Glucose but not N-acetylglucosamine accelerates in vitro senescence of human peritoneal mesothelial cells

Determination and Correlation of Solubility of N-Acetylglucosamine in Four Aqueous Binary Solvents from 283.15 to 323.15 K

N-Acetylglucosamine (NAG) is a significant novel functional monosaccharide with a wide range of potential applications, such as in the medical and cosmetic fields. A gravimetric technique was used to assess the solubility of NAG in water, methanol, N,N-dimethylformamide, water + methanol, water + n-propanol, water + N,N-dimethylformamide, and water + acetonitrile at temperatures ranging from 283.15 to 323.15 K. The outcomes of the experiment demonstrated that the temperature and water content were positively correlated with the solubility of NAG in four experimental binary solvents. The order of solubility in the four aqueous solvent mixtures is water + DMF > water + methanol > water + n-propanol > water + acetonitrile. The solubility data was well correlated using the modified Apelblat model, the CNIBS/R-K model, and the Apelblat-Jouyban-Acree model. Experimental data from NAG will help guide the design of cooling and dissolution in crystallization processes.

Scavenging of reactive oxygen species by astaxanthin inhibits epithelial-mesenchymal transition in high glucose-stimulated mesothelial cells

BACKGROUND

High glucose concentrations influence the functional and structural development of the peritoneal membrane. We previously reported that the oral administration of astaxanthin (AST) suppressed peritoneal fibrosis (PF) as well as inhibited oxidative stress, inflammation, and epithelial-mesenchymal transition (EMT) of peritoneal mesothelial cells (PMCs) in a chlorhexidine-induced PF rat model. This suggests that oxidative stress induction of EMT is a key event during peritoneal damage. The present study evaluated the therapeutic effect of AST in suppressing EMT, in response to glucose-induced oxidative stress.

METHODS

Temperature-sensitive mesothelial cells (TSMCs) were cultured in the presence or absence of AST and then treated with 140 mM glucose for 3 or 12 hours. Expression levels of TNF-α, TGF-β, and VEGF were determined at the mRNA and protein levels, and nuclear factor kappa B (NF-κB) activity was evaluated. We measured NO2-/NO3- concentrations in cellular supernatants and determined 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in mitochondrial and nuclear DNA. The expressions of E-cadherin and alpha-smooth muscle actin (α-SMA) were evaluated by double immunofluorescence and protein levels.

RESULTS

High glucose concentrations induced overproduction of reactive oxidative species (ROS), increasing 8-OHdG mitochondrial DNA and cytokine levels. The NF-κB pathway was activated in response to high glucose concentrations, whereas de novo α-SMA expression was observed with decreased E-cadherin expression. AST treatment attenuated ROS production, inflammatory cytokine production, NF-κB activation, and EMT.

CONCLUSION

The findings of the present study indicate that AST may have an anti-EMT effect due to anti-oxidative and anti-inflammatory activities by scavenging glucose-induced ROS from mitochondria in PMCs. AST may be an efficacious treatment for PF.

Regulation of synthesis and roles of hyaluronan in peritoneal dialysis

Hyaluronan (HA) is a ubiquitous extracellular matrix glycosaminoglycan composed of repeated disaccharide units of alternating D-glucuronic acid and D-N-acetylglucosamine residues linked via alternating β-1,4 and β-1,3 glycosidic bonds. HA is synthesized in humans by HA synthase (HAS) enzymes 1, 2, and 3, which are encoded by the corresponding HAS genes. Previous in vitro studies have shown characteristic changes in HAS expression and increased HA synthesis in response to wounding and proinflammatory cytokines in human peritoneal mesothelial cells. In addition, in vivo models and human peritoneal biopsy samples have provided evidence of changes in HA metabolism in the fibrosis that at present accompanies peritoneal dialysis treatment. This review discusses these published observations and how they might contribute to improvement in peritoneal dialysis.

N-Acetylglucosamine modulates function of the skin fibroblasts

BACKGROUND

Fibroblasts are an important component of the skin determining its properties. N-Acetylglucosamine (NAG) is the substrate for hyaluronan synthesis, and it also has anti-inflammatory and anti-senescent activity in mesothelial cells.

METHODS

We tested in in vitro-cultured human skin fibroblasts how supplementation of culture medium with NAG 10 mmol L(-1) changes properties of these cells.

RESULTS

Fibroblasts cultured in presence of NAG produced more proteins and that was mainly due to increased synthesis of collagen (+33% vs. control, P < 0.05). Hyaluronan synthesis was increased (+107% vs. control, P < 0.001), but interleukin-6 synthesis was reduced (-22% vs. control, P < 0.05). Fibroblasts cultured in medium with NAG 10 mmol L(-1) demonstrated improved ability to heal the injured layer of cells (+34% vs. control, P < 0.05). Additionally senescence of fibroblasts undergoing replicative ageing in the presence of NAG was less pronounced, as reflected by smaller increase in the population doubling time (-70% vs. control, P < 0.05).

CONCLUSION

We conclude that NAG induced changes in the skin fibroblasts' properties maybe important for prevention of the age-dependent changes in its structure and function.

Mesothelial cell: a multifaceted model of aging

Human peritoneal mesothelial cells (HPMCs) dominate within the peritoneal cavity and thus play a central role in a variety of intraperitoneal processes, including the transport of water and solutes, inflammation, host response, angiogenesis, and extracellular matrix remodeling. In addition, they contribute to the development of abdominal adhesions, peritonitis, endometriosis, cancer cell metastases, and peritoneal dialysis complications. For less than a decade the primary cultures of omental HPMCs have also been used as an experimental tool in studies on cellular aging. This paper provides the first comprehensive overview of the current state of art on molecular mechanisms underlying HPMC senescence in vitro. Special attention is paid to the causes of the very fast dynamics of HPMC senescence, and in particular to the role of non-telomeric DNA damage, the autocrine activity of TGF-β1, and the causative effects of oxidative stress. In addition, some clinical manifestations of HPMC senescence will be discussed, including its interplay with organismal aging, peritoneal dialysis, and cancer progression.