypoxia/reoxygenation in vitro. It also decreases gene expression of proinflammatory cytokines and preserves mitochondria function. Using an in vivo murine heart transplant model, we show that preserving donor hearts with AP39-supplemented University of Wisconsin solution (n = 7) significantly protects heart graft function, measured by quantitative ultrasound scan, against prolonged cold ischemia-reperfusion injury (24 hours at 4°C), along with reducing tissue injury and fibrosis. Our study demonstrates that supplementing preservation solution with AP39 protects cardiac grafts from prolonged ischemia, highlighting its therapeutic potential in preventing ischemia-reperfusion injury in heart transplant.

GDF15 secreted by senescent endothelial cells improves vascular progenitor cell functions

Endothelial dysfunction (ED) is part of the first steps in the development of cardiovascular diseases (CVD). Growth Differentiation Factor 15 (GDF15) is a cytokine belonging to the Transforming Growth Factor β superfamily and its expression is increased both during ED and in CVD. Because high blood levels of GDF15 have been reported during ED, we hypothesized that GDF15 could be produced by endothelial cells in response to a vascular stress, possibly to attenuate endothelial function loss. Since senescence is mainly involved in both vascular stress and endothelial function loss, we used Endothelial Colony Forming Cells generated from adult blood (AB-ECFCs) as a model of endothelial cells to investigate GDF15 expression during cellular senescence. Then, we analyzed the potential role of GDF15 in AB-ECFC functions and senescence. When AB-ECFCs become senescent, they secrete increased levels of GDF15. We investigated GDF15 paracrine effects on non-senescent AB-ECFCs and showed that GDF15 enhanced proliferation, migration, NO production and activated several signaling pathways including AKT, ERK1/2 and SMAD2 without triggering any oxidative stress. Taken together, our results suggest that GDF15 production by senescent AB-ECFCs could act in a paracrine manner on non-senescent AB-ECFCs, and that this interaction could be beneficial to its model cells. Therefore, GDF15 could play a beneficial role in a dysfunctional vascular system as previously reported in patients with CVD, by limiting ED related to vascular stress occurring in these diseases.

Growth differentiation factor 15 (GDF15): A survival protein with therapeutic potential in metabolic diseases

Growth Differentiation Factor 15 (GDF15), also known as NSAID activated gene-1 (NAG-1), is associated with a large number of biological processes and diseases, including cancer and obesity. GDF15 is synthesized as pro-GDF15, is dimerized, and is cleaved and secreted into the circulation as a mature dimer GDF15. Both the intracellular GDF15 and the circulating mature GDF15 are implicated in biological processes, such as energy homeostasis and body weight regulation. Although there have been many studies on GDF15, GFRAL, a member of the glial-derived neurotropic factor receptor α family, has only been recently identified as a receptor for mature GDF15. In this review, we focused on cancer and energy homeostasis along with obesity and body weight, and the effect of the identification of the GDF15 receptor in these investigations. In addition, the therapeutic potential of GDF15 as a pharmacological agent in obesity and other metabolic diseases was discussed.

GDF15 Regulates Malat-1 Circular RNA and Inactivates NFκB Signaling Leading to Immune Tolerogenic DCs for Preventing Alloimmune Rejection in Heart Transplantation

Recombinant human growth differentiation factor 15 (rhGDF15) affects dendritic cell (DC) maturation. However, whether GDF15 is expressed in DCs and its roles and signaling in DCs remain largely unknown. It is unclear whether GDF15-DCs can induce immune tolerance in heart transplantation (HT). This study aims to understand the impact of endogenous GDF15 on DC's development, function, underlying molecular mechanism including circular RNA (circRNA). This study will also explore GDF15-DC-mediated immune modulation in HT. Bone marrow (BM) derived DCs were cultured and treated to up- or down regulate GDF15 expression. Phenotype and function of DCs were detected. Expression of genes and circRNAs was determined by qRT-PCR. The signaling pathways activated by GDF15 were examined. The impact of GDF15 treated DCs on preventing allograft immune rejection was assessed in a MHC full mismatch mouse HT model. Our results showed that GDF15 was expressed in DCs. Knockout of GDF15 promoted DC maturation, enhanced immune responsive functions, up-regulated malat-1 circular RNA (circ_Malat 1), and activated the nuclear factor kappa B (NFκB) pathway. Overexpression of GDF15 in DCs increased immunosuppressive/inhibitory molecules, enhanced DCs to induce T cell exhaustion, and promoted Treg generation through IDO signaling. GDF15 utilized transforming growth factor (TGF) β receptors I and II, not GFAL. Administration of GDF15 treated DCs prevented allograft rejection and induced immune tolerance in transplantation. In conclusion, GDF15 induces tolerogenic DCs (Tol-DCs) through inhibition of circ_Malat-1 and the NFκB signaling pathway and up-regulation of IDO. GDF15-DCs can prevent alloimmune rejection in HT.

Mitochondrial transplantation prolongs cold ischemia time in murine heart transplantation

BACKGROUND

Cold ischemia time (CIT) causes ischemia‒reperfusion injury to the mitochondria and detrimentally effects myocardial function and tissue viability. Mitochondrial transplantation replaces damaged mitochondria and enhances myocardial function and tissue viability. Herein we investigated the efficacy of mitochondrial transplantation in enhancing graft function and viability after prolonged CIT.

METHODS

Heterotopic heart transplantation was performed in C57BL/6J mice. Upon heart harvesting from C57BL/6J donors, 0.5 ml of either mitochondria (1 × 10⁸ in respiration buffer; mitochondria group) or respiration buffer (vehicle group) was delivered antegrade to the coronary arteries via injection to the coronary ostium. The hearts were excised and preserved for 29 ± 0.3 hours in cold saline (4°C). The hearts were then heterotopically transplanted. A second injection of either mitochondria (1 × 10⁸) or respiration buffer (vehicle) was delivered antegrade to the coronary arteries 5 minutes after transplantation. Grafts were analyzed for 24 hours. Beating score, graft function, and tissue injury were measured.

RESULTS

Beating score, calculated ejection fraction, and shortening fraction were significantly enhanced (p < 0.05), whereas necrosis and neutrophil infiltration were significantly decreased (p < 0.05) in the mitochondria group as compared with the vehicle group at 24 hours of reperfusion. Transmission electron microscopy showed the presence of contraction bands in vehicle but not in mitochondria grafts.

CONCLUSIONS

Mitochondrial transplantation prolongs CIT to 29 hours in the murine heart transplantation model, significantly enhances graft function, and decreases graft tissue injury. Mitochondrial transplantation may provide a means to reduce graft failure and improve transplantation outcomes after prolonged CIT.

The MIC-1/GDF15-GFRAL Pathway in Energy Homeostasis: Implications for Obesity, Cachexia, and Other Associated Diseases

MIC-1/GDF15 is a stress response cytokine and a distant member of the transforming growth factor beta (TGFb) superfamily, with no close relatives. It acts via a recently identified receptor called glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL), which is a distant orphan member of the GDNF receptor family that signals through the tyrosine kinase receptor Ret. MIC-1/GDF15 expression and serum levels rise in response to many stimuli that initiate cell stress and as part of a wide variety of disease processes, most prominently cancer and cardiovascular disease. The best documented actions of MIC-1/GDF15 are on regulation of energy homeostasis. When MIC-1/GDF15 serum levels are substantially elevated in diseases like cancer, it subverts a physiological pathway of appetite regulation to induce an anorexia/cachexia syndrome initiated by its actions on hindbrain neurons. These effects make it a potential target for the treatment of both obesity and anorexia/cachexia syndromes, disorders lacking any highly effective, readily accessible therapies.

Hsp27 reduces cold ischemia-reperfusion injury in heart transplantation through regulation of NF-κB and PUMA signaling

BACKGROUND AND OBJECTIVE

Global myocardial ischemia-reperfusion (I/R) injury after heart transplantation is believed to impair graft function and aggravate episodes of both acute and chronic rejection. The 27-kDa heat shock protein (Hsp27) has a potent ability to alleviate I/R after cardiac transplantation. The aim of this study was to investigate the anti-I/R injury effect of Hsp27 to elucidate the underling mechanisms.

METHODS

Heart grafts from BALB/c mice were preserved in University of Wisconsin (UW) solution (control) or UW solution containing pAAV-Hsp27 (Hsp27 solution) at 4°C for 48 h and subsequently transplanted into syngeneic recipients for 72 h. The heart grafts were then collected for histopathological and gene expression analyses. An in vitro I/R model (H9c2 cells or H9c2/Hsp27 cells) was constructed. Then, protein and mRNA expression of Hsp27, p65, p53 upregulated modulator of apoptosis (PUMA), interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α in heart tissues and H9c2 cells were detected with western blot and reverse transcription polymerase chain reaction analyses. Caspase-3 activity was detected using a commercial assay, while protein levels of IL-6, IL-1β, and TNF-α were detected using specific enzyme-linked immunosorbent assays. NF-κB activity was detected with an electrophoretic mobility shift assay. Cell apoptosis was detected with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and flow cytometric analysis.

RESULTS

Cold I/R caused severe morphologic myocardial injury of heart grafts from wild type C57BL/c mice, whereas grafts from Hsp27 preservation showed less damage as demonstrated by decreased cell apoptosis/death and the preservation of the normal structure of the heart. Hsp27 inhibited I/R-induced injury as indicated by the reduction in cardiac troponin I activities and decreased cardiac tissue levels of the proinflammatory factors TNF-α, IL-1β, and IL-6. Hsp27 was further demonstrated to significantly inhibit nuclear translocation of p65 and p53 upregulated modulator of apoptosis (PUMA) expression.

CONCLUSIONS

These results suggested that the cardioprotective effect of Hsp27 could be due to the suppression of the myocardial inflammatory response and apoptosis by blocking the NF-κB-dependent pro-inflammatory and NF-κB-dependent PUMA signaling pathways.