Epigallocatechin-3-Gallate Attenuates Myocardial Dysfunction via Inhibition of Endothelial-to-Mesenchymal Transition.

Cardiac tissue damage following ischemia leads to cardiomyocyte apoptosis and myocardial fibrosis. Epigallocatechin-3-gallate (EGCG), an active polyphenol flavonoid or catechin, exerts bioactivity in tissues with various diseases and protects ischemic myocardium; however, its association with the endothelial-to-mesenchymal transition (EndMT) is unknown. Human umbilical vein endothelial cells (HUVECs) pretreated with transforming growth factor ß2 (TGF-ß2) and interleukin 1ß (IL-1ß) were treated with EGCG to verify cellular function. In addition, EGCG is involved in RhoA GTPase transmission, resulting in reduced cell mobility, oxidative stress, and inflammation-related factors. A mouse myocardial infarction (MI) model was used to confirm the association between EGCG and EndMT in vivo. In the EGCG-treated group, ischemic tissue was regenerated by regulating proteins involved in the EndMT process, and cardioprotection was induced by positively regulating apoptosis and fibrosis of cardiomyocytes. Furthermore, EGCG can reactivate myocardial function due to EndMT inhibition. In summary, our findings confirm that EGCG is an impact activator controlling the cardiac EndMT process derived from ischemic conditions and suggest that supplementation with EGCG may be beneficial in the prevention of cardiovascular disease.

Emerging role of anti-proliferative protein BTG1 and BTG2.

The B cell translocation gene 1 (BTG1) and BTG2 play a key role in a wide range of cellular activities including proliferation, apoptosis, and cell growth via modulating a variety of central biological steps such as transcription, post-transcriptional, and translation. BTG1 and BTG2 have been identified by genomic profiling of B-cell leukemia and diverse lymphoma types where both genes are commonly mutated, implying that they serve as tumor suppressors. Furthermore, a low expression level of BTG1 or BTG2 in solid tumors is frequently associated with malignant progression and poor treatment outcomes. As physiological aspects, BTG1 and BTG2 have been discovered to play a critical function in regulating quiescence in hematopoietic lineage such as Hematopoietic stem cells (HSCs) and naïve and memory T cells, highlighting their novel role in maintaining the quiescent state. Taken together, emerging evidence from the recent studies suggests that BTG1 and BTG2 play a central anti-proliferative role in various tissues and cells, indicating their potential as targets for innovative therapeutics. [BMB Reports 2022; 55(8): 380-388].

mRNA destabilization by BTG1 and BTG2 maintains T cell quiescence.

T cells maintain a quiescent state prior to activation. As inappropriate T cell activation can cause disease, T cell quiescence must be preserved. Despite its importance, the mechanisms underlying the "quiescent state" remain elusive. Here, we identify BTG1 and BTG2 (BTG1/2) as factors responsible for T cell quiescence. BTG1/2-deficient T cells show an increased proliferation and spontaneous activation due to a global increase in messenger RNA (mRNA) abundance, which reduces the threshold to activation. BTG1/2 deficiency leads to an increase in polyadenylate tail length, resulting in a greater mRNA half-life. Thus, BTG1/2 promote the deadenylation and degradation of mRNA to secure T cell quiescence. Our study reveals a key mechanism underlying T cell quiescence and suggests that low mRNA abundance is a crucial feature for maintaining quiescence.

Homeobox protein Hhex negatively regulates Treg cells by inhibiting Foxp3 expression and function.

Regulatory T (Treg) cells play an essential role in maintaining immune homeostasis, but the suppressive function of Treg cells can be an obstacle in the treatment of cancer and chronic infectious diseases. Here, we identified the homeobox protein Hhex as a negative regulator of Treg cells. The expression of Hhex was lower in Treg cells than in conventional T (Tconv) cells. Hhex expression was repressed in Treg cells by TGF-ß/Smad3 signaling. Retroviral overexpression of Hhex inhibited the differentiation of induced Treg (iTreg) cells and the stability of thymic Treg (tTreg) cells by significantly reducing Foxp3 expression. Moreover, Hhex-overexpressing Treg cells lost their immunosuppressive activity and failed to prevent colitis in a mouse model of inflammatory bowel disease (IBD). Hhex expression was increased; however, Foxp3 expression was decreased in Treg cells in a delayed-type hypersensitivity (DTH) reaction, a type I immune reaction. Hhex directly bound to the promoters of Foxp3 and other Treg signature genes, including Il2ra and Ctla4, and repressed their transactivation. The homeodomain and N-terminal repression domain of Hhex were critical for inhibiting Foxp3 and other Treg signature genes. Thus, Hhex plays an essential role in inhibiting Treg cell differentiation and function via inhibition of Foxp3.

YinYang1 deficiency ameliorates joint inflammation in a murine model of rheumatoid arthritis by modulating Th17 cell activation.

Yin Yang 1 (YY1) is a ubiquitously expressed transcription factor that functions in cooperation with various cofactors to regulate gene expression. In the immune system, YY1 enhances cytokine production and T helper (Th) 2 effector cell differentiation, resulting in the activation of inflammation. However, no studies have reported the role of YY1 in Th17 cell regulation, which is implicated in rheumatoid arthritis (RA). We investigated the expression of YY1 in Th17 cells in vitro and revealed increased levels of YY1 mRNA and protein. To elucidate the function of YY1 pathogenesis in RA, we used a collagen-induced arthritis (CIA) mouse model with YY1 deficiency. Deficiency of YY1 reduced the severity of arthritis and joint destruction. Moreover, Th17 cells were dramatically reduced in YY1-deficient mice. The cytokine interleukin (IL)-17 was decreased in YY1-deficient CD4+ T cells ex vivo and in vivo. Interestingly, the level of signal transducer and activator of transcription 3 (STAT3), tumor necrosis factor-α, IL-17, IL-6, and IL-1ß were markedly decreased in YY1-deficient mice with CIA. The cytokine-inducing function of YY1 was more specific to IL-17 than to interferon-γ. YY1 plays a role in Th17 cell differentiation and RA pathogenesis. Our findings suggest that future RA therapies should target the regulatory mechanism involved in Th17 cell differentiation, in which YY1 may cooperate with the STAT3 signaling pathway.

PTEN drives Th17 cell differentiation by preventing IL-2 production.

T helper 17 (Th17) cells are a CD4+ T cell subset that produces IL-17A to mediate inflammation and autoimmunity. IL-2 inhibits Th17 cell differentiation. However, the mechanism by which IL-2 is suppressed during Th17 cell differentiation remains unclear. Here, we show that phosphatase and tensin homologue (PTEN) is a key factor that regulates Th17 cell differentiation by suppressing IL-2 production. Th17-specific Pten deletion (Ptenfl/flIl17acre ) impairs Th17 cell differentiation in vitro and ameliorated symptoms of experimental autoimmune encephalomyelitis (EAE), a model of Th17-mediated autoimmune disease. Mechanistically, Pten deficiency up-regulates IL-2 and phosphorylation of STAT5, but reduces STAT3 phosphorylation, thereby inhibiting Th17 cell differentiation. PTEN inhibitors block Th17 cell differentiation in vitro and in the EAE model. Thus, PTEN plays a key role in Th17 cell differentiation by blocking IL-2 expression.

Casein kinase 2 is a critical determinant of the balance of Th17 and Treg cell differentiation.

Th17 cells promote inflammatory reactions, whereas regulatory T (Treg) cells inhibit them. Thus, the Th17/Treg cell balance is critically important in inflammatory diseases. However, the molecular mechanisms underlying this balance are unclear. Here, we demonstrate that casein kinase 2 (CK2) is a critical determinant of the Th17/Treg cell balance. Both the inhibition of CK2 with a specific pharmacological inhibitor, CX-4945, and its small hairpin RNA (shRNA)-mediated knockdown suppressed Th17 cell differentiation but reciprocally induced Treg cell differentiation in vitro. Moreover, CX-4945 ameliorated the symptoms of experimental autoimmune encephalomyelitis and reduced Th17 cell infiltration into the central nervous system. Mechanistically, CX-4945 inhibited the IL-6/STAT3 and Akt/mTOR signaling pathways. Thus, CK2 has a crucial role in regulating the Th17/Treg balance.

D-dopachrome tautomerase in adipose tissue inflammation and wound repair.

D-dopachrome tautomerase (D-DT/MIF-2) is a member of the macrophage migration inhibitory factor (MIF) cytokine superfamily, and a close structural homolog of MIF. MIF and D-DT have been reported to be involved in obesity, but there is little known about the regulation of D-DT in adipose tissue inflammation and wound healing. Subcutaneous adipose tissue was collected from 54 healthy donors and 28 donors with acutely inflamed wounds undergoing wound debridement. In addition, epididymal fat pads of mice were injected with lipopolysaccharide to study receptor expression and cell migration in vivo. D-DT protein levels and mRNA expression were significantly decreased in subcutaneous adipose tissue adjacent to acutely inflamed wounds. D-DT improved fibroblast viability and increased proliferation in vitro. While D-DT alone did not have a significant effect on in vitro fibroblast wound healing, simultaneous addition of neutralizing MIF antibody resulted in a significant improvement of fibroblast wound healing. Interestingly, expression of the MIF and D-DT receptor CD74 was down-regulated while the MIF receptors CXCR2 and CXCR4 were up-regulated primarily on macrophages indicating that the MIF-CXCR2/4 axis may promote recruitment of inflammatory cells into adipose tissue. Our results describe a reciprocal role of D-DT to MIF in inflamed adipose tissue, and indicate that D-DT may be beneficial in wound repair by improving fibroblast survival and proliferation.

Loss of the SUMO protease Ulp2 triggers a specific multichromosome aneuploidy.

Post-translational protein modification by the small ubiquitin-related modifier (SUMO) regulates numerous cellular pathways, including transcription, cell division, and genome maintenance. The SUMO protease Ulp2 modulates many of these SUMO-dependent processes in budding yeast. From whole-genome RNA sequencing (RNA-seq), we unexpectedly discovered that cells lacking Ulp2 display a twofold increase in transcript levels across two particular chromosomes: chromosome I (ChrI) and ChrXII. This is due to the two chromosomes being present at twice their normal copy number. An abnormal number of chromosomes, termed aneuploidy, is usually deleterious. However, development of specific aneuploidies allows rapid adaptation to cellular stresses, and aneuploidy characterizes most human tumors. Extra copies of ChrI and ChrXII appear quickly following loss of active Ulp2 and can be eliminated following reintroduction of ULP2, suggesting that aneuploidy is a reversible adaptive mechanism to counteract loss of the SUMO protease. Importantly, increased dosage of two genes on ChrI-CLN3 and CCR4, encoding a G1-phase cyclin and a subunit of the Ccr4-Not deadenylase complex, respectively-suppresses ulp2Δ aneuploidy, suggesting that increased levels of these genes underlie the aneuploidy induced by Ulp2 loss. Our results reveal a complex aneuploidy mechanism that adapts cells to loss of the SUMO protease Ulp2.

The Effect of Lipoaspirates on Human Keratinocytes.

BACKGROUND: One increasingly important trend in plastic, reconstructive, and aesthetic surgery is the use of fat grafts to improve cutaneous wound healing. In clinical practice, lipoaspirates (adipose tissue harvested by liposuction) are re-injected in a procedure called lipofilling. Previous studies, however, mainly evaluated the regenerative effect of isolated adipocytes, adipose-derived stem cells, and excised en bloc adipose tissue on keratinocytes, whereas no study to date has examined the effect of lipoaspirates. OBJECTIVES: The authors aimed to investigate differences in the regenerative property of en bloc adipose tissue and lipoaspirates on keratinocytes. METHODS: Human keratinocytes, lipoaspirates, and en bloc adipose tissue from 36 healthy donors were isolated. In vitro proliferation, differentiation, migration, stratification, and wound healing of keratinocyte monolayers were measured. Furthermore, secreted levels of VEGF, bFGF, IGF-1, MMP-9, and MIF were detected by ELISA. RESULTS: Migration, proliferation, and wound healing of keratinocytes were increased by lipoaspirates. Interestingly, the effect of lipoaspirates on keratinocyte proliferation was significantly higher than by en bloc adipose tissue after 5 days. The differentiation of keratinocytes was equally attenuated by lipoaspirates and en bloc adipose tissue. Stratification of keratinocyte layers was enhanced by lipoaspirates and en bloc fat when compared to controls. Lipoaspirates secrete higher levels of bFGF, whereas higher levels of VEGF and IGF-1 are released by en bloc adipose tissue. CONCLUSION: We show that lipoaspirates and en bloc adipose tissue have a regenerative effect on keratinocytes. One reason for the higher effect of lipoaspirates on keratinocyte proliferation may be the secretion of different cytokines.

PPARγ negatively regulates T cell activation to prevent follicular helper T cells and germinal center formation.

Peroxisome proliferator-activated receptor gamma (PPARγ) is a transcription factor that regulates lipid and glucose metabolism. Although studies of PPARγ ligands have demonstrated its regulatory functions in inflammation and adaptive immunity, its intrinsic role in T cells and autoimmunity has yet to be fully elucidated. Here we used CD4-PPARγKO mice to investigate PPARγ-deficient T cells, which were hyper-reactive to produce higher levels of cytokines and exhibited greater proliferation than wild type T cells with increased ERK and AKT phosphorylation. Diminished expression of IκBα, Sirt1, and Foxo1, which are inhibitors of NF-κB, was observed in PPARγ-deficient T cells that were prone to produce all the signature cytokines under Th1, Th2, Th17, and Th9 skewing condition. Interestingly, 1-year-old CD4-PPARγKO mice spontaneously developed moderate autoimmune phenotype by increased activated T cells, follicular helper T cells (TFH cells) and germinal center B cells with glomerular inflammation and enhanced autoantibody production. Sheep red blood cell immunization more induced TFH cells and germinal centers in CD4-PPARγKO mice and the T cells showed increased of Bcl-6 and IL-21 expression suggesting its regulatory role in germinal center reaction. Collectively, these results suggest that PPARγ has a regulatory role for TFH cells and germinal center reaction to prevent autoimmunity.

GATA-binding protein-3 regulates T helper type 2 cytokine and ifng loci through interaction with metastasis-associated protein 2.

GATA-binding protein-3 (GATA-3) regulates the T helper type 2 (Th2) cytokine locus through induction of chromatin remodelling. However, the molecular mechanism for this is poorly understood. To understand this mechanism better, we screened GATA-3 interacting proteins using affinity purification and mass spectrometry. We found that GATA-3 bound to metastasis-associated protein 2 (MTA-2), a component of the NuRD chromatin remodelling complex. GATA-3 and MTA-2 in turn bound to several regulatory regions of the Th2 cytokine locus and the ifng promoter. Cell transfection assay showed that MTA-2 acted as an antagonist with GATA-3 in the expression of Th2 cytokines, but co-operated with GATA-3 in the repression of the ifng gene expression. These results suggest that GATA-3 interacts with MTA-2 to co-ordinately regulate Th2 cytokine and ifng loci during T helper cell differentiation.

HHQ and PQS, two Pseudomonas aeruginosa quorum-sensing molecules, down-regulate the innate immune responses through the nuclear factor-kappaB pathway.

To explore whether bacterial secreted 4-hydroxy-2-alkylquinolines (HAQs) can regulate host innate immune responses, we used the extracts of bacterial culture supernatants from a wild-type (PA14) and two mutants of Pseudomonas aeruginosa that have defects in making HAQs. Surprisingly, the extract of supernatants from the P. aeruginosa pqsA mutant that does not make HAQs showed strong stimulating activity for the production of innate cytokines such as tumour necrosis factor-alpha and interleukin-6 in the J774A.1 mouse monocyte/macrophage cell line, whereas the extract from the wild-type did not. The addition of 4-hydroxy-2-heptylquinoline (HHQ) or 2-heptyl-3,4-dihydroxyquinoline (PQS, Pseudomonas quinolone signal) to mammalian cell culture media abolished this stimulating activity of the extracts of supernatants from the pqsA mutant on the expression of innate cytokines in J774A.1 cells and in the primary bronchoalveolar lavage cells from C57BL/6 mice, suggesting that HHQ and PQS can suppress the host innate immune responses. The pqsA mutant showed reduced dissemination in the lung tissue compared with the wild-type strain in a mouse in vivo intranasal infection model, suggesting that HHQ and PQS may play a role in the pathogenicity of P. aeruginosa. HHQ and PQS reduced the nuclear factor-kappaB (NF-kappaB) binding to its binding sites and the expression of NF-kappaB target genes, and PQS delayed inhibitor of kappaB degradation, indicating that the effect of HHQ and PQS was mediated through the NF-kappaB pathway. Our results suggest that HHQ and PQS produced by P. aeruginosa actively suppress host innate immune responses.