Collagen type I prevents glyoxal-induced apoptosis in osteoblastic cells cultured on titanium alloy

Advanced glycation end products (AGEs) irreversibly cross-link proteins with sugars and accumulate at a higher age and in diabetes, processes which can interfere with the integration of implants into the tissue. Glyoxal is a highly reactive glycating agent involved in the formation of AGEs and is known to induce apoptosis, as revealed by the upregulation of caspase-3 and fractin (caspase-3 being a key enzyme activated during the late stage of apoptosis and fractin being a caspase-cleaved actin fragment). In this study, we investigated the influence of collagen type I coating on the cytotoxic effect of glyoxal on rat calvarial osteoblastic cells and on human osteosarcoma cells (Saos-2) grown on titanium alloy, Ti6Al4V. Activation of caspase-3 and fractin was measured by counting immunohistochemically stained cells and by flow cytometry with propidium iodide (detection of the apoptosis indicating a sub-G1 peak). Our results showed an increased number of apoptotic osteoblasts after incubation with glyoxal on Ti6Al4V discs. However, the number of apoptotic cells on collagen-coated titanium was significantly smaller than on uncoated titanium after the same treatment. The present findings demonstrate that osteoblasts treated with glyoxal undergo apoptosis, whereas collagen type I coating of titanium alloys (used for implants) has an antiapoptotic function.     

Advanced glycation end products induce T cell apoptosis: Involvement of oxidative stress, caspase and the mitochondrial pathway

Accumulation of advanced glycation end products (AGEs) is a hallmark in aged people. T cells play important roles in maintaining homeostasis of immune function. This study investigated the effects of AGEs-bovine serum albumin (AGEs) in human T cells. Incubation of Jurkat and several immortalized T cell lines with AGEs resulted in cell death dose-dependently. AGEs-induced cell death was partially but significantly blocked by neutralizing antibodies recognizing receptor of AGEs. In addition to detecting DNA nick, simultaneous stainings of annexin V with 7-amino-actinomycin D further confirmed the apoptotic nature of cell death. AGEs also caused apoptosis in purified T cells. Although AGEs-induced apoptosis could be blocked by the pan-caspase inhibitor, Ala-Asp-fluomethyl ketone (Z-VAD-fmk), there was no activation of caspase-3, -5, -8 and -9. AGEs caused mitochondrial outer membrane permeabilization and this process was prevented by an antioxidant or Z-VAD-fmk. Furthermore, AGEs treatment led to translocation of apoptosis inducing factor (AIF) from the mitochondria into the nucleus. Altogether, this report demonstrated that AGEs induced T cell apoptosis in an oxidative stress-associated and caspase-dependent manner with involvement of the mitochondrial pathway. It is likely that AGEs-induced T cell apoptosis may play a role in T cell homeostasis in ageing.     

氨基胍对D-半乳糖致大鼠眼晶状体损伤的影响及其机制

目的： 探讨D-半乳糖致大鼠眼晶体损伤及氨基胍的干预作用及其机制。方法： D-半乳糖（400 mg·kg-1）腹腔注射给药,2周后模型大鼠给予氨基胍（AG）高剂量（150 mg·kg-1）和低剂量（75 mg·kg-1）处理至第14周。处理动物并取血测定红细胞醛糖还原酶（AR）活性、糖化血红蛋白、血清果糖胺(FRA)和晚期糖基化终末产物(AGEs)含量;取眼晶状体测定AR、GR、SOD和SDH活性,测定AGEs、 GSH、MDA含量和乳酸脱氢酶（LDH）漏出量,流式细胞术检测晶状体上皮细胞凋亡情况,透射电镜观察晶状体上皮细胞超微结构的变化。结果： D-半乳糖处理动物14周后,体内糖化血红蛋白、血清果糖胺、AGEs水平和AR活性明显升高,并伴有眼晶状体AGEs含量和AR活性的增加,抗氧化酶活性降低,氧化产物增加,晶状体上皮细胞出现凋亡及细胞核和线粒体结构的损伤。氨基胍处理12周后,明显降低动物体内红细胞和晶状体AR活性（P<0.01）,降低糖化血红蛋白、血清果糖胺和AGEs含量,降低晶状体AGEs、MDA含量（P<0.01）和LDH释放量（P<0.05）,提高GR、SDH和SOD活性（P<0.05或P<0.01）,并降低晶状体上皮细胞凋亡率（P<0.05或P<0.01）,减少细胞核和线粒体的损伤程度。结论： 氨基胍对D-半乳糖致大鼠全身和眼晶状体糖基化和氧化应激性损伤具有抑制作用,并减缓其对眼晶状体上皮细胞核和线粒体结构的损伤,抑制细胞凋亡的发生。     

自噬在晚期糖基化终产物诱导的内皮细胞凋亡中的作用

目的: 研究晚期糖基化终产物(AGEs)对人脐静脉内皮细胞(HUVECs)自噬水平的影响并探讨自噬在AGEs诱导的内皮细胞凋亡中的作用。方法: 用AGEs处理HUVECs,相同条件牛血清白蛋白处理为对照组,Western blotting检测相应蛋白表达的变化,电镜观察细胞自噬体的出现,流式细胞术检测细胞凋亡,MTT比色法测定细胞活性。结果: AGEs处理HUVECs后,自噬相关蛋白LC3-Ⅱ的表达显著上调并呈时间和浓度依赖性,电镜观察到细胞胞浆内自噬体数量增加;与对照组比较,AGEs处理组内皮细胞凋亡率增加,活性下降,自噬抑制剂3-甲基腺嘌呤预处理的AGEs组细胞活性较AGEs组进一步下降,凋亡率继续增加。AGEs处理HUVECs后,蛋白激酶B(Akt)和哺乳动物雷帕霉素靶蛋白(mTOR)的磷酸化水平也明显下调, Akt激活剂胰岛素样生长因子1预处理后,Akt的磷酸化水平增加,自噬相关蛋白LC3-Ⅱ的增高表达被抑制。结论: AGEs通过PI3K/Akt/mTOR介导的信号通路诱导HUVECs自噬水平升高。自噬在AGEs诱导的内皮细胞凋亡中对细胞起保护作用。     

Oxidative stress and protein glycation in diabetes mellitus

Metabolic alterations of diabetes mellitus are not only informative biological signs, but also factors of degenerative complications. Thus, hyperglycaemia increases non enzymatic glycation, characterized by the binding of simple oses (glucose) or by-products to amino groups of proteins. This reaction leads to the formation of complex compounds, advanced glycation end products (AGEs), which alter structure and functions of proteins. Glycation and oxidative stress are closely linked, and both phenomena are referred to as "glycoxidation". All steps of glycoxidation generate oxygen free radical production, some of them being common with lipidic peroxidation pathways. Besides, glycated proteins activate membrane receptors such as RAGE through AGEs, and induce an intracellular oxidative stress and a pro-inflammatory status. So, glycated proteins may modulate functions of cells involved in oxidative metabolism and induce inappropriate responses. Finally, some oxidative products (reactive aldehydes such as methylglyoxal) or lipid peroxidation products (malondialdehyde) may bind to proteins and amplify glycoxidation-generated lesions. The knowledge of glycoxidation mechanisms may lead to new therapeutic approaches.     

晚期糖基化终末产物通过氧化应激诱导大鼠软骨细胞损伤

目的:探讨晚期糖基化终末产物(advanced glycation end products,AGEs)能否通过氧化应激引起大鼠软骨细胞损伤。方法:原代培养SD大鼠软骨细胞,对细胞表型进行鉴定;应用CCK-8法检测软骨细胞生存率;DCFH-DA染色荧光显微镜下检测胞内活性氧簇(reactive oxygen species,ROS)的水平;Hoechst 33342核染色法及Annexin V-FITC/PI流式细胞法测定软骨细胞的凋亡率;RT-PCR法检测软骨细胞中Bax、Bcl-2、caspase-3、MMP3、MMP13和COL2的mRNA水平;Western blotting法检测软骨细胞中cleaved caspase-3、MMP3、MMP13和COL2的蛋白水平。结果:与对照组相比,AGEs可显著上调胞内ROS水平(P0.05),但经抗氧化剂N-乙酰半胱氨酸(NAC)抑制后ROS的生成明显减少(P0.05);另外,NAC可抑制AGEs引起的软骨细胞凋亡相关分子Bax/Bcl-2和caspase-3水平的上调,并减少MMP3和MMP13表达及COL2的丢失(P0.05)。结论:AGEs可通过氧化应激诱导大鼠软骨细胞损伤。     

糖基化终产物与糖尿病血管并发症

糖尿病时糖基化终产物(advanced glycation end products,AGEs)生成与蓄积不仅加速糖尿病本身的发展,还与糖尿病肾病、视网膜病、神经性疾病和心血管疾病等慢性并发症密切相关。AGEs与糖基化终产物受体(receptor for advanced glycation end products,RAGE)相互作用诱导氧化应激,促进炎症反应,影响凝血系统,在糖尿病及其并发症的病理生理过程中起重要作用。抑制AGEs生成、交联结构及阻断AGEs与RAGE相互作用为寻找治疗糖尿病血管并发症的药物提供了新的途径。     

Hepatic expression of galectin-3 and receptor for advanced glycation end products in patients with liver disease

BACKGROUND: Advanced glycation end products (AGEs) are a heterogeneous group of glycosylated proteins (of which carboxymethyl-lysine (CML) is the most common) which accumulate during ageing processes and play an important role in the pathogenesis of a variety of chronic diseases. Impaired hepatic function might result in elevated levels of AGEs, as the liver represents the major site of AGE metabolism. The actions of AGEs are mediated by various receptors, among which the AGE-receptor complex (including galectin-3 as an essential part) is thought to have a cytoprotective effect, and receptor for advanced glycation end product (RAGE) a cytotoxic effect. AIM: To assess the relationship between CML and expression of galectin-3 and RAGE in different histological structures in biopsy specimens from patients with varying degrees of liver impairment. METHOD: Immunohistochemical staining of 164 biopsies from patients with varying degrees of liver impairment was performed to determine the levels of CML, galectin-3 and RAGE in hepatocytes, Kupffer cells and bile ducts by a semiquantative score. RESULTS: Independent of diagnosis, CML and RAGEs were detected in hepatocytes, whereas galectin-3 was present only in hepatocytes of cirrhotics. By contrast, CML and galectin-3 were highly expressed in Kupffer cells (well correlating levels, highest scores in cholestasis) whereas expression of RAGEs was not significant. All three assessed biochemical markers showed their highest levels of expression/detection in bile ducts. CONCLUSION: These findings indicate an increased susceptibility of hepatocytes to the detrimental effects of AGEs and underline the protective function of Kupffer cells. Furthermore, the biliary system seems to play an important role in the disposition of AGEs.     

晚期糖基化终末产物诱导人卵巢颗粒细胞株COV434凋亡并上调促炎因子HMGB1自分泌

目的:探讨晚期糖基化终末产物(advanced glycation end products,AGEs)是否诱导人卵巢颗粒细胞株COV434凋亡,并探究其可能的机制。方法:采用不同浓度AGEs牛血清白蛋白与人卵巢颗粒细胞株COV434共同孵育,流式细胞术观察细胞凋亡率,Western blot观察caspase-3和cleaved caspase-3的蛋白水平,ELISA检测细胞培养液上清中高迁移率族蛋白B1(high mobility group box 1 protein,HMGB1)的含量。结果:与对照组比较,100 mg/L AGEs组和200 mg/L AGEs组早、晚期凋亡率显著增加,各组caspase-3蛋白水平的差异无统计学显著性,但与对照组比较,100 mg/L AGEs组和200 mg/L AGEs组cleaved caspase-3的蛋白水平显著增加(P0.05)。此外,与对照组比较,100 mg/L AGEs组和200 mg/L AGEs组细胞培养液上清中HMGB1促炎介质的水平显著上升(P0.05)。结论:晚期糖基化终末产物诱导人卵巢颗粒细胞株COV434凋亡可能与促炎反应有关。     

The induction of surface β-amyloid binding proteins and enhanced cytotoxicity in cultured PC-12 and IMR-32 cells by advanced glycation end products

During aging the non-enzymatic glycation of proteins and other molecules increases significantly, leading to the accumulation of advanced glycation end-products (AGEs). These AGEs enhance inflammatory and autoimmune reactions with resultant cytotoxicity. We noted in an earlier study that individuals with Alzheimer’s disease exhibit enhanced expression of the receptor for advanced glycation end-products (RAGE) on the surface of their leukocytes. In order to better understand the relationship between AGEs and the cell surface binding of amyloid-β protein (Aβ) 42 we studied the effect of two AGEs: glycated bovine serum albumin (BSA), and ε-carboxymethyllysine-BSA (CML), a glycoxidation product, on the binding of Aβ42 to rat PC-12 and IMR-32 cells. We measured the expression of three potential cell surface receptors binding Aβ42: RAGE, β-amyloid precursor protein (β-APP), and the α7 subtype of the nicotinic acetylcholine receptor (α7nAChR) by using specific antibody probes. Incubation of PC-12 or IMR-32 cells with bovine serum albumin–advanced glycation end-product (BSA-AGE) or with CML induced small but significant concentration-dependent increases in the expression of β-APP, RAGE, and α7nAChRs as measured by flow cytometry or by ELISA. Incubation of the cells with 48 μM of either of the AGEs combined with varying concentrations (138–1100 nM) of Aβ42 resulted in the enhanced binding of the Aβ42 to the cell surface as compared with cells not exposed to the AGE co-treatment. The combination of AGE and Aβ treatment also resulted in the heightened expression of all three potential Aβ binding sites as well as their gene precursors. Exposure of cells to the same regimen of AGE plus Aβ resulted in the production of reactive oxygen species and mitochondrial toxicity. These results are consistent with the ability of AGEs to enhance the cell surface expression of diverse Aβ42 binding sites, a factor that can lead to the enhanced binding of amyloid and subsequent cell death.     

梓醇抑制AGEs诱导的EA.hy926细胞炎症反应及RAGE表达

目的:研究梓醇对晚期糖基化终产物(AGEs)诱导的EA.hy926内皮细胞炎症反应的抑制作用并探讨其可能机制。方法:将常规培养的EA.hy926细胞随机分为对照组、梓醇对照组、AGEs组以及梓醇高剂量(0.5 mmol/L)、中剂量(0.25 mmol/L)和低剂量(0.05 mmol/L)保护组。激光共聚焦显微镜观察细胞内活性氧簇(ROS)的生成;RT-PCR和Western blot检测细胞中单核细胞趋化蛋白1(MCP-1)、肿瘤坏死因子α(TNF-α)、血管细胞黏附分子1(VCAM-1)及晚期糖基化终产物受体(RAGE)的mRNA及蛋白的表达。结果:梓醇保护组ROS生成均明显减少,MCP-1、TNF-α和VCAM-1的mRNA及蛋白表达均显著降低,RAGE蛋白表达明显受抑制,且呈剂量依赖性(P0.05)。结论:梓醇能够有效抑制AGEs诱导的EA.hy926细胞内氧化应激,减轻炎症反应,其机制可能与其降低RAGE表达有关。     

The receptor for advanced glycation end products and its ligands: a new inflammatory pathway in lung disease?

The binding of the receptor for advanced glycation end products (RAGE) with its ligands begins a sustained period of cellular activation and inflammatory signal amplification in different tissues and diseases. This binding could represent an as yet uninvestigated pathway of inflammatory reaction in the lung, where the presence of the receptor has been largely documented and advanced glycation end products (AGEs) are produced by nonenzymatic glycation and oxidation of proteins and lipids, driven by smoke and pollutants exposure or inflammatory stress. We immunohistochemically assessed the expression of RAGE and of its major proinflammatory ligands, N-epsilon-carboxy-methyl-lysine, S100B and S-100A12 in normal lung and in non-neoplastic lung disorders including smoke-related airway disease, granulomatous inflammation, postobstructive damage and usual interstitial pneumonia. In normal lung low expression of the receptor was observed in bronchiolar epithelia, type II pneumocytes, macrophages and some endothelia. S100A12 and S100B were expressed, respectively, in granulocytes and in dendritic cells. Carboxy-methyl-lysine was present in bronchiolar epithelia and macrophages. In all pathological conditions associated with inflammation and lung damage overexpression of both the receptor and of AGEs was observed in bronchiolar epithelia, type II alveolar pneumocytes, alveolar macrophages and endothelia. RAGE overexpression was more evident in epithelia associated with inflammatory cell aggregates. Fibroblasts in usual interstitial pneumonia expressed both the receptor and AGEs. The number of S100A12 and S100B immunoreactive inflammatory cells was variable. S100A12 was also expressed in mononuclear inflammatory cells and in activated epithelia. The activation of the inflammatory pathway controlled by the RAGE is not specific of a single lung disease, however, it may be relevant as a nonspecific pathway of sustained inflammation in lung tissue, and on this basis therapeutic approaches based on receptor blockage can be envisaged.     

Advanced glycation end products accelerate ischemia/reperfusion injury through receptor of advanced end product/nitrative thioredoxin inactivation in cardiac microvascular endothelial cells

The advanced glycation end products (AGEs) are associated with increased cardiac endothelial injury. However, no causative link has been established between increased AGEs and enhanced endothelial injury after ischemia/reperfusion. More importantly, the molecular mechanisms by which AGEs may increase endothelial injury remain unknown. Adult rat cardiac microvascular endothelial cells (CMECs) were isolated and incubated with AGE-modified bovine serum albumin (BSA) or BSA. After AGE-BSA or BSA preculture, CMECs were subjected to simulated ischemia (SI)/reperfusion (R). AGE-BSA increased SI/R injury as evidenced by enhanced lactate dehydrogenase release and caspase-3 activity. Moreover, AGE-BSA significantly increased SI/R-induced oxidative/nitrative stress in CMECs (as measured by increased inducible nitric oxide synthase expression, total nitric oxide production, superoxide generation, and peroxynitrite formation) and increased SI/R-induced nitrative inactivation of thioredoxin-1 (Trx-1), an essential cytoprotective molecule. Supplementation of EUK134 (peroxynitrite decomposition catalyst), human Trx-1, or soluble receptor of advanced end product (sRAGE) (a RAGE decoy) in AGE-BSA precultured cells attenuated SI/R-induced oxidative/nitrative stress, reduced SI/R-induced Trx-1 nitration, preserved Trx-1 activity, and reduced SI/R injury. Our results demonstrated that AGEs may increase SI/R-induced endothelial injury by increasing oxidative/nitrative injury and subsequent nitrative inactivation of Trx-1. Interventions blocking RAGE signaling or restoring Trx activity may be novel therapies to mitigate endothelial ischemia/reperfusion injury in the diabetic population.     

球状脂联素上调脂联素受体1抑制晚期糖基化终产物诱导人脐静脉内皮细胞凋亡的初步研究

目的:观察球状脂联素(gAd)对晚期糖基化终产物(AGEs)诱导人脐静脉内皮细胞(HUVECs)凋亡时脂联素受体1(AdipoR1)表达的影响。方法:体外培养HUVECs,用不同浓度AGEs作用HUVECs,以及预处理gAd后再联合AGEs作用HUVECs。MTT比色法测定细胞活性、Annexin V-FITC/PI双染标记流式细胞仪检测细胞凋亡、实时定量RT-PCR检测内皮细胞AdipoR1 mRNA的表达。结果:AGEs作用HUVECs,细胞凋亡具有AGEs浓度依赖性(P0.05)。相同浓度AGEs作用HUVECs,有和无gAd预处理的2组比较,用gAd预处理组明显拮抗HUVECs凋亡(P0.01)。实时定量RT-PCR检测发现,gAd具有上调AdipoR1 mRNA表达的作用,与相同浓度AGEs作用的无gAd预处理组比较,差异显著(P0.01)。结论:gAd可能通过上调AdipoR1表达拮抗AGEs诱导HUVECs的凋亡。     

Immunochemical crossreactivity of antibodies specific for "advanced glycation endproducts" with "advanced lipoxidation endproducts"

Antibodies against advanced glycation endproducts (AGEs) are used for their immunohistological localization in tissues, for example in Alzheimer's disease (AD) or diabetes. Many monoclonal and polyclonal antibodies have been used, and their specificity is unknown in most cases. Increased radical production, leading to the formation of lipid-derived reactive carbonyl species, such as malondialdehyde (MDA), acrolein, and glyoxal, is a characteristic aspect of age-related diseases like Alzheimer's disease or diabetic polyneuropathy. These reactive carbonyl species are able to modify proteins, resulting in AGE related structures, termed "advanced lipoxidation products" (ALEs). In this study, the monoclonal carboxymethyllysine-specific antibody 4G9 and the polyclonal AGE-antibody K2189 were tested for their immunoreactivity towards these carbonyl-derived protein modifications. To investigate which carbonyl-modified amino acid side chains are specifically recognized by these antibodies, peptide membranes were incubated with glyoxal, MDA and acrolein. As model proteins, microtubuli associated protein tau (MAP-tau), beta-amyloid, human serum albumin and chicken egg albumin were incubated likewise. It was found that both antibodies detected reaction products of these carbonyl compounds on lysine- and arginine residues and for the protein modification, it was found that some epitopes might not be detected. In conclusion, AGE-antibodies might not only detect sugar-derived AGEs but also structures derived from lipid peroxidation products (serving as markers of oxidative stress).     

Life and death decisions: ceramide generation and EGF receptor trafficking are modulated by oxidative stress

Reactive oxidants are associated with the pathogenesis of pulmonary diseases and affect various cell functions, from proliferation to apoptosis. We have shown that oxidants exert growth control on airway epithelial cells by modulating upstream receptor function. Additionally, hydrogen peroxide-mediated oxidative stress modulates ceramide levels to induce apoptosis in lung epithelium. Depletion of glutathione in lung epithelial cells results in ceramide accumulation, suggesting that ceramide elevation, coupled to oxidative stress, initiates apoptosis. While it is desirable to prevent cell death and tissue injury induced by oxidants in diseases such as asthma or acute respiratory distress syndrome, the opposite is sought in cancer. But oxidants may also activate growth factor receptors, enhancing cell proliferation and facilitating tumor promotion. Under oxidative stress, phosphorylation of the epidermal growth factor receptor (EGFR) is abrogated at tyrosine 1,045, the docking site for the ubiquitin ligase c-Cbl, rendering EGFR unable to recruit c-Cbl and be ubiquitylated and degraded. We thus proposed that this deficiency, which confers prolonged receptor signaling at the plasma membrane, links oxidative stress, EGFR, and tumorigenesis. Decoding the molecular interactions between oxidative stress and ceramide pathways and characterizing ubiquitylation control of receptor desensitization should provide new strategies for intervention in diverse pulmonary diseases and in diagnosing and eradicating cancer.     

Effect of acrylamide on BEAS-2B normal human lung cells: Cytotoxic,oxidative, apoptotic and morphometric analysis

Due to the broad toxic relevance of acrylamide, many measures have been taken since the 1900s. These measures increased day by day when acrylamide was discovered in foods in 2002, and its toxic spectrum was found to be wider than expected. Therefore, in some countries, the products with higher acrylamide content were restricted. On the other hand, the effects of acrylamide on the respiratory system cells have yet to be well understood. In this study, we aimed at investigating the effect of acrylamide on lung epithelial BEAS-2B cells. Initially, the cytotoxic effect of acrylamide on BEAS-2B was determined by MTT assay. Then, cellular oxidative stress was measured. Flow cytometry analysis was conducted for Annexin-V and caspase 3/7. Furthermore, Bax, Bcl-2 and Nrf-2 proteins were evaluated by immunocytochemistry. Finally, acrylamide-induced cellular morphological changes were observed under confocal and TEM microscopes. According to MTT results, the IC50 concentration of acrylamide was 2.00 mM. After acrylamide treatment, oxidative stress increased dose-dependently. Annexin V-labelled apoptotic cells and caspase 3/7 activity were higher than untreated cells in acrylamide-treated cells. Immunocytochemical examination revealed a marked decrease in Bcl-2, an increase in Bax and Nrf-2 protein staining upon acrylamide treatment. Furthermore, in confocal and TEM microscopy, apoptotic hallmarks were pronounced. In the present study, acrylamide was suggested to display anti-proliferative activity, decrease viability, induce apoptosis and oxidative stress and cause morphological changes in BEAS-2B cells.     

Epithelial cell apoptosis by fas ligand-positive myofibroblasts in lung fibrosis

The Fas/Fas ligand (FasL) apoptotic pathway has been shown to be involved in bleomycin-induced lung fibrosis. We examined the hypothesis that myofibroblasts from fibrotic lungs possess a cytotoxic phenotype that causes apoptosis of epithelial cells via the Fas/FasL pathway. We show in vivo epithelial cell apoptosis and associated upregulation of Fas and apoptotic Fas pathway genes in epithelial cells of lungs with bleomycin-induced fibrosis. In addition, we show that FasL surface molecules are overexpressed on alpha-SMA-positive cells in mice with bleomycin-induced fibrosis, and in humans with idiopathic pulmonary fibrosis. This enables the molecules to kill Fas-positive epithelial cells. In contrast, FasL-deficient myofibroblasts lose this myofibroblast cytotoxic phenotype, both in vivo and in vitro. In vivo, there was no bleomycin-induced epithelial cell apoptosis, as assessed by specific M30 staining in chimeric FasL-deficient mice that lacked FasL-positive myofibroblasts. In vitro, FasL-positive, but not FasL-negative myofibroblasts, induce mouse lung epithelial cell apoptosis. Thus myofibroblast cytotoxicity may underlie the absence of re-epithelialization, resulting in persistent lung fibrosis.     

Conversion of Amadori products of the Maillard reaction to N(epsilon)-(carboxymethyl)lysine by short-term heating: possible detection of artifacts by immunohistochemistry

Accumulation of advanced glycation end products (AGE) of the Maillard reaction increases by aging and in age-enhanced diseases such as atherosclerosis and diabetic complications. Immunohistochemical analysis has been used to demonstrate AGE in vivo. In immunochemistry, the heat-induced epitope retrieval technique is extensively used with formalin-fixed, paraffin-embedded tissue sections. Here we examined whether AGE could be formed artificially through the heating process. Normal rat skin and liver samples were divided into two groups, one rapidly frozen, the other formalin-fixed, paraffin-embedded and submitted to heat-induced epitope retrieval treatment. In heat-treated sections, the cytoplasm of rat epidermal cells and hepatocytes were strongly stained by monoclonal antibody against N(epsilon)-(carboxymethyl)lysine (CML), while the staining was negligible in either frozen sections or in paraffin-embedded but heat-untreated sections. To clarify the mechanism, we conducted heat treatment to glycated human serum albumin (HSA), a model Amadori protein, and generation of CML was determined by immunochemical and HPLC analysis. CML was generated from glycated HSA by heat treatment (above 80 degrees C) and increased in a time-dependent manner. In contrast, generation of CML from glycated HSA was significantly inhibited in the presence of NaBH4, a reducing agent, diethylenetriamine pentaacetic acid, a chelator of transition metal ion, or aminoguanidine, a trapping reagent for alpha-oxoaldehydes. Furthermore, heat-induced CML formation in rat liver samples determined by HPLC was markedly reduced by pretreatment with NaBH4. Reactive intermediates such as glucosone, 3-deoxyglucosone, methylglyoxal, and glyoxal were formed upon heat treatment of glycated HSA at 100 degrees C, indicating that these aldehydes generated from Amadori products by oxidative cleavage can contribute to further CML formation. CML generated by heating, directly from Amadori products or via these aldehydes, might serve as an artifact upon immunohistochemistry.