Depletion of glycosphingolipids induces excessive response of chondrocytes under mechanical stress

Glycosphingolipids (GSLs) are ubiquitous membrane components that play an indispensable role in maintaining chondrocyte homeostasis. To gain better insight into roles of GSLs, we studied the effects of GSL-deletion on the physiological responses of chondrocytes to mechanical stress. Mice lacking Ugcg gene (Ugcg^-/-) were genetically generated to obtain GSL-deficient mice, and their chondrocytes from the joints were used for functional analyses in vitro culture experiments. The cells were seeded in a three-dimensional collagen gel and subjected to 5%, 10% or 16% cyclic tensile strain for either 3 or 24 h. The gene expressions of chondrocyte anabolic and catabolic factors, and the induction of Ca²⁺ signaling were analyzed. Our results revealed that chondrocytes derived from GSL-deficient mice exhibited an elevation in the expression of catabolic factors (ADAMTS-5, MMP-13) following the exposure to strain with amplitudes of 10%. Likewise, applying cyclic tensile strain with these amplitudes resulted in an increased Ca²⁺ oscillation ratio in chondrocytes from GSL-deficient as compared to the ratio from control mice. These results demonstrated that deletion of GSL stimulated the catabolic responses of chondrocytes to mechanical stress via the augmentation of the sensitivity to mechanical stress that may lead to the cartilage deterioration. These findings suggest that the regulation of the physiological responses of chondrocytes by GSLs could be a potential target in a therapeutic intervention in osteoarthritis.     

Regulation of the rat interstitial collagenase promoter by IL-1β, c-Jun,and ras-dependent signaling in growth plate chondrocytes

In an attempt to better define molecular influences on rat interstitial collagenase gene expression in cartilage, the promoter function was characterized using transient transfection assay, electrophoresis mobility shift assay, and genetic analysis in isolated growth plate chondrocytes. Data from 5′-flanking deletion and selected mutations suggest that multiple cis elements in both the proximal and distal regions of the promoter were important in the regulation of promoter activity. A proximal tumor response element (TRE) was shown to be necessary for basal and interleukin (IL)-1β–inducible reporter gene activity. Cells stimulated by IL-1β (1 ng/ml; 18 h) had elevated TRE binding activity, and one of the factors involved was identified as the nuclear protein, c-Jun. Indeed, c-Jun directed antisense oligonucleotides reduced rat interstitial collagenase mRNA. A sense oligonucleotide was ineffective. Regulation of promoter activity was susceptible to Ras-dependent signaling as expression of dominant negative mutant of Ras kinase (pZIP-RasN17) reduced reporter gene activity. In a comparison of proximal promoter reporter plasmid activity between proliferative and hypertrophic cells, inhibition of Ras-dependent signaling was less effective in the later cell type. This study suggests that the activation of nuclear binding proteins that bind TRE may be a common event with IL-1β regulation. Moreover, these data suggest that the regulation of rat interstitial collagenase gene expression is a combinatorial process and multiple cis-acting regulatory sites may interact to exert different effects dependent on the stage of chondrocyte differentiation. J. Cell. Biochem. 67:92–102, 1997. Published 1997 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Neutrophil apoptosis: A target for enhancing the resolution of inflammation

Neutrophils are essential for host defense and their programmed cell death and removal are critical for the optimal expression as well as for efficient resolution of inflammation. Delayed neutrophil apoptosis or impaired clearance of apoptotic neutrophils by macrophages contributes to the progression of chronic inflammation. Under most conditions, neutrophils are exposed to multiple factors and their fate would ultimately depend on the balance between pro‐survival and pro‐apoptotic signals. Life or death decisions are tightly controlled by a complex network of intracellular signaling pathways. Accumulating data indicate that receptors, such as the formyl peptide receptor 2/lipoxin receptor or β₂‐integrins can generate contrasting cues in neutrophils in a ligand‐specific manner and suggest a hierarchy among these signals. In this article, we review recent advances on how pro‐apoptosis and pro‐survival signals interact to determine the fate of neutrophils and the inflammatory response, and highlight novel pharmacological strategies that could be used to enhance the resolution of inflammation by redirecting neutrophils to apoptosis. J. Cell. Biochem. 108: 1039–1046, 2009. © 2009 Wiley‐Liss, Inc.     

Different conversion metabolic rates of testosterone are associated to hormone-sensitive status and -response of human prostate cancer cells

The main goal of the present work was to compare the ability of human prostate cancer (PCa) cells to metabolize testosterone (T) in living conditions. To this end we studied three different human PCa cell lines (LNCaP, DU145 and PC3) having different hormone-sensitive status and capability of response to androgens. We used an original approach which allows the evaluation of conversion metabolic rates in growing cells after administration of labeled steroid precursor (presently T), at physiological concentrations (1–10 nM). Analysis of both precursor degradation and formation of several products was carried out using reverse phase-high performance liquid chromatography (RP-HPLC) and “on line” radioactive detection. Comparison of the three human PCa cells revealed that their metabolic aptitude differed in many respects: (i) rates of precursor degradation, (ii) different products' formation, and (iii) extent of conjugate production. In detail, PC3 cells quickly degraded T and exhibited high formation rates of androstenedione (A-4-ene-Ad); both DU145 and LNCaP cells mostly retained high levels of unconverted T, with a limited production of A-4-ene-Ad and its 17-keto derivatives (if any). Either LNCaP or DU145 cells generated a relatively high amount of dihydrotestosterone (DHT). In contrast, neither DHT nor its main metabolites were detected in PC3 cells at both short and longer incubation times. As expected, T degradation and A-4-ene-Ad production were highly correlated (r = 0.97; P < 0.03); similarly, A-4-ene-Ad and DHT formation showed a negative, significant correlation. Negligible production of conjugates was noted in both PC3 and DU145 cells, whilst it was remarkable in LNCaP cells (ranging from 43 to 57%). Overall, our data indicate that human PCa cells degrade T quite differently, favoring alternatively reductive or oxidative patterns of androgen metabolism.     

Protective effects of antioxidant combination against D‐galactosamine‐induced kidney injury in rats

The protective effects of an antioxidant combination in kidney injury induced by the injection of D‐galactosamine (D‐GaIN) were examined in the present study. Sprague Dawley female rats were used and divided into four groups as follows: (1) animals injected physiological saline solution, intraperitoneally, (2) animals treated with the combination of ascorbic acid (100 mg kg^?1 day^?1), β‐carotene (15 mg kg^?1 day^?1), α‐tocopherol (100 mg kg^?1 day^?1), and sodium selenate (0.2 mg kg^?1 day^?1) for three days orally, (3) rats injected D‐GaIN (500 mg kg^?1) intraperitoneally as a single dose, and (4) animals treated with the antioxidant combination for three days, then injected D‐GaIN. The tissue and blood samples of animals were collected for morphological and biochemical evaluations. Histopathological injury in kidney tissues was observed together with a significant increase in tissue lipid peroxidation (LPO) level, myeloperoxidase (MPO), lactate dehydrogenase, catalase and superoxide dismutase (SOD) activities, and serum creatinine and urea levels, and a significant decrease in glutathione level and glutathione peroxidase activity in D‐GaIN injected rats. However, a decrease in the degenerative changes was detected in the kidney tissue of D‐GaIN + antioxidant group, and biochemical results showed reversed effects. In conclusion, it seems reasonable to conclude that the treatment of the antioxidant combination has a protective effect on D‐GaIN‐induced kidney injury of rats. Copyright © 2010 John Wiley & Sons, Ltd.     

Rosmarinic acid down‐regulates NO and PGE2 expression via MAPK pathway in rat chondrocytes

Rosmarinic acid (RosA) is a water‐soluble polyphenol, which can be isolated from many herbs such as orthosiphon diffuses and rosmarinus officinalis. Previous studies have shown that RosA possesses various biological properties. In this study, we investigate the anti‐osteoarthritic effects of RosA in rat articular chondrocytes. Chondrocytes were pre‐treated with RosA, followed by the stimulation of IL‐1β. Real‐time PCR and Western blot were performed to detect the expression of matrix metalloproteinase (MMP)‐1, MMP‐3 and MMP‐13. Nitric oxide and PGE₂ production were measured by Griess reagent and enzyme‐linked immunosorbent assay (ELISA). The expression of mitogen‐activated protein kinase (MAPK) and nuclear factor‐κB (NF‐κB) was also investigated by Western blot analysis. We found that RosA down‐regulated the MMPs expression as well as nitric oxide and PGE₂ production in IL‐1β‐induced chondrocytes. In addition, RosA inhibited p38 and JNK phosphorylation as well as p65 translocation. The results suggest that RosA may be considered a possible agent in the treatment of OA.     

Characterization of mice deficient in interleukin-1β converting enzyme

Interleukin-1β converting enzyme (ICE) processes the inactive proIL-1β to the proinflammatory mature IL-1β. ICE belongs to a family of cysteine proteases that have been implicated in apoptosis. To address the biological functions of ICE, we generated ICE-deficient mice through gene targeting technology. ICE-deficient mice developed normally, appeared healthy, and were fertile. Peritoneal macrophages from ICE-deficient mice underwent apoptosis normally upon ATP treatment. Thymocytes from young ICE-deficient mice also underwent apoptosis when triggered by dexamethasone, gamma irradiation, or aging. ICE-deficient mice had a major defect in the production of mature IL-1β and had impaired IL-1α production on LPS stimulation in vitro and in vivo. ICE-deficient mice were resistant to LPS-induced endotoxic shock. J. Cell. Biochem. 64:27–32. © 1997 Wiley-Liss, Inc.     

Altered stress responsiveness and hypothalamic‐pituitary‐adrenal axis function in male rat offspring of socially isolated parents

Social isolation in male rats at weaning results in reduced basal levels of the neuroactive steroid 3α,5α‐tetrahydroprogesterone (3α,5α‐TH PROG) in the brain and plasma as well as increased anxiety‐like behavior. We now show that socially isolated female rats also manifest a reduced basal cerebrocortical concentration of 3α,5α‐TH PROG as well as an anxiety‐like profile in the elevated plus‐maze and Vogel conflict tests compared with group‐housed controls. In contrast, despite the fact that they were raised under normal conditions, adult male offspring of male and female rats subjected to social isolation before mating exhibited an increased basal cerebrocortical level of 3α,5α‐TH PROG but no difference in emotional reactivity compared with the offspring of group‐housed parents. These animals also showed an increased basal activity of the hypothalamic‐pituitary‐adrenal axis as well as reduced abundance of corticotropin‐releasing factor in the hypothalamus and of corticotropin‐releasing factor receptor type 1 in the pituitary. Moreover, negative feedback regulation of hypothalamic‐pituitary‐adrenal axis activity by glucocorticoid was enhanced in association with up‐regulation of glucocorticoid receptor expression in the hippocampus. There was also attenuation of corticosterone release induced by foot‐shock stress in the offspring of socially isolated parents. The increase in the brain concentration of 3α,5α‐TH PROG induced by acute stress was also blunted in these animals. Our results thus show that a stressful experience before mating can influence neuroendocrine signaling in the next generation.     

Effects of endocrine disrupters on sex steroid synthesis and metabolism pathways in fish

The interactions of estrogenic (nonylphenol, dicofol, atrazine), androgenic (organotins, phthalates, fenarimol) and anti-androgenic compounds (vinclozolin, diuron, p,p'-DDE) with key enzymatic activities involved in both synthesis and metabolism of sex hormones was investigated. Carp testicular microsomes incubated in the presence of androstenedione and different xenobiotics evidenced higher sensitivity of 5alpha-reductase activity than 17beta-hydroxysteroid dehydrogenase activity towards those chemicals. Dicofol, organotins and phthalates were among the most effective inhibitors. In contrast, ovarian synthesis of maturation-inducing hormones (20alpha- and 20beta-hydroxysteroid dehydrogenase activities) were enhanced by nonylphenol, dicofol, fenarimol and p,p'-DDE. Metabolic clearance pathways of hormones were also affected. Fenarimol, nonylphenol and triphenyltin inhibited the glucuronidation of testosterone and estradiol at concentrations as low as 10, 50 and 100 microM, respectively. Triphenyltin, tributyltin and nonylphenol were also inhibitors of estradiol sulfation with IC(50) values of 17, 18 and 41 microM. Overall, the data indicates the interaction of selected chemicals with key enzymatic pathways involved in both synthesis and metabolism of sex hormones. This interference might be one of the underlying mechanisms for the reported hormonal disrupting properties of the tested compounds, and might finally affect physiological processes such as gamete growth and maturation.     

Reverse structure of carnosine-induced sedative and hypnotic effects in the chick under acute stress

In the central nervous system, beta-alanine is thought to act as an inhibitory neurotransmitter, but the role or precise mechanism of beta-alanine in the brain has not been clearly defined. beta-Alanine is found in high levels in the chicken brain as a component of the dipeptides carnosine (beta-alanyl-L-histidine) and anserine, or as a free amino acid. We focused on the position of beta-alanine, i.e., at the carboxyl terminus. In Experiment 1, the central effects of glycyl-beta-alanine, L-histidyl-beta-alanine and L-valyl-beta-alanine were compared with a saline control in chicks. L-Histidyl-beta-alanine significantly induced sedative and hypnotic effects. In Experiment 2, the effects of carnosine, its reverse (L-histidyl-beta-alanine), and their combination were investigated. Central carnosine-induced hyperactivity while reverse carnosine-induced hypoactivity, and the behaviors were intermediate following the combination of the two peptides. Finally, the central effect of reverse carnosine was compared with beta-alanine alone and L-seryl-beta-alanine in Experiment 3. Reverse carnosine showed similar effects to beta-alanine. In conclusion, L-histidyl-beta-alanine not only has the reverse structure of carnosine, but also reverse function. Thus, we propose to name reverse carnosine (L-histidyl-beta-alanine) rev-carnosine.     

17α-Ethyl-5β-estrane-3α,17β-diol, a biological marker for the abuse of norethandrolone and ethylestrenol in slaughter cattle

The metabolism of the illegal growth promoter ethylestrenol (EES) was evaluated in bovine liver cells and subcellular fractions of bovine liver preparations. Incubations with bovine microsomal preparations revealed that EES is extensively biotransformed into norethandrolone (NE), another illegal growth promoter. Furthermore, incubations of monolayer cultures of hepatocytes with NE indicated that NE itself is rapidly reduced to 17α-ethyl-5β-estrane-3α,17β-diol (EED). In vivo tests confirmed that, after administration of either EES or NE, EED is excreted as a major metabolite. Therefore, it was concluded that, both in urine and faeces samples, EED can be used as a biological marker for the illegal use of EES and/or NE. Moreover, by monitoring EED in urine or faeces samples, the detection period after NE administration is significantly prolonged. These findings were further confirmed by three cases of norethandrolone abuse in a routine screening program for forbidden growth promoters.     

5-azacytidine alters TGF-beta and BMP signaling and induces maturation in articular chondrocytes

Maintenance of the articular surface depends on the function of articular chondrocytes (ACs) which produce matrix and are constrained from undergoing the maturation program seen in growth plate chondrocytes. Only during pathologic conditions, such as in osteoarthritis, are maturational constraints lost causing recapitulation of the process that occurs during endochondral ossification. With the aim of establishing a model to identify regulatory mechanisms that suppress AC hypertrophy, we examined the capability of 5-azacytidine (Aza) to have an impact on the maturational program of these cells. Primary ACs do not spontaneously express markers of maturation and are refractory to treatment by factors that normally regulate chondrocyte maturation. However, following exposure to Aza, ACs (i) were induced to express type X collagen (colX), Indian hedgehog, and alkaline phosphatase and (ii) showed altered colX and AP expression in response to bone morphogenetic protein-2 (BMP-2), transforming growth factor-beta (TGF-beta), and parathyroid hormone-related protein (PTHrP). Since Aza unmasked responsiveness of ACs to BMP-2 and TGF-beta, we examined the effect of Aza treatment on signaling via these pathways by assessing the expression of the TGF-beta Smads (2 and 3), the BMP-2 Smads (1 and 5), and the Smad2 and 3-degrading ubiquitin E3 ligase Smurf2. Aza-treated ACs displayed less Smad2 and 3 and increased Smad1, 5, and Smurf2 protein and showed a loss of TGF-beta signaling on the P3TP-luciferase reporter. Suggesting that Aza-induction of Smurf2 may be responsible for the loss of Smad2 and 3 protein via this pathway, immunoprecipitation and metabolic labeling experiments confirmed that Aza accelerated the ubiquitination and degradation of these targets. Overall, Aza-treated ACs represent a novel model for the study of mechanisms that regulate maturational potential of articular cartilage, with the data suggesting that maturation of these cells may be due to up-regulation of Smad1 and 5 coupled with a Smurf2-dependent degradation of Smad2 and 3 and loss of TGF-beta signaling.     

Irisin reverses intestinal epithelial barrier dysfunction during intestinal injury via binding to the integrin αVβ5 receptor

Disruption of the gut barrier results in severe clinical outcomes with no specific treatment. Metabolic disorders and destruction of enterocytes play key roles in gut barrier dysfunction. Irisin is a newly identified exercise hormone that regulates energy metabolism. However, the effect of irisin on gut barrier function remains unknown. The therapeutic effect of irisin on gut barrier dysfunction was evaluated in gut ischemia reperfusion (IR). The direct effect of irisin on gut barrier function was studied in Caco‐2 cells. Here, we discovered that serum and gut irisin levels were decreased during gut IR and that treatment with exogenous irisin restored gut barrier function after gut IR in mice. Meanwhile, irisin decreased oxidative stress, calcium influx and endoplasmic reticulum (ER) stress after gut IR. Moreover, irisin protected mitochondrial function and reduced enterocyte apoptosis. The neutralizing antibody against irisin significantly aggravated gut injury, oxidative stress and enterocyte apoptosis after gut IR. Further studies revealed that irisin activated the AMPK‐UCP 2 pathway via binding to the integrin αVβ5 receptor. Inhibition of integrin αVβ5, AMPK or UCP 2 abolished the protective role of irisin in gut barrier function. In conclusion, exogenous irisin restores gut barrier function after gut IR via the integrin αVβ5‐AMPK‐UCP 2 pathway.