SIRT3-and FAK-mediated acetylation-phosphorylation crosstalk of NFATc1 regulates Nε-carboxymethyl-lysine-induced vascular calcification in diabetes mellitus

BACKGROUND AND AIMS

Arterial calcification is the predictor of cardiovascular risk in diabetic patients. N^ε-carboxymethyl-lysine (CML), a toxic metabolite, is associated with accelerated vascular calcification in diabetes mellitus (DM). However, the mechanism remains elusive. This study aims to explore the key regulators involved in CML-induced vascular calcification in DM.

METHODS

We used Western blot and immuno-staining to test the expression and localization of nuclear factor of activated T cells, cytoplasmic 1 (NFATc1) in human samples, a diabetic apolipoprotein E-deficient (ApoE^-/-) mouse model, and a vascular smooth muscle cells (VSMC) model. Further, we confirmed the regulator of NFATc1 phosphorylation and acetylation induced by CML. The role of NFATc1 in VSMCs calcification and osteogenic differentiation was explored in vivo and in vitro.

RESULTS

In diabetic patients, CML and NFATc1 levels increased in the severe calcified anterior tibial arteries. CML significantly promoted NFATc1 expression and nuclear translocation in VSMCs and mouse aorta. Knockdown of NFATc1 significantly inhibited CML-induced calcification. CML promoted NFATc1 acetylation at K549 by downregulating sirtuin 3 (SIRT3), which antagonized the focal adhesion kinase (FAK) induced NFATc1 phosphorylation at the Y270 site. FAK and SIRT3 affected the nuclear translocation of NFATc1 by regulating the acetylation-phosphorylation crosstalk. NFATc1 dephosphorylation mutant Y270F and deacetylation mutant K549R had opposite effects on VSMC calcification. SIRT3 overexpression and FAK inhibitor could reverse CML-promoted VSMC calcification.

CONCLUSIONS

CML enhances vascular calcification in DM through NFATc1. In this process, CML increases NFATc1 acetylation by downregulating SIRT3 to antagonize FAK-induced NFATc1 phosphorylation.

The Glyoxalase System in Age-Related Diseases: Nutritional Intervention as Anti-Ageing Strategy

The glyoxalase system is critical for the detoxification of advanced glycation end-products (AGEs). AGEs are toxic compounds resulting from the non-enzymatic modification of biomolecules by sugars or their metabolites through a process called glycation. AGEs have adverse effects on many tissues, playing a pathogenic role in the progression of molecular and cellular aging. Due to the age-related decline in different anti-AGE mechanisms, including detoxifying mechanisms and proteolytic capacities, glycated biomolecules are accumulated during normal aging in our body in a tissue-dependent manner. Viewed in this way, anti-AGE detoxifying systems are proposed as therapeutic targets to fight pathological dysfunction associated with AGE accumulation and cytotoxicity. Here, we summarize the current state of knowledge related to the protective mechanisms against glycative stress, with a special emphasis on the glyoxalase system as the primary mechanism for detoxifying the reactive intermediates of glycation. This review focuses on glyoxalase 1 (GLO1), the first enzyme of the glyoxalase system, and the rate-limiting enzyme of this catalytic process. Although GLO1 is ubiquitously expressed, protein levels and activities are regulated in a tissue-dependent manner. We provide a comparative analysis of GLO1 protein in different tissues. Our findings indicate a role for the glyoxalase system in homeostasis in the eye retina, a highly oxygenated tissue with rapid protein turnover. We also describe modulation of the glyoxalase system as a therapeutic target to delay the development of age-related diseases and summarize the literature that describes the current knowledge about nutritional compounds with properties to modulate the glyoxalase system.

Dicarbonyl Stress and S-Glutathionylation in Cerebrovascular Diseases: A Focus on Cerebral Cavernous Malformations

Dicarbonyl stress is a dysfunctional state consisting in the abnormal accumulation of reactive α-oxaldehydes leading to increased protein modification. In cells, post-translational changes can also occur through S-glutathionylation, a highly conserved oxidative post-translational modification consisting of the formation of a mixed disulfide between glutathione and a protein cysteine residue. This review recapitulates the main findings supporting a role for dicarbonyl stress and S-glutathionylation in the pathogenesis of cerebrovascular diseases, with specific emphasis on cerebral cavernous malformations (CCM), a vascular disease of proven genetic origin that may give rise to various clinical signs and symptoms at any age, including recurrent headaches, seizures, focal neurological deficits, and intracerebral hemorrhage. A possible interplay between dicarbonyl stress and S-glutathionylation in CCM is also discussed.

High expression of GLO1 indicates unfavorable clinical outcomes in glioma patients

BACKGROUNDS

Glyoxalase I (GLO1), a ubiquitous enzyme involved in the process of detoxification of methylglyoxal in the cellular glycolysis pathway, was reported to be highly expressed in human tumor. It has also been found that GLO1 is associated with tumor cell survival and proliferation in some types of cancer, such as pancreatic cancer, hepatocellular carcinoma and gastric cancer. However, the role of GLO1 in glioma has not been clarified. The purpose of present study is to explore the expression pattern of GLO1 and whether the expression level of GLO1 is associated with the unfavorable clinical outcomes of patients with glioma.

METHODS

Quantitative RT-PCR and immunohistochemistry staining were used to investigate the mRNA and protein level of GLO1 in glioma tissues together with normal brain tissues. The prognostic role of GLO1 in glioma patients was assessed using univariate and multivariate analyses. Clinical outcomes were estimated by using the Kaplan-Meier analysis and the log-rank test. The function of GLO1 in glioma cell lines were investigated by in vitro experiments.

RESULTS

Expression level of GLO1 was higher in glioma tissues than that in normal brain tissues. High GLO1 expression was significantly correlated with WHO grade and the poor overall survival time in glioma patients. Moreover, GLO1 was also defined as an unfavorable prognosis factor. Overexpression of GLO1 in the glioma cell line U87 can enhance the tumor cell proliferation, migration and invasion. Whereas, knockdown of GLO1 can suppress those abilities.

CONCLUSIONS

Our studies demonstrated that GLO1 was highly expressed in glioma tissues and significantly correlated with the poor prognosis of glioma patients. It indicated that GLO1 might serve as a new prognostic predictor and therapeutic target for glioma treatment.

Reduction of glyoxalase 1 (GLO1) aggravates cerebrovascular remodeling via promoting the proliferation of basilar smooth muscle cells in hypertension

Uncontrollable vascular smooth cell proliferation is responsible for vascular remodeling during hypertension development. Glyoxalase 1 (GLO1), the major enzyme detoxifying methylglyoxal, has a critical role in regulating proliferation of several cell types. However, little is known whether GLO1 is involved in cerebrovascular remodeling and basilar smooth muscle cell (BASMC) proliferation during hypertension. Here we explored the role of GLO1 in angiotensin II (Ang II)-induced cerebrovascular remodeling and proliferation of BASMCs and the underlying mechanisms. The protein expression of GLO1 in basilar arteries from hypertensive mice was decreased, and GLO1 expression was negatively correlated with medial cross-sectional area and blood pressure in basilar arteries during hypertension. Knockdown of GLO1 promoted while overexpression of GLO1 prevented Ang II-induced cell proliferation and cell cycle transition in BASMCs. These results were related to the inhibitory effects of GLO1 on PI3K/AKT/CDK2 cascade activation upon Ang II treatment. In addition, in vivo study, GLO1 overexpression with adeno-associated virus harboring GLO1 cDNA improved cerebrovascular remodeling in basilar artery tissue during Ang II-induced hypertension development. These data indicate that GLO1 reduction mediates cerebrovascular modeling via PI3K/AKT/CDK2 cascade-dependent BASMC proliferation. GLO1 acts as a negative regulator of hypertension-induced cerebrovascular remodeling and targeting GLO1 may be a novel therapeutic strategy to prevent hypertension-associated cardiovascular complications such as stroke.

KRIT1 loss-of-function induces a chronic Nrf2-mediated adaptive homeostasis that sensitizes cells to oxidative stress: Implication for Cerebral Cavernous Malformation disease

KRIT1 (CCM1) is a disease gene responsible for Cerebral Cavernous Malformations (CCM), a major cerebrovascular disease of proven genetic origin affecting 0.3-0.5% of the population. Previously, we demonstrated that KRIT1 loss-of-function is associated with altered redox homeostasis and abnormal activation of the redox-sensitive transcription factor c-Jun, which collectively result in pro-oxidative, pro-inflammatory and pro-angiogenic effects, suggesting a novel pathogenic mechanism for CCM disease and raising the possibility that KRIT1 loss-of-function exerts pleiotropic effects on multiple redox-sensitive mechanisms. To address this possibility, we investigated major redox-sensitive pathways and enzymatic systems that play critical roles in fundamental cytoprotective mechanisms of adaptive responses to oxidative stress, including the master Nrf2 antioxidant defense pathway and its downstream target Glyoxalase 1 (Glo1), a pivotal stress-responsive defense enzyme involved in cellular protection against glycative and oxidative stress through the metabolism of methylglyoxal (MG). This is a potent post-translational protein modifier that may either contribute to increased oxidative molecular damage and cellular susceptibility to apoptosis, or enhance the activity of major apoptosis-protective proteins, including heat shock proteins (Hsps), promoting cell survival. Experimental outcomes showed that KRIT1 loss-of-function induces a redox-sensitive sustained upregulation of Nrf2 and Glo1, and a drop in intracellular levels of MG-modified Hsp70 and Hsp27 proteins, leading to a chronic adaptive redox homeostasis that counteracts intrinsic oxidative stress but increases susceptibility to oxidative DNA damage and apoptosis, sensitizing cells to further oxidative challenges. While supporting and extending the pleiotropic functions of KRIT1, these findings shed new light on the mechanistic relationship between KRIT1 loss-of-function and enhanced cell predisposition to oxidative damage, thus providing valuable new insights into CCM pathogenesis and novel options for the development of preventive and therapeutic strategies.

A Glyoxalase-1 Knockdown Does Not Have Major Short Term Effects on Energy Expenditure and Atherosclerosis in Mice

Objective. Glyoxalase-1 is an enzyme detoxifying methylglyoxal (MG). MG is a potent precursor of advanced glycation endproducts which are regarded to be a key player in micro- and macrovascular damage. Yet, the role of Glo1 in atherosclerosis remains unclear. In this study, the effect of Glo1 on mouse metabolism and atherosclerosis is evaluated. Methods. Glo1 knockdown mice were fed a high fat or a standard diet for 10 weeks. Body weight and composition were investigated by Echo MRI. The PhenoMaster system was used to measure the energy expenditure. To evaluate the impact of Glo1 on atherosclerosis, Glo1(KD) mice were crossed with ApoE-knockout mice and fed a high fat diet for 14 weeks. Results. Glo1 activity was significantly reduced in heart, liver, and kidney lysates derived from Glo1(KD) mice. Yet, there was no increase in methylglyoxal-derived AGEs in all organs analyzed. The Glo1 knockdown did not affect body weight or body composition. Metabolic studies via indirect calorimetry did not show significant effects on energy expenditure. Glo1(KD) mice crossed to ApoE(-/-) mice did not show enhanced formation of atherosclerosis. Conclusion. A Glo1 knockdown does not have major short term effects on the energy expenditure or the formation of atherosclerotic plaques.

Gene expression study in positron emission tomography-positive abdominal aortic aneurysms identifies CCL18 as a potential biomarker for rupture risk

Rupture of abdominal aortic aneurysm (AAA) is a cause of significant mortality and morbidity in aging populations. Uptake of 18-fluorodeoxyglucose (FDG) detected by positron emission tomography (PET) is observed in the wall of 12% of AAA (A+), with most of them being symptomatic. We previously showed that the metabolically active areas displayed adventitial inflammation, medial degeneration and molecular alterations prefacing wall rupture. The aim of this study was to identify new factors predictive of rupture. Transcriptomic analyses were performed in the media and adventitia layers from three types of samples: AAA with-out FDG uptake (A0) and with FDG uptake (A+), both at the positive spot (A+(Pos)) and at a paired distant negative site (A+(Neg)) of the same aneurysm. Follow-up studies included reverse-transcriptase-polymerase chain reaction (RT-PCR), immunohistochemical staining and enzyme-linked immunosorbent assay (ELISA). A large number of genes, including matrix metalloproteinases, collagens and cytokines as well as genes involved in osteochondral development, were differentially expressed in the A+(Pos) compared with A+(Neg). Moreover, a series of genes (notably CCL18) was differentially expressed both in the A+(Neg) and A+(Pos) compared with the A0. A significant increase of CCL18 was also found at the protein level in the aortic wall and in peripheral blood of A+ patients compared with A0. In conclusion, new factors, including CCL18, involved in the progression of AAA and, potentially, in their rupture were identified by a genome-wide analysis of PET-positive and -negative human aortic tissue samples. Further work is needed to study their role in AAA destabilization and weakening.

The GLO1 C332 (Ala111) allele confers autism vulnerability: family-based genetic association and functional correlates

Glyoxalase I (GLO1) is a homodimeric Zn(2+)-dependent isomerase involved in the detoxification of methylglyoxal and in limiting the formation of advanced glycation end-products (AGE). We previously found the rs4746 A332 (Glu111) allele of the GLO1 gene, which encodes for glyoxalase I, associated with "unaffected sibling" status in families with one or more children affected by Autism Spectrum Disorder (ASD). To identify and characterize this protective allele, we sequenced GLO1 exons and exon-intron junctions, detecting two additional SNPs (rs1049346, rs1130534) in linkage disequilibrium with rs4746. A family-based association study involving 385 simplex and 20 multiplex Italian families yielded a significant association with autism driven only by the rs4746 C332 (Ala111) allele itself (P < 0.05 and P < 0.001 under additive and dominant/recessive models, respectively). Glyoxalase enzymatic activity was significantly reduced both in leukocytes and in post-mortem temporocortical tissue (N = 38 and 13, respectively) of typically developing C332 allele carriers (P < 0.05 and <0.01), with no difference in Glo1 protein levels. Conversely, AGE amounts were significantly higher in the same C332 post-mortem brains (P = 0.001), with a strong negative correlation between glyoxalase activity and AGE levels (τ = -0.588, P < 0.01). Instead, 19 autistic brains show a dysregulation of the glyoxalase-AGE axis (τ = -0.209, P = 0.260), with significant blunting of glyoxalase activity and AGE amounts compared to controls (P < 0.05), and loss of rs4746 genotype effects. In summary, the GLO1 C332 (Ala111) allele confers autism vulnerability by reducing brain glyoxalase activity and enhancing AGE formation, but years after an autism diagnosis the glyoxalase-AGE axis appears profoundly disrupted, with loss of C332 allelic effects.