Altered tubulin assembly dynamics with N-homocysteinylated human 4R/1N tau in vitro

Tau isoforms promote neuronal integrity through binding and stabilization of microtubule proteins (MTP). It has been shown that hyperphosphorylation of tau contributes to Alzheimer’s disease (AD) pathology and related tauopathies. However, other pathogenic modifications of tau have not been well characterized. It is well accepted that elevated level of homocysteine (Hcy) is associated with neurodegenerative diseases such as AD. As a result of N-homocysteinylation of lysine residues, Hcy becomes a component of proteins, as a protein–homocystamide adduct, which affects protein structure and function. Here we demonstrate that N-homocysteinylation of human tau (4R/1N isoform) inhibits its function via impaired tau–tubulin specific binding and MTP assembly dynamics in vitro.     

The interaction of beta-lactoglobulin with ciprofloxacin and kanamycin; a spectroscopic and molecular modeling approach

A vast research has been conducted to find suitable and safe carriers for vital and pH-sensitive drugs including antibiotics. This article reports the use of easily accessible and abundant purified beta-lactoglobulin (β-LG) protein as the potential carrier of widely used Kanamycin (Kana) and Ciprofloxacin (Cip) antibiotics. Spectroscopic techniques (Fluorescence, UV–vis, Circular Dichroism) combined with molecular docking were used to determine the binding mechanism of these drugs. Fluorescence studies showed moderate binding affinity with the calculated binding constants K_Cip = 60.1 (±0.2)?×?10³ M^?1 and K_kana = 2.5 (±0.6)?×?10³ M^?1 with the order of Cip > Kana. Results of UV–vis were consistent with fluorescence measurements and demonstrated a stronger complexation for Cip rather than Kana. The secondary structure of β-LG was preserved upon interaction with Kana; however, a reduction in β-sheet content from 39.1 to 31.9% was convoyed with an increase in α-helix from 12.8 to 20.5% due to complexation of Cip. Molecular docking studies demonstrated that preferred binding sites of these drugs are not the same and several amino acids are involved in stabilizing the interaction. Based on the achieved results, Kana and Cip can spontaneously bind to β-LG and this protein may serve as their transport vehicle.     

Adiponectin and Leptin Trajectories in Mexican-American Children from Birth to 9 Years of Age

Objectives

To address molecular mechanisms underlying obesity development, we examined patterns of critical metabolism-related hormones, adiponectin and leptin (adipokines), over childhood.

Subjects and Design

Plasma adiponectin and leptin were measured in 80 Mexican-American children at birth and again at 2, 5, and 9 years from the ongoing prospective cohort followed by the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS). We used a mixture modeling approach to identify patterns in adipokine trajectories from birth to 9 years.

Results

Leptin was positively related to child body size within all ages, however adiponectin had inverse and weaker associations with BMI at 2, 5, and 9 years. Correlations between adipokine levels over the 0–2, 2–5, and 5–9-year periods increased for both leptin (r = 0.06, 0.31 and 0.62) and adiponectin (r = 0.25, 0.41 and 0.46). Our mixture modeling approach identified three trajectory clusters for both leptin (1L [slowly-rising], 2L [rapidly-rising], and 3L [stable]) and adiponectin (1A [steep-dropping and rebounding], 2A [moderately-dropping], and 3A [stable]). While leptin groups were most separated over the 2–9-year period, adiponectin trajectories displayed greatest heterogeneity from birth to 2 years. Children in the rapidly-rising 2L group had highest BMI and waist circumference at 9 years. Further, children with greater birth weight had increased odds of belonging to this high risk group (OR = 1.21 95% CI 1.03, 1.43, compared to stable group 3L). Children whose mothers consumed more sugar-sweetened beverages during pregnancy were at risk of being in the steep-dropping 1A group (OR = 1.08, 95% CI 1.01, 1.17, compared to stable group 3A).

Conclusion

Our results highlight developmental differences in leptin and adiponectin over the childhood period. Leptin closely reflects child body size however factors affecting adiponectin and long-term consequences of its changes over infancy need to be further explored.     

MicroRNA-590-3P suppresses cell survival and triggers breast cancer cell apoptosis via targeting sirtuin-1 and deacetylation of p53

Downregulation of microRNA-590-3p (miR-590-3p) is a frequently occurring, nonphysiological event which is observed in several human cancers, especially breast cancer. However, the significance of miR-590-3p still remain unclear in the progression of this disease. This study explored the role of miR-590-3p in apoptosis of breast cancer cells. Gene expression of miR-590-3p, Sirtuin-1 (SIRT1), Bcl-2 associated X protein (BAX), and p21 was evaluated with real-time polymerase chain reaction (PCR) and SIRT1 protein expression was assessed by Western blot analysis in breast cancer cell lines. Bioinformatics analysis and luciferase reporter assay were used to evaluate targeting of SIRT1 messenger RNA (mRNA) by miR-590-3p. Cells were transfected with miR-590-3p mimic and inhibitor and their effects on the expression and activity of SIRT1 were evaluated. The effects of miR-590-3p upregulation on the acetylation of p53 as well as cell viability and apoptosis were assessed by Western blot analysis, WST-1 assay, and flow cytometry, respectively. miR-590-3p expression was considerably downregulated in breast cancer cells which was accompanied by upregulation of SIRT1 expression. SIRT1 was recognized as a direct target for miR-590-3p in breast cancer cells and its protein expression and activity was dramatically inhibited by the miR-590-3p. In addition, there was an increase in p53 and its acetylated form that ultimately led to upregulation of BAX and p21 expression, suppression of cell survival, and considerable induction of apoptosis in breast cancer cells. These findings suggest that miR-590-3p exerts tumor-suppressing effects through targeting SIRT1 in breast cancer cells, which makes it a potential therapeutic target for developing more efficient treatments for breast cancer.     

Melatonin: An important anticancer agent in colorectal cancer

Colorectal cancer is one of the most common cancers among the elderly, which is also seen in the forms of hereditary syndromes occurring in younger individuals. Numerous studies have been conducted to understand the molecular and cellular pathobiology underlying colorectal cancer. These studies have found that cellular signaling pathways are at the core of colorectal cancer pathology. Because of this, new agents have been proposed as possible candidates to accompany routine therapy regimens. One of these agents is melatonin, a neuro-hormone known best for its essential role in upholding the circadian rhythm and orchestrating the many physiologic changes it accompanies. Melatonin is shown to be able to modulate many signaling pathways involved in many essential cell functions, which if deregulated cause an accelerated pace towards cancer. More so, melatonin is involved in the regulation of immune function, tumor microenvironment, and acts as an antioxidant agent. Many studies have focused on the beneficial effects of melatonin in colorectal cancers, such as induction of apoptosis, increased sensitivity to chemotherapy agents and radiotherapy, limiting cellular proliferation, migration, and invasion. The present review aims to illustrate the known significance of melatonin in colorectal cancer and to address possible clinical use.     

Endothelial cells' biophysical,biochemical, and chromosomal aberrancies in high‐glucose condition within the diabetic range

To date, many studies have been conducted to find out the underlying mechanisms of hyperglycemia‐induced complications in diabetes mellitus, attributed to the cellular pathologies of different cells—especially endothelial cells. However, there are still many ambiguities and unresolved issues to be clarified. Here, we investigated the alteration in biophysical and biochemical properties in human umbilical vein endothelial cells exposed to a high‐glucose concentration (30mM), comparable to glucose content in type 2 diabetes mellitus, over a course of 120 hours. In addition to a reduction in the rate of cell viability and induction of oxidative stress orchestrated by the high‐glucose condition, the dynamic of the fatty acid profile—including polyunsaturated, monounsaturated, and saturated fatty acids—was also altered in favor of saturated fatty acids. Genetic imbalances were also detected at chromosomal level in the cells exposed to the abnormal concentration of glucose after 120 hours. Moreover, the number of tip cells (CD31⁺/CD34⁺) and in vitro tubulogenesis capability negatively diminished in comparison to parallel control groups. We found that diabetic hyperglycemia was associated with a decrease in the cell‐cell tight junction and upregulation in vascular endothelial cadherin and zonula occludens (ZO)‐1 molecules after 72 and 120 hours of exposure to the abnormal glucose concentration, which resulted in a profound reduction in transendothelial electrical resistance. The surface plasmon resonance analysis of the human umbilical vein endothelial cells immobilized on gold‐coated sensor chips confirmed the loosening of the cell to cell intercellular junction as well as stable attachment of each cell to the basal surface. Our findings highlighted the disturbing effects of a diabetic hyperglycemia on either biochemical or biophysical properties of endothelial cells.