Depletion of T lymphocytes ameliorates cardiac fibrosis in streptozotocin-induced diabetic cardiomyopathy
Introduction
Myocardial fibrosis, one of the cardinal features of diabetic cardiomyopathy, contributes to increased ventricular stiffness which is accountable for contractile dysfunction in failing diabetic hearts [1], [2]. Much progress on the cellular and molecular mechanisms of cardiac fibrosis has been achieved. Immune cells, cardiomyocytes, and endothelial cells have been proposed to contribute to the formation of fibrotic process by secreting pro-fibrotic mediators to modulate differentiation of fibroblasts to myofibroblasts [3]. Some neurohumoral factors, cytokines, and reactive oxygen species are recognized to play distinct but overlapping roles in the pathogenesis of fibrosis [4]. However, the underlying mechanism of fibrosis remains controversial.
Several patient-based studies have shown increased expansion of proinflammatory T cell subsets in diabetic patient blood that is correlated with adverse cardiac events including acute coronary syndrome [5], [6]. A recent study on murine pressure-overload-induced heart failure has shown that T lymphocyte presence in injured cardiac tissue is associated with exacerbated fibrosis [7]. T lymphocytes can activate profibrotic cells and are involved in fibrosis perpetuation by secreting proinflammatory cytokines [8]. T cells infiltration in diabetic myocardium has been observed [9]. Although results in different approaches including neutralizing antibodies or genetic knockout of signaling protein of T cells have shown reduced fibrosis in murine heart failure models, T cell-based therapeutic interventions to protect hearts against diabetic injury need to be explored. Modulation of T cell trafficking and its effect on long term diabetic fibrogenesis are still not known clearly. Further, crosstalk between T cells and other cellular components in myocardial fibrosis has not been addressed. Fibrocytes, blood derived monocyte-lineage cells that secrete increased extracellular matrix protein under chronic injury/inflammation or with appropriate external stimuli, e.g. transforming growth factor beta 1 (TGF-β1), can differentiate fibroblasts into myofibroblasts [10], [11].
Sphingosine 1-phosphate (S1P), a small bioactive lipid molecule, plays pivotal roles in many physiological processes, such as: cell migration, angiogenesis, cytoskeleton reorganization, and survival, by activating G protein-coupled S1P receptors or intracellular targets [12]. Clinical and experimental data have shown that circulating S1P is predictive for obstructive coronary artery disease and type 1 diabetes [13], [14]. S1P and S1P receptor 1 (S1P1) signaling have been implicated in inflammation-mediated myocardial injury [15]. Mature lymphocytes upregulate the expression of S1P1 for their egress from lymphoid organs to circulation [16]. FTY720 down-modulates lymphocytic S1P1 receptor, thus induces lymphopenia by sequestering them in secondary lymphoid organs [17]. FTY720 protects cardiac microvascular structure and function in diabetic rats [18], [19]. However, the role of T cells in FTY720-induced cardioprotection against diabetic injury was unknown.
We hypothesized that modulation of T cell trafficking through S1P1 functional antagonism could protect the heart from diabetes-associated fibrosis and cardiac dysfunction. In the present study, we investigated T cell trafficking modulation by using fingolimod (FTY720), an immunomodulatory drug, and recombination activating genes 1 (Rag1) knock-out mice without mature lymphocytes as a genetic approach in streptozotocin-induced type 1 diabetic cardiomyopathy model by quantifying T lymphocytes in the heart and circulation, identification of CD34-bearing fibrocyte localization in cardiac tissue, profibrotic TGF-β1 expression, S1P1 expression, heart histological study, fibrosis area measurement in heart sections, and ex vivo cardiac function evaluation.
Section snippets
Animals
This investigation was carried out in accordance with the Guide for the Care and Use of Laboratory Animals set forth by U.S. National Research Council (8th Edition, 2011). All experimental procedures involving mice in this study were approved by the Institutional Animal Care and Use Committee at South Dakota State University. Eight-week old male wild-type (WT) C57BL/6 mice were purchased from the Charles River Laboratories (Wilmington, MA, USA) and two breeding pairs of Rag1 knockout (KO) mice
Assessment of metabolic and physiological parameters under diabetes
In the present study, we used multiple low doses of STZ to induce type 1 diabetes in mice. Body weight, blood glucose levels and serum insulin levels were measured and analyzed in all groups of both WT and KO mice (Fig. 1). In WT mice, both untreated (STZ, n = 9) and FTY720-treated (FTY720 + STZ, n = 9) diabetic mice demonstrated lower body weight gain trend compared with only buffer treatment (Control, n = 8) mice throughout 11 weeks (Fig. 1B). At the end, control group gained 10% higher body weight
Discussion
The major findings of the present study indicate that chronic administration of FTY720 treatment induces sustained reduction of T lymphocytes in circulation with reduced CD3 T cell infiltration into heart tissue under hyperglycemic condition and exerts cardioprotection and anti-fibrosis in WT diabetic mice. Cardiac protection and anti-fibrosis are also observed in diabetic Rag1 KO mice without mature lymphocytes. Remarkably, FTY720 causes heart injury in diabetic Rag1 KO mice.
FTY720, a
Disclosures
No conflicts of interest, financial or otherwise are declared by the authors.
Acknowledgements
This project was supported by the Department of Pharmaceutical Sciences, College of Pharmacy, South Dakota State University and the Department of Pharmaceutical & Biomedical Sciences, College of Pharmacy, California Northstate University (Z. Jin).
References (34)
- et al.
Diabetes-associated cardiac fibrosis: cellular effectors, molecular mechanisms and therapeutic opportunities
J. Mol. Cell. Cardiol.
(2016) Immunological aspect of cardiac remodeling: T lymphocyte subsets in inflammation-mediated cardiac fibrosis
Exp. Mol. Pathol.
(2011)- et al.
Monocytic fibroblast precursors mediate fibrosis in angiotensin-II-induced cardiac hypertrophy
J. Mol. Cell. Cardiol.
(2010) - et al.
Predicting obstructive coronary artery disease with serum sphingosine-1-phosphate
Am. Heart J.
(2003) - et al.
Circulating sphingolipid biomarkers in models of type 1 diabetes
J. Lipid Res.
(2011) - et al.
The immune modulator FTY720 targets sphingosine 1-phosphate receptors
J. Biol. Chem.
(2002) - et al.
Simultaneous determination of sphingosine and sphingosine 1-phosphate in biological samples by liquid chromatography-tandem mass spectrometry
J. Chromatogr. B Analyt. Technol. Biomed. Life Sci.
(2011) - et al.
Sphingosine kinase type 2 is essential for lymphopenia induced by the immunomodulatory drug FTY720
Blood
(2006) Sphingosine 1-phopshate receptors in health and disease: mechanistic insights from gene deletion studies and reverse pharmacology
Pharmacol. Ther.
(2007)- et al.
Immunomodulator FTY720 induces myofibroblast differentiation via lysophospholipid receptor S1P3 and Smad3 signaling
Am. J. Pathol.
(2007)
Diastolic stiffness of the failing diabetic heart: importance of fibrosis, advanced glycation end products, and myocyte resting tension
Circulation
Diabetes and cardiovascular disease: a statement for healthcare professionals from the American Heart Association
Circulation
Molecular mechanisms of diabetic cardiomyopathy
Diabetologia
Expansion of CD4+ CD28null T-lymphocytes in diabetic patients: exploring new pathogenetic mechanisms of increased cardiovascular risk in diabetes mellitus
Eur. Heart J.
Increased peripheral proinflammatory T helper subsets contribute to cardiovascular complications in diabetic patients
Mediat. Inflamm.
Left ventricular T cell recruitment contributes to the pathogenesis of heart failure
Circ. Heart Fail.
Assessment of cardiac inflammation and remodeling during the development of streptozotocin-induced diabetic cardiomyopathy in vivo: a time course analysis
Int. J. Mol. Med.
Cited by (34)
Cellular mechanisms and recommended drug-based therapeutic options in diabetic cardiomyopathy
2021, Pharmacology and TherapeuticsCitation Excerpt :There are first animal studies available that emphasize the S1P axis as a possible target for improvement of DM CM. Functional antagonism of the S1P receptors by fingolimod treatment reduced fibrotic changes in DM mice (Abdullah, Li, Wang, & Jin, 2016). Moreover, fingolimod medication was shown to prevent the incidence of DM in rats (Kobayashi et al., 2020).
Backstage players of fibrosis: NOX4, mTOR, HDAC, and S1P; companions of TGF-β
2021, Cellular SignallingCitation Excerpt :Moreover, transgenic mice with overexpression of S1PR1 develop cardiac hypertrophy with increased expressions of the fibrotic markers α-SMA and collagen enriched in fibroblasts [292]. As occur in other organs, the use of the S1PR antagonist FTY720 reduces fibrotic lesions in cardiac fibrosis in rodents, induced by heart transplantation [293], diabetic cardiomyopathy [294], transverse aortic constriction [295], and also in an I/R model by aortic occlusion followed by reperfusion in pigs [296]. The more specific relation with the fibrotic process was reported for S1PR3, whose its genetic deletion reduces cardiac fibrosis development and decreases SMAD3 phosphorylation in a model of I/R [297].
Fibrosis of the diabetic heart: Clinical significance, molecular mechanisms, and therapeutic opportunities
2021, Advanced Drug Delivery ReviewsCitation Excerpt :Limited information is available on the potential role of T cells in diabetic cardiac fibrosis. Genetic depletion of circulating CD4 + and CD8 + lymphocytes in a type 1 diabetes model attenuated cardiac fibrosis [180,181,182]. Whether these effects were specific to myocardial complications of diabetes, or reflected broad effects of lymphocyte targeting on diabetic complications remains unknown.
Adding insult to injury - Inflammation at the heart of cardiac fibrosis
2021, Cellular SignallingRegulatory T cells in ischemic cardiovascular injury and repair
2019, Journal of Molecular and Cellular CardiologyCitation Excerpt :In myocarditis, recent studies revealed the protective effect of Tregs against myocarditis by downregulating cardiac proinflammatory cytokine, modulating monocyte/macrophage presence [117], and reducing the virus copy number, while others reported that Tregs may contribute to viral persistence and infection by prematurely limiting the antiviral immune response in myocarditis [118,119]. Additionally, although one study found that depletion of T cells ameliorates cardiac fibrosis in streptozotocin-induced diabetic cardiomyopathy [120], there is no study directly revealing the role of Tregs in diabetic hearts. As Tregs can suppress Teffs responses by various pathways in Type 2 diabetes and Tregs play an important role in ischemic cardiac injury, clarification of the role of Tregs in the diabetic heart injury will be informative.
Heart Inflammation: Immune Cell Roles and Roads to the Heart
2019, American Journal of PathologyCitation Excerpt :The current understanding of the complex immune response in the different etiologies of HF is reviewed in this section (Figure 1). Table 1 summarizes the immune cells that are recruited during heart inflammation and the main molecules involved in the process.11–74 Several pathogens infect a variety of cardiac cells and induce the acute immune response and inflammation necessary for pathogen killing.
- 1
Current address: Center for Cardiovascular Diseases and Sciences, Department of Pathology, Louisiana State University Health Science Center, Shreveport, LA 71103, USA.
- 2
Current address: Divison of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA.