TNNI3K is a novel mediator of myofilament function and phosphorylates cardiac troponin I

Embryonic Hyperglycemia Disrupts Myocardial Growth, Morphological Development, and Cellular Organization: An In Vivo Experimental Study

Hyperglycemia during gestation can disrupt fetal heart development and increase postnatal cardiovascular disease risk. It is therefore imperative to identify early biomarkers of hyperglycemia during gestation-induced fetal heart damage and elucidate the underlying molecular pathomechanisms. Clinical investigations of diabetic adults with heart dysfunction and transgenic mouse studies have revealed that overexpression or increased expression of TNNI3K, a heart-specific kinase that binds troponin cardiac I, may contribute to abnormal cardiac remodeling, ventricular hypertrophy, and heart failure. Optimal heart function also depends on the precise organization of contractile and excitable tissues conferred by intercellular occlusive, adherent, and communicating junctions. The current study evaluated changes in embryonic heart development and the expression levels of sarcomeric proteins (troponin I, desmin, and TNNI3K), junctional proteins, glucose transporter-1, and Ki-67 under fetal hyperglycemia. Stage 22HH Gallus domesticus embryos were randomly divided into two groups: a hyperglycemia (HG) group, in which individual embryos were injected with 30 mmol/L glucose solution every 24 h for 10 days, and a no-treatment (NT) control group, in which individual embryos were injected with physiological saline every 24 h for 10 days (stage 36HH). Embryonic blood glucose, height, and weight, as well as heart size, were measured periodically during treatment, followed by histopathological analysis and estimation of sarcomeric and junctional protein expression by western blotting and immunostaining. Hyperglycemic embryos demonstrated delayed heart maturation, with histopathological analysis revealing reduced left and right ventricular wall thickness (−39% and −35% vs. NT). Immunoexpression levels of TNNI3K and troponin 1 increased (by 37% and 39%, respectively), and desmin immunofluorescence reduced (by 23%). Embryo-fetal hyperglycemia may trigger an increase in the expression levels of TNNI3K and troponin I, as well as dysfunction of occlusive and adherent junctions, ultimately inducing abnormal cardiac remodeling.

Cardiac Troponin I-Interacting Kinase Affects Cardiomyocyte S-Phase Activity but Not Cardiomyocyte Proliferation

BACKGROUND

Identifying genetic variants that affect the level of cell cycle reentry and establishing the degree of cell cycle progression in those variants could help guide development of therapeutic interventions aimed at effecting cardiac regeneration. We observed that C57Bl6/NCR (B6N) mice have a marked increase in cardiomyocyte S-phase activity after permanent coronary artery ligation compared with infarcted DBA/2J (D2J) mice.

METHODS

Cardiomyocyte cell cycle activity after infarction was monitored in D2J, (D2J×B6N)-F1, and (D2J×B6N)-F1×D2J backcross mice by means of bromodeoxyuridine or 5-ethynyl-2'-deoxyuridine incorporation using a nuclear-localized transgenic reporter to identify cardiomyocyte nuclei. Genome-wide quantitative trait locus analysis, fine scale genetic mapping, whole exome sequencing, and RNA sequencing analyses of the backcross mice were performed to identify the gene responsible for the elevated cardiomyocyte S-phase phenotype.

RESULTS

(D2J×B6N)-F1 mice exhibited a 14-fold increase in cardiomyocyte S-phase activity in ventricular regions remote from infarct scar compared with D2J mice (0.798±0.09% versus 0.056±0.004%; P<0.001). Quantitative trait locus analysis of (D2J×B6N)-F1×D2J backcross mice revealed that the gene responsible for differential S-phase activity was located on the distal arm of chromosome 3 (logarithm of the odds score=6.38; P<0.001). Additional genetic and molecular analyses identified 3 potential candidates. Of these, Tnni3k (troponin I-interacting kinase) is expressed in B6N hearts but not in D2J hearts. Transgenic expression of TNNI3K in a D2J genetic background results in elevated cardiomyocyte S-phase activity after injury. Cardiomyocyte S-phase activity in both Tnni3k-expressing and Tnni3k-nonexpressing mice results in the formation of polyploid nuclei.

CONCLUSIONS

These data indicate that Tnni3k expression increases the level of cardiomyocyte S-phase activity after injury.

Knockout of Cardiac Troponin I-Interacting Kinase leads to cardiac dysfunction and remodeling

Cardiac troponin I-interacting kinase (TNNI3K) is a cardiac-specific kinase that has been identified as a diagnostic marker and a therapeutic target in cardiovascular diseases. However, the biological function of TNNI3K in cardiac dysfunction and remodeling remain elusive. In the present study, a Tnni3k cardiomyocyte-specific knockout (Tnni3k-cKO) mouse model was established. Echocardiography was used to evaluate cardiac function in mice. Heart failure markers were detected using enzyme-linked immunosorbent assay. Hematoxylin and eosin staining, wheat germ agglutinin staining, Masson's trichrome staining, Sirius red staining, and TUNEL staining were used to assess histopathological changes, cardiac hypertrophy, collagen deposition, and myocardial apoptosis, respectively. Expression levels of TNNI3K, apoptosis-related proteins, and p38 mitogen-activated protein kinase were measured using Western blot analysis. Compared to wild-type controls, cardiac dysfunction and cardiac remodeling of Tnni3k-cKO mice increased gradually with age. Tnni3k-cKO mice exhibited cardiac hypertrophy, cardiac fibrosis, and cardiomyocyte apoptosis. Upregulation of cleaved caspase-3 in Tnni3k-cKO mice appeared to be related to phosphorylation and activation of the p38 mitogen-activated protein kinase signaling pathway. In conclusion, this study shows that TNNI3K is essential for cardiac development and function, providing new insights into the development of novel therapeutic strategies for cardiac diseases.

Gene losses may contribute to subterranean adaptations in naked mole-rat and blind mole-rat

Background

Naked mole-rats (Heterocephalus glaber, NMRs) and blind mole-rats (Spalax galili, BMRs) are representative subterranean rodents that have evolved many extraordinary traits, including hypoxia tolerance, longevity, and cancer resistance. Although multiple candidate loci responsible for these traits have been uncovered by genomic studies, many of them are limited to functional changes to amino acid sequence and little is known about the contributions of other genetic events. To address this issue, we focused on gene losses (unitary pseudogenes) and systematically analyzed gene losses in NMRs and BMRs, aiming to elucidate the potential roles of pseudogenes in their adaptation to subterranean lifestyle.

Results

We obtained the pseudogene repertoires in NMRs and BMRs, as well as their respective aboveground relatives, guinea pigs and rats, on a genome-wide scale. As a result, 167, 139, 341, and 112 pseudogenes were identified in NMRs, BMRs, guinea pigs, and rats, respectively. Functional enrichment analysis identified 4 shared and 2 species-specific enriched functional groups (EFGs) in subterranean lineages. Notably, the pseudogenes in these EFGs might be associated with either regressive (e.g., visual system) or adaptive (e.g., altered DNA damage response) traits. In addition, several pseudogenes including TNNI3K and PDE5A might be associated with specific cardiac features observed in subterranean lineages. Interestingly, we observed 20 convergent gene losses in NMRs and BMRs. Given that the functional investigations of these genes are generally scarce, we provided functional evidence that independent loss of TRIM17 in NMRs and BMRs might be beneficial for neuronal survival under hypoxia, supporting the positive role of eliminating TRIM17 function in hypoxia adaptation. Our results also suggested that pseudogenes, together with positively selected genes, reinforced subterranean adaptations cooperatively.

Conclusions

Our study provides new insights into the molecular underpinnings of subterranean adaptations and highlights the importance of gene losses in mammalian evolution.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01243-0.

Identification of a nonsense mutation in TNNI3K associated with cardiac conduction disease

BACKGROUND

Cardiac conduction disease (CCD) is a common cardiovascular disease which can lead to life-threatening conditions. The importance of heredity in CCD has been realized in recent years. Several causal genes have been found to be implicated in CCD such as SCN5A, TRPM4, SCN1B, TNNI3K, LMNA, and NKX2.5. To date, only four genetic mutations in TNNI3K have been identified related to CCD.

METHODS

Whole-exome sequencing (WES) was carried out in order to identify the underlying disease-causing mutation in a Chinese family with CCD. The potential mutations were confirmed by Sanger sequencing. Real-time qPCR was used to detect the level of TNNI3K mRNA expression.

RESULTS

A nonsense mutation in TNNI3K (NM_015978.2: g.170891C > T, c.1441C > T) was identified in this family and validated by Sanger sequencing. Real-time qPCR confirmed that the level of TNNI3K mRNA expression was decreased compared with the controls.

CONCLUSIONS

This study found the first nonsense TNNI3K mutation associated with CCD in a Chinese family. TNNI3K harboring the mutation (c.1441C > T) implicated a loss-of-function pathogenic mechanism with an autosomal dominant inheritance pattern. This research enriches the phenotypic spectrum of TNNI3K mutations, casting a new light upon the genotype-phenotype correlations between TNNI3K mutations and CCD and indicating the importance of TNNI3K screening in CCD patients.

Discovery of novel TNNI3K inhibitor suppresses pyroptosis and apoptosis in murine myocardial infarction injury

Myocardial infarction (MI) injury is a highly lethal syndrome that has, until recently, suffered from a lack of clinically efficient targeted therapeutics. The cardiac troponin I interacting kinase (TNNI3K) exacerbates ischemia-reperfusion (IR) injury via oxidative stress, thereby promoting cardiomyocyte death. In this current study, we designed and synthesized 35 novel TNNI3K inhibitors with a pyrido[4,5]thieno[2,3-d] pyrimidine scaffold. In vitro results indicated that some of the inhibitors exhibited sub-micromolar TNNI3K inhibitory capacity and good kinase selectivity, as well as cytoprotective activity, in an oxygen-glucose deprivation (OGD) injury cardiomyocyte model. Furthermore, investigation of the mechanism of the representative derivative compound 6o suggested it suppresses pyroptosis and apoptosis in cardiomyocytes by interfering with p38MAPK activation, which was further confirmed in a murine myocardial infarction injury model. In vivo results indicate that compound 6o can markedly reduce myocardial infarction size and alleviate cardiac tissue damage in rats. In brief, our results provide the basis for further development of novel TNNI3K inhibitors for targeted MI therapy.

3D-QSAR Assisted Design of Novel 7-Deazapurine Derivatives as TNNI3K Kinase Inhibitors Using Molecular Docking and Molecular Dynamics Simulation

Background:

Cardiac troponin I-interacting kinase (TNNI3K) is a cardiac-specific kinase that belongs to MAPKKK family. It is a dual-function kinase with tyrosine and serine/threonine kinase activity. Over-expression of TNNI3K results in various cardiovascular diseases such as cardiomyopathy, ischemia/reperfusion injury, heart failure, etc. Since, it is a cardiac-specific kinase and expressed only in heart tissue, it is an ideal molecular target to treat cardiac diseases. The main objective of the work is to study and understand the structure-activity relationship of the reported deazapurine derivatives and to use the 3D-QSAR and docking results to design potent and novel TNNI3K inhibitors of this series.

Methods:

In the present study, we have used molecular docking 3D QSAR, and molecular dynamics simulation to understand the structure-activity correlation of reported TNNI3K inhibitors and to design novel compounds of deazapurine derivatives with increased activity.

Results:

Both CoMFA (q2=0.669, NOC=5, r2=0.944) and CoMSIA (q2=0.783, NOC=5, r2=0.965) have resulted in satisfactory models. The models were validated using external test set, Leave-out- Five, bootstrapping, progressive scrambling, and rm2 metrics calculations. The validation procedures showed the developed models were robust and reliable. The docking results and the contour maps analysis helped in the better understanding of the structure-activity relationship.

Conclusion:

This is the first report on 3D-QSAR modeling studies of TNNI3K inhibitors. Both docking and MD results were consistent and showed good correlation with the previous experimental data. Based on the information obtained from contour maps, 31 novel TNNI3K inhibitors were designed. These designed compounds showed higher activity than the existing dataset compounds.

Treatment with 20(S)-ginsenoside Rg3 reverses multidrug resistance in A549/DDP xenograft tumors

Multidrug resistance (MDR) is an obstacle for cancer chemotherapy. It was reported that 20(S)-ginsenoside Rg3 (hereafter Rg3) was able to regulate MDR in mouse leukemia cells. The present study investigated the effect of Rg3 on the MDR of A549 lung cancer cells. A cell viability assay revealed that Rg3 treatment increased cisplatin (DDP) cytotoxicity in DDP resistant A549 cells (A549/DDP). Furthermore, Rg3 increases the antitumor effect of DDP on A549/DDP xenograft mice. The expression of MDR-mediated proteins, including P-glycoprotein (P-gp), multidrug resistance-associated protein (MPR1) and lung resistance protein 1 (LPR1), was detected in tumor tissue of A549/DDP xenograft mice. The results revealed that Rg3 treatment inhibited the expression of these MDR-associated proteins. Additionally, technetium-99m labeled hexakis-2-methoxyisobutylisonitrile (^99mTc-MIBI) single-photon emission computed tomography was used to monitor the effect of Rg3 on cisplatin sensitivity of A549/DDP xenograft tumors. It was observed that uptake of ^99mTc-MIBI was increased by Rg3 treatment, which indicated that Rg3 is able to effectively enhance chemotherapy sensitivity of A549/DDP xenograft tumors. Taken together, these results revealed that Rg3 may be able to reverse MDR of lung cancer via the downregulation of P-gp, MPR1 and LPR1.

ACE2, CALM3 and TNNI3K polymorphisms as potential disease modifiers in hypertrophic and dilated cardiomyopathies

The marked clinical and genetic heterogeneity seen in hypertrophic (HCM) and dilated cardiomyopathies (DCM) suggests involvement of disease modifiers and environmental factors in the pathophysiology of these diseases. In the current study, we examined association of single nucleotide polymorphisms (SNPs) of three candidate genes, ACE2 (rs6632677), TNNI3K (rs49812611) and CALM3 (rs13477425) with clinical phenotypes of HCM and DCM patients of North Indian ethnicity. Prevalence of ACE2 (7160726 C>G) variant genotypes (CG and GG) was significantly higher in DCM subjects as compared to controls. Prevalence of TNNI3K (3784 C>T) and CALM3 (-34T>A) variant homozygous genotype were significantly higher in HCM and DCM subjects as compared to controls. DCM patients with CT genotype showed significant decrease in LVEF as compared to CC genotype (p < 0.03). There was significant gene-gene interaction between these SNPs and three-way SNP combination of ACE2 C>G, TNN13K C>T, CALM3 A>T gene variants and was associated with high risk of HCM and DCM. Presence of ACE2 (7160726 C>G) and CALM3 (-34T>A) variant genotypes in HCM Patients with mutations (sarcomeric or non sarcomeric genes) was associated with increased mean septal thickness, further suggesting a role of these gene variants in modifying disease phenotype. Our results suggest that ACE2, TNNI3K and CALM3 polymorphisms are associated with increased risk of HCM and DCM and may act as disease modifiers of these diseases.

Glucagon-like peptide 1 improves insulin resistance in vitro through anti-inflammation of macrophages

Glucagon-like peptide 1 (GLP-1), a kind of gut hormone, is used in the treatment of type 2 diabetes (T2D). Emerging evidence indicates that GLP-1 has anti-inflammatory activity. Chronic inflammation in the adipose tissue of obese individuals is a cause of insulin resistance and T2D. We hypothesized that GLP-1 analogue therapy in patients with T2D could suppress the inflammatory response of macrophages, and therefore inhibit insulin resistance. Our results showed that GLP-1 agonist (exendin-4) not only attenuated macrophage infiltration, but also inhibited the macrophage secretion of inflammatory cytokines including TNF-β, IL-6, and IL-1β. Furthermore, we observed that lipopolysaccharide (LPS)-induced macrophage conditioned media could impair insulin-stimulated glucose uptake. This effect was compensated by treatment with the conditioned media from macrophages treated with the combination of LPS and exendin-4. It was also observed that exendin-4 directly inhibited the activation of NF-κB in macrophages. In conclusion, our results indicated that GLP-1 improved inflammatory macrophage-derived insulin resistance by inhibiting NF-κB pathway and secretion of inflammatory cytokines in macrophages. Furthermore, our observations suggested that the anti-inflammatory effect of GLP-1 on macrophages can contribute to GLP-1 analogue therapy of T2D.

TNNI3K in cardiovascular disease and prospects for therapy

Cardiovascular diseases are an important cause of morbidity and mortality worldwide and the global burden of these diseases continues to grow. Therefore new therapies are urgently needed. The role of protein kinases in disease, including cardiac disease, is long recognized, making kinases important therapeutic targets. We here review the knowledge gathered in the last decade about troponin I-interacting kinase (TNNI3K), a kinase with cardiac-restricted expression that has been implicated in various cardiac phenotypes and diseases including heart failure, cardiomyopathy, ischemia/reperfusion injury and conduction of the cardiac electrical impulse.

Inhibition of the cardiomyocyte-specific troponin I-interacting kinase limits oxidative stress, injury, and adverse remodeling due to ischemic heart disease

Ischemia–reperfusion injury is strongly associated with increased oxidative stress, mitochondrial dysfunction, and cell death. These processes are diminished in an animal model of ischemia–reperfusion by the genetic loss or pharmacological inhibition of troponin I–interacting kinase.