Biochimie最新文献

Melatonin, a hormone primarily synthesized in the pineal gland, has an essential role in the regulation of various physiological processes, such as the sleep-wake cycle, immune function, and antioxidative responses. Emerging evidence suggests that melatonin also exerts significant protective effects against skin cancers, particularly melanoma and non-melanoma skin cancers. This review aims to provide a comprehensive overview of melatonin's multifaceted mechanisms of action in preventing and treating skin cancers, focusing on its antioxidant, photoprotective, and radioprotective properties. Melatonin's capability to modulate skin cancer's related key signaling pathways underscores its complex yet potent anticancer mechanisms. Furthermore, synergistic effects between melatonin and conventional oncology treatments, such as radiotherapy, chemotherapy, and targeted therapies, hold promise for improving treatment outcomes while mitigating adverse effects. However, while melatonin shows great potential as an adjunct in oncology treatment regimens, further research is needed to optimize its clinical applications and fully understand its safety profile and potential side effects. Overall, elucidating melatonin's role in skin cancer prevention and treatment represents a promising avenue for advancing cancer therapeutics and improving patient outcomes.

Actin filaments play an essential role in the process of oocyte maturation and completion of meiosis. However, whether the localization of F-actin in the ooplasm is associated with normal completion of the second meiotic division remains unclear. Mitochondrial distribution is another important parameter correlating directly with MII oocyte capacity to finalize meiosis. Our objective was to examine the role of actin microfilaments in the distribution of mitochondria and, respectively, Metaphase II (MII) oocytes meiotic potential. We show monoclonal antibody-mediated inhibition of actin polymerization in young mouse oocytes, reduction of the amount of F-actin, and induction of mitochondrial clustering induced by antibody treatment. Similar phenotype, even in untreated eggs, was observed in in vitro oocyte aging experiments. Observed changes correlate with reduced ability of MII oocytes to extrude the second polar body and form the pronuclei. Changes in colocalization of F-actin and mitochondria likely resulted from disturbed cytoskeleton architecture. The perturbations in the amount of F-actin and its distribution largely coincide with mitochondrial redistribution. Based on these data, we suggest actin microfilament's participation in redistribution of mitochondria during MII oocyte aging in vitro. Accordingly, patterning of F-actin is indicative of high rate of the completed second meiotic division. These results help evaluating oocyte's quality and choosing optimal time between placement into culture and in vitro fertilization.

Human thymic stromal lymphopoietin (TSLP) is a pro-inflammatory cytokine located at the top of inflammatory cascade that makes it a promising therapeutic target in allergic asthma. The cell surface receptor of TSLP is a heterodimer consisting of a TSLP receptor (TSLPR) and an interleukin-17 receptor α (IL-7Rα). The TSLPR subunit should be first added to the free TSLP to form a TSLPR/TSLP pre-complex, which further recruits the IL-7Rα subunit to obtain the final TSLPR/IL-7Rα/TSLP complex. Previous works have been focused on targeting the IL-7Rα-binding site of TSLP. Instead, we herein reported an attempt for rational design of cyclic peptidic inhibitors to competitively disrupt the TSLPR-TSLP interaction based on their complex crystal structure by integrating dynamics simulation and energetics analysis as well as experimental assays at molecular level. An interfacial peptide segment derived from the hotspots of TSLPR that cover a specific TSLP-binding site on the TSLPR interface, which is expected to natively form a U-shaped conformation recognized by TSLP and thus compete with the cognate TSLPR for TSLP. The eS4P peptide was further stapled by a disulfide bridge between different residue pairs across its two arms, thus separately resulting in its two stapled cyclic counterparts, i.e. eS4P[189-198] and eS4P[188-200] peptides. Circular dichroism characterized that the stapling can effectively constrain the peptide into a native-like U-shpared conformation in free state, thus largely minimizing the entropy penalty upon its binding to TSLP. Affinity assays revealed that the stapling can considerably improve the peptide binding potency to TSLP by 2.9-fold and 8.3-fold at molecular level. In addition, we further demonstrated that the potent eS4P[188-200] peptide has a good selectivity for its cognate TSLP over other four noncognate cytokines IL-2, IL-7, IL-13 and IL-22 that are relevant with the TSLP. In this respect, it is considered that the disulfide-stapled cyclic peptide-mediated blockade of TLSP inflammatory cascade may be a new and promising therapeutic strategy against allergic asthma.

5,10-Methylenetetrahydrofolate reductase (MTHFR) is a folate cycle enzyme required for the intracellular synthesis of methionine. MTHFR was previously shown to be partially phosphorylated at 16 residues, which was abrogated by conversion of threonine 34 to alanine (T34A) or truncation of the first 37 amino acids (i.e. expression of amino acids 38-656), and promoted by methionine supplementation. Here, we over-expressed wild-type MTHFR (MTFHR_WT), as well as the variants MTHFR_T34A and MTHFR_38-656 in 293T cells to provide further insights into these mechanisms. We demonstrate that following incubation in high methionine conditions (100-1000 μM) MTHFR_WT is almost completely phosphorylated, but in methionine restricted conditions (0-10 μM) phosphorylation is reduced, while MTHFR_T34A always remains unphosphorylated. Following affinity purification coupled mass spectrometry of an empty vector, MTHFR_WT, MTHFR_T34A and MTHFR_38-656 in three separate experiments, we identified 134 proteins consistently pulled-down by all three MTHFR protein variants, of which 5 were indicated to be likely true interactors (SAINT prediction threshold of 0.95 and 2 fold-change). Amongst these were the folate cycle enzyme methylenetetrahydrofolate dehydrogenase (MTHFD1) and the amino acid starvation sensor general control nonderepressible 1 (GCN1). Immunoprecipitation-immunoblotting of MTHFR_WT replicated interaction with both proteins. An AlphaFold 3 generated model of the MTHFR-MTHFD1 interaction places the MTHFD1 dehydrogenase/cyclohydrolase domain in direct contact with the MTHFR catalytic domain, suggesting their interaction may facilitate direct delivery of methylenetetrahydrofolate. Overall, we confirm methionine availability increases MTHFR phosphorylation, and identified potential interaction of MTHFR with MTHFD1 and GCN1.

Dynamic epigenetic control is essential for proper spermatogenesis. Spermatogenesis is a unique mechanism that includes recombination, meiosis, and the conversion of histones to protamines. Epigenetics refers to the ability to modify gene expression without affecting DNA strands directly and helps to regulate the dynamic gene expression throughout the differentiation process of spermatogonium stem cells. Histone alterations and DNA methylation control the epigenome. While histone modifications can result in either expression or repression depending on the type of modification, the type of histone protein, and its specific residue, histone acetylation is one of the changes that typically results in gene expression. Histone acetyltransferases (HATs) add an acetyl group to the amino-terminal of the core histone proteins, causing histone acetylation. On the other hand, histone deacetylases (HDACs) catalyze histone deacetylation, which is linked to the suppression of gene expression. This review highlights the significance of HATs and HDACs during mammalian spermatogenesis and focuses on what is known about changes in their expression.

Continuing our search for metal drugs with markedly higher toxicity to cancer cells than to normal cells, we evaluated the effect of 2,2'-bipyridine (bpy) as a co-ligand in the compounds [Cu(μ-O,O'-NO₃)(l-Arg)(bpy)]NO₃}_n (1), [CuCl(l-Arg)(bpy)]Cl·3H₂O (2) (l-Arg= l-arginine), on DNA interaction, cytotoxic and antiproliferative activity, compared to the effects induced by other co-ligands i.e. 1,10-phenanthroline (phen) and SCN^- ions, in similar Cu(II) compounds we have studied previously. Potentiometric, EPR and UV-Vis experiments were first used to structurally characterise the complexes formed in solutions 1 and 2 and in model Cu(II)/bpy/l-Arg systems. Gel electrophoresis in the presence of H₂O₂ was used to identify DNA damage by 1 and 2. In addition, cyclic voltammetry of both compounds was performed to confirm the existence of Cu(II)/Cu(I) redox pairs involved in the free radical mechanism of this DNA damage. The DNA binding constants of 1 and 2 were determined spectrophotometrically. The selectivity of the cytotoxic and antiproliferative activity of compounds 1 and 2 was tested in vitro against human lung adenocarcinoma (A549), liver cancer (HepG2) and normal cells in comparison with those previously observed by us for compounds consisting of phen and SCN^- ligands. Molecular docking calculations were performed for [Cu(l-Arg)(bpy)]²⁺ (present in solutions of 1 and 2) interacting with B-DNA (aureolin), metalloproteinase (S. aureus) and penicillin-binding protein (E. coli) to determine the nature of the complex-receptor interaction, potential binding modes and energies.

Alpha-1 antitrypsin (A1AT) is the major circulating serine protease inhibitor. Hypersialylated glycoforms (HSG) are produced to boost A1AT anti-inflammatory and anti-protease properties. Their occurrence and prognostic impact outside severe COVID-19 or community-acquired pneumonia are unknown. Our aim was to clarify the occurrence of A1AT functional deficiency and HSG in patients admitted into intensive care unit (ICU) for any cause. A1AT and elastase inhibitory capacity (EIC) were measured in serum. Functional A1AT deficiency was defined by a measured EIC/calculated EIC Ratio ≤0.85. HSG were identified by isoelectrofocusing and quantified by gel densitometry. A total of 248 serum samples was analyzed , 173 from COVID-19 and 75 from non COVID-19 patients. A functional A1AT deficiency occurred 3-fold more frequently in non-COVID-19 than in COVID-19 patients: 18.7% vs 6.9% and was not associated with more frequent S/Z deficient alleles. Functional deficiency was also more frequent in deceased than alive patients in COVID-19 group. M0 and M1 HSG of A1AT occurred in around half of patients but the relative proportion of M1 significantly increased in deceased vs alive patients only in the non-COVID-19 group explaining the absence of worsening of the functional deficiency. In conclusion, our study shows that a functional A1AT deficiency is more frequently observed in patients admitted to the ICU for a cause unrelated to COVID-19, as well as in those with an unfavorable evolution. Among the latter, only those admitted for non-COVID-19 tried to compensate the functional deficiency by increasing the proportion of M1 HSG of A1AT.

Traditionally recognised as the energy reservoir and main site of adaptive thermogenesis, white and brown adipose tissues are complex endocrine organs regulating systemic energy metabolism via the secretion of bioactive molecules, termed "adipokines" and "batokines", respectively. Due to its significant role in regulating whole-body energy metabolism and other physiological processes, adipose tissue has been increasingly explored as a feasible therapeutic target for obesity. Flavonoids are one of the most significant plant polyphenolic compounds holding a great potential as therapeutic agents for combating obesity. However, understanding their mechanisms of action remains largely insufficient to formulate therapeutic theories. This review critically discusses scientific evidence highlighting the role of flavonoids in ameliorating obesity-related metabolic complications, including adipose tissue dysfunction, inflammation, insulin resistance, hepatic steatosis, and cardiovascular comorbidities in part by modulating the release of adipokines and batokines. Further discussion advocates for the use of therapeutics targeting these bioactive molecules as a potential avenue for developing effective treatment for obesity and its adverse metabolic diseases such as type 2 diabetes.

The Structural Maintenance of Chromosome (SMC) protein is essential for various cellular processes, including chromosome organization, DNA repair, and genome stability. MksB, an alternative SMC protein present in prokaryotes, comprises a hinge dimerization domain and an ABC ATPase head domain linked by a coiled-coil arm. While hinge dimerization in bacterial and eukaryotic SMCs is attributed to conserved glycines, our study unveils the critical role of a novel KDDR motif located at a loop near the hinge dimer interface in Mycobacterium smegmatis MksB (MsMksB). We demonstrate the regulatory role of this motif in MsMksB dimerization and DNA binding activity. The K600D mutation in the KDDR motif induces MsMksB dimer-to-monomer conversion, highlighting the significance of this motif in MsMksB dimerization. Mass spectrometry-based mapping of the DNA binding site revealed the lysine's involvement in protein-DNA interaction. Monomers of the hinge domain lose DNA binding activity, and MsMksB single-arm mutants exhibit reduced DNA binding and ATPase activity, underscoring the importance of hinge-mediated dimerization in MsMksB function. Notably, the R603D mutant retains dimerization but shows compromised ATPase and DNA binding activities. Mutants with defective ATPase activity exhibit impaired DNA condensation in vivo. These findings provide novel regulatory insight into the mechanism of MksB dimerization and DNA binding, uncovering the fundamental processes of chromosome condensation and segregation.

Elevated fasting plasma total homocysteine (tHcy) and the methylenetetrahydrofolate reductase C677T polymorphism (rs1801133) have been associated with hypertension. Whether the L-Arginine pathway is involved, is unclear. We aimed to investigate whether the association between tHcy, the rs1801133 polymorphism and hypertension involves the L-Arginine pathway. THcy, plasma folate and cobalamin, erythrocyte glutathionine reductase activation coefficient, rs1801133 genotype, plasma L-Arginine, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) were determined in a cross-sectional study of 788 adults (aged 18 to 75), randomly selected from 2 town population registers. Participants participated in a medical checkup and provided a fasting blood sample. Associations between tHcy, rs1801133 genotype and L-Arginine pathway metabolites were assessed by multiple linear regression analysis and whether the tHcy and rs1801133 genotype are associated with hypertension via the L-Arginine pathway was investigated using mediation analysis. tHcy was positively associated with ADMA (B=0.003; SE=0.001; P<0.001) and SDMA (B=0.007; SE=0.002; P<0.001) and negatively associated with the L-Arginine/ADMA (B=-1.140; SE=0.451; P<0.05) and ADMA/SDMA (B=-0.006; SE=0.003; P<0.05) ratios. The MTHFR 677 CT vs CC genotype was negatively associated with ADMA (B=-0.013; SE=0.007; P<0.05) and with SDMA (B=-0.029; SE=0.013; P<0.05) in participants under 50 years. Each standard deviation increase (37.6) in the L-Arginine/ADMA ratio was associated with reduced hypertension risk (OR [95%CI], 0.6 [0.5, 0.8]). Mediation analysis showed that tHcy and ADMA were mediators in the association between the rs1801133 TT vs CC genotypes and hypertension. Our results support the L-Arginine pathway as a mediator in the association of impaired One-Carbon metabolism and hypertension.