The Adverse Effects of Se Toxicity on Inflammatory and Immune Responses in Chicken Spleens

Selenium (Se) is an essential trace element, but excessive intake of Se could induce Se poisoning, and result in various health problems. NF-κB regulated many molecules of the immune response and the inflammatory response, and Th1/Th2 balance played a key in the regulation of immune response. The aim of this study is to investigate the role of NF-κB pathway and Th1/Th2 imbalance in the adverse influence of Se poisoning on chicken spleens. In the current study, 90 chickens were randomly divided into two groups (n?=?45 per group). The chickens were maintained either on a basal diet (the control group) containing 0.2 mg/kg Se or a high supplemented diet (the Se group) containing 15 mg/kg Se for 45 days. Then, we observed the pathohistology of spleen cells and detected NO content, iNOS activity, and the expression of NF-κB, iNOS, COX-2, PTGE, IL-6, TNF-α, Foxp3, IL-4, and IFN-γ in chicken spleens. In chicken spleens of the Se group, the result showed typical characteristics of inflammation: the content of NO and the activity of iNOS were increased, and the expression of NF-κB, iNOS, COX-2, PTGE, IL-6, TNF-α, and IL-4 was enhanced and that of Foxp3 and IFN-γ was decreased. Our study showed that Se toxicity could promote inflammation via NF-κB pathway, impairing the immune function, and changing Th1/Th2 balance in the chicken spleens.     

Gene expression of selenoproteins can be regulated by selenoprotein K silencing in chicken myoblasts

The aim of the present study was to clarify the effect of Selenoprotein K (Selk) silencing on the mRNA expression of 25 selenoproteins in chicken myoblasts. The specific small interfering RNA (siRNA) for Selk gene was designed and transfected into chicken myoblasts. Post-transfection mRNA expression of 25 selenoproteins was determined at various time periods i.e., 24, 48 and 72 h. Moreover, based on the results of expression of 25 selenoproteins, correlation analysis and principal component analysis (PCA) were used for further analysis. The results showed that the designed siRNA effectively inhibited Selk expression (decreased by 20, 29 and 43 % on 24, 48 and 72 h, respectively) and the mRNA expression levels of the 23 selenoproteins were influenced by silencing Selk differently (P < 0.05). Time-dependent pattern of mRNA expression after siRNA treatment in three groups were found similar: one group including Gpx1, Gpx2, Gpx3, Gpx4, Txnrd1, Txnrd2, Txnrd3, Sepw1, Selh, Sepp1, Selo and Sepx1, another group including Sepn1, Sels, Selt, Selm and Sep15 and other group including Dio2 and Dio3. The results of correlation analysis showed that Gpx1, Gpx2, Gpx3, Gpx4, Dio1, Dio3, Sepn1, Sels, Sepw1, Selt, Selh, Sep15, Seli and Selu had a positive correlation with Selk, while Dio2 and Sepp1 had a negative correlation with Selk. PCA data also indicated that Txnrd1, Txnrd2, Dio2, Selpb, Sepp1and Selo may play special roles in response to Selk silencing. In summary, these results indicated that different selenoproteins possess and exhibits distinct responses to silencing of Selk in chicken myoblasts.     

Selenium Deficiency Induced Injury in Chicken Muscular Stomach by Downregulating Selenoproteins

The aim of the present study was to examine the effect of selenium (Se) deficiency on the expression of selenoproteins in chicken muscular stomach and to detect the correlation of selenoproteins with muscular stomach injuries. One-day-old broiler chickens were maintained for 55 days on a normal diet (0.2 mg/kg) or a Se-deficient diet (0.033 mg Se/kg). The expression levels of 25 selenoproteins, heat shock proteins (HSPs), and inflammatory factors were then examined by real-time PCR. Following this, the correlation between selenoproteins, HSPs, and inflammatory factors was analyzed by principal component analysis (PCA). The results showed that Se deficiency decreased the expression of 25 selenoproteins (P < 0.05), but increased the expression of HSP27, HSP40, HSP60, HSP70, and HSP90, and NF-κB, iNOS, TNF-α, COX-2, and HO-1 (P < 0.05). Selenoproteins showed a high negative correlation with HSPs and inflammatory factors. Thus, the results suggested that Se deficiency induced muscular stomach injuries by decreasing the expression of selenoproteins. In addition, selenoproteins play an important role in regulating HSPs and inflammatory response. The muscular stomach is a key target of Se deficiency and may play a special role in response to Se deficiency.     

Suppression of NF-κB and NF-κB regulated oxidative stress and neuroinflammation by BAY 11-7082 (IκB phosphorylation inhibitor) in experimental diabetic neuropathy

Inflammation is an emerging patho-mechanism of diabetes and its complications. NF-κB pathway is one of the central machinery initiating and propagating inflammatory responses. The present study envisaged the involvement of NF-κB inflammatory cascade in the pathophysiology of diabetic neuropathy using BAY 11-7082, an IκB phosphorylation inhibitor. Streptozotocin was used to induce diabetes in Sprauge Dawley rats. BAY 11-7082 (1 &; 3 mg/kg) was administered to diabetic rats for 14 days starting from the end of six weeks post diabetic induction. Diabetic rats developed deficits in nerve functions and altered nociceptive parameters and also showed elevated expression of NF-κB (p65), IκB and p-IκB along with increased levels of IL-6 &; TNF-α and inducible enzymes (COX-2 and iNOS). Furthermore, there was an increase in oxidative stress and decrease in Nrf2/HO-1 expression. We observed that BAY 11-7082 alleviated abnormal sensory responses and deficits in nerve functions. BAY 11-7082 also ameliorated the increase in expression of NF-κB, IκB and p-IκB. BAY 11-7082 curbed down the levels of IL-6, TNF-α, COX-2 and iNOS in the sciatic nerve. Lowering of lipid peroxidation and improvement in GSH levels was also seen along with increased expression of Nrf2/HO-1. Thus it can be concluded that NF-κB expression and downstream expression of proinflammatory mediators are prominent features of nerve damage leading to inflammation and oxidative stress and BAY 11-7082 was able to ameliorate experimental diabetic neuropathy by modulating neuroinflammation and improving antioxidant defence.     

Anti-inflammatory activity of myricetin from Diospyros lotus through suppression of NF-κB and STAT1 activation and Nrf2-mediated HO-1 induction in lipopolysaccharide-stimulated RAW264.7 macrophages

Diospyros lotus is traditionally used for the treatment of diabetes, diarrhea, tumor, and hypertension. The purpose of this study was to investigate the anti-inflammatory effect and underlying molecular mechanisms of myricetin in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Myricetin dose-dependently suppressed the production of pro-inflammatory mediators (NO, iNOS, PGE₂, and COX-2) in LPS-stimulated RAW264.7 macrophages. Myricetin administration decreased the production of NO, iNOS, TNF-α, IL-6, and IL-12 in mice. Myricetin decreased NF-κB activation by suppressing the degradation of IκBα, nuclear translocation of p65 subunit of NF-κB, and NF-κB DNA binding activity in LPS-stimulated RAW264.7 macrophages. Moreover, myricetin attenuated the phosphorylation of STAT1 and the production of IFN-β in LPS-stimulated RAW264.7 macrophages. Furthermore, myricetin induced the expression of HO-1 through Nrf2 translocation. In conclusion, these results suggest that myricetin inhibits the production of pro-inflammatory mediators through the suppression of NF-κB and STAT1 activation and induction of Nrf2-mediated HO-1 expression in LPS-stimulated RAW264.7 macrophages.     

Naringenin Exerts Anti-inflammatory Effects in Paraquat-Treated SH-SY5Y Cells Through a Mechanism Associated with the Nrf2/HO-1 Axis

Naringenin (NGN; 5,7-dihydroxy-2-(4-hydroxyphenyl)-2,3-dihydrochromen-4-one; C₁₅H₁₂O₅), a flavanone, is found in citrus fruits and has been viewed as an antioxidant and anti-inflammatory agent. NGN is a potent inducer of the nuclear factor erythroid 2-related factor 2 (Nrf2) and upregulates the expression of heme oxygenase-1 (HO-1), an enzyme exhibiting both antioxidant and anti-inflammatory effects. The complete mechanism by which NGN exerts anti-inflammatory actions is not completely understood yet. Therefore, we investigated here whether NGN would be able to reduce the inflammation induced by paraquat (PQ) in SH-SY5Y cells. Additionally, we analyzed the mechanism associated with the NGN-induced anti-inflammatory effect. We found that a pretreatment with NGN at 80 µM for 2 h decreased the levels of pro-inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in PQ-treated SH-SY5Y cells. The production of nitric oxide (NO^·) and levels of cyclooxygenase-2 (COX-2) and of the inducible isoform of nitric oxide synthase (iNOS) were downregulated by NGN in the cells exposed to PQ. Moreover, NGN downregulated the activation of the nuclear factor-κB (NF-κB) in PQ-treated cells. The anti-apoptotic and anti-inflammatory effects promoted by NGN were abolished by ZnPP IX (a specific inhibitor of HO-1) or by knockdown of Nrf2 by small interfering RNA (siRNA). Therefore, NGN induced anti-inflammatory effects in PQ-treated SH-SY5Y cells by a mechanism associated with the Nrf2/HO-1 signaling pathway.     

Expression of HAb18G in non-small lung cancer and characterization of activation, migration, proliferation, and apoptosis in A549 cells following siRNA-induced downregulation of HAb18G

VSL#3 probiotics can be effective on induction and maintenance of the remission of clinical ulcerative colitis. However, the mechanisms are not fully understood. The aim of this study was to examine the effects of VSL#3 probiotics on dextran sulfate sodium (DSS)-induced colitis in rats. Acute colitis was induced by administration of DSS 3.5 % for 7 days in rats. Rats in two groups were treated with either 15 mg VSL#3 or placebo via gastric tube once daily after induction of colitis; rats in other two groups were treated with either the wortmannin (1 mg/kg) via intraperitoneal injection or the wortmannin + VSL#3 after induction of colitis. Anti-inflammatory activity was assessed by myeloperoxidase (MPO) activity. Expression of inflammatory related mediators (iNOS, COX-2, NF-κB, Akt, and p-Akt) and cytokines (TNF-α, IL-6, and IL-10) in colonic tissue were assessed. TNF-α, IL-6, and IL-10 serum levels were also measured. Our results demonstrated that VSL#3 and wortmannin have anti-inflammatory properties by the reduced disease activity index and MPO activity. In addition, administration of VSL#3 and wortmannin for 7 days resulted in a decrease of iNOS, COX-2, NF-κB, TNF-α, IL-6, and p-Akt and an increase of IL-10 expression in colonic tissue. At the same time, administration of VSL#3 and wortmannin resulted in a decrease of TNF-α and IL-6 and an increase of IL-10 serum levels. VSL#3 probiotics therapy exerts the anti-inflammatory activity in rat model of DSS-induced colitis by inhibiting PI3K/Akt and NF-κB pathway.     

Effect of Low-Selenium/High-Fat Diet on Pig Peripheral Blood Lymphocytes: Perspectives from Selenoproteins,Heat Shock Proteins,and Cytokines

The aim of the present study was to clarify the effect of low selenium (Se)/high fat on the mRNA expression of selenoproteins, heat shock proteins (HSPs) and cytokines in pig peripheral blood lymphocytes. Forty crossbred boar piglets with healthy lean body weights of 10 kg were randomly divided into four treatment groups (group C, group L-Se, group H-fat, and group L-Se-H-fat) (n = 10/group) and fed with the corresponding diet for 16 weeks. The pig peripheral blood lymphocytes were extracted, and the mRNA expression of selenoproteins, HSPs, and cytokines was measured. Most mRNA levels for selenoproteins decreased in group L-Se, group H-fat, and group L-Se-H-fat, except Gpx1, Gpx2, Selt, and Selm, which were elevated in group H-fat. At the same time, low-Se/high-fat diet increased the expression of HSPs (HSP40, HSP60, HSP70, and HSP90) and inflammatory cytokines (IL-1α, IL-1β, IL-6, IL-8, IL-9, iNOS, COX-2, NF-κB, and TNF-α) in group L-Se, group H-fat, and group L-Se-H-fat, and genes in group L-Se-H-fat showed greater increases. Also, low-Se/high-fat diet inhibits the expression of TGF-β1 and IFN-γ. In summary, a low-Se/high-fat diet can cause relevant selenoprotein expression changes and promote the expression of pro-inflammatory factors and HSPs, and low Se enhances the expression of HSPs and inflammation factors induced by high fat. This information is helpful for understanding the effects of low-Se and high-fat diet on pig peripheral blood lymphocytes.     

The effect of oxidized low density lipoprotein (oxLDL)-induced heme oxygenase-1 on LPS-induced inflammation in RAW 264.7 macrophage cells

Macrophages take up oxidized low density lipoprotein (oxLDL) after being exposed to it in the blood vessels. oxLDL transforms macrophages into foam cells, which are a hallmark of atherosclerosis. The effects that oxLDL have on the inflammatory responses of foam cells are not clear. Here, we investigated how oxLDL modulates lipopolysaccharide (LPS)-induced inflammatory mediators in RAW 264.7 murine macrophages. Our results showed that oxLDL dramatically induced HO-1 expression, but did not increase pro-inflammatory mediators such as interleukin-1β, tumor necrosis factor-α, iNOS, and monocyte chemoattractant protein (MCP)-1. In RAW 264.7 macrophages, oxLDL markedly inhibited LPS-induced inflammatory mediators such as inducible nitric oxide synthase (iNOS), IL-1β, IL-6, granulocyte macrophage colony-stimulating factor and stromal cell-derived factor-1. Interestingly, however, the down-regulation of HO-1 by siRNA did not recover the inhibition of LPS-induced expression and/or the secretion of inflammatory mediators. oxLDL blocked LPS-induced NF-κB nuclear translocation by inhibiting inhibitory κB (IκB) degradation. Taken together, our results suggest that oxLDL could modulate LPS-induced inflammatory responses by inhibiting NF-κB signaling independently of HO-1 expression.     

下调血管生成素样蛋白7表达对血管紧张素Ⅱ介导的血管平滑肌细胞炎症反应的影响

目的探讨RNA干扰血管生成素样蛋白7 （Angptl7）基因对血管紧张素Ⅱ（AngⅡ）诱导的血管平滑肌细胞（VSMC）炎症因子的影响及其作用机制。 方法体外培养人VSMC,分为常规F12K培养基培养（对照）和1 μg/mL AngII培养24 h。VSMC用AngⅡ（1 μg/mL）处理24 h后,采用siRNA-Angptl7和阴性对照siRNA-NC在Lipofectamine 2000介导下转染VSMC。RT-qPCR检测mRNA表达水平;Griess反应测定一氧化氮（NO）含量;蛋白免疫印记法检测相关蛋白的改变;酶联免疫吸附法检测VSMC中炎症因子肿瘤坏死因子α（TNF-α）、白细胞介素-1β （IL-1β）和IL-6水平。多组间比较采用单因素方差分析,组间两两比较采用LSD-t检验,两组间比较采用独立样本t检验。 结果与对照比较,1 μg/mL AngⅡ处理可促进VSMC中Angptl7 mRNA （0.97±0.06比3.05±0.21）和蛋白表达（1.01±0.12比1.61±0.14）,亦可促进VSMC中IL-1β[（45.21±8.10）比（126.17±11.77） pg/mL]、IL-6[（50.50±7.51）比（108.50±9.51）pg/mL]和TNF-α的表达[（60.77±9.58）比（185.67±17.35）pg/mL],差异有统计学意义（P均< 0.01）。与对照和转染siRNA-NC相比,转染siRNA-Angptl7下调Angptl7蛋白表达（0.99±0.12,0.98±0.12比0.44±0.14,P < 0.01）。与AngⅡ干预组相比,siRNA-Angptl7降低AngⅡ介导的VSMC炎症反应相关蛋白TNF-α、IL-6和IL-1β的表达,核因子κB （NF-κB）/诱导型一氧化氮合酶（iNOS）/环氧化酶2 （COX-2）信号通路相关蛋白NF-κB、iNOS和COX-2表达及NO含量亦降低,差异有统计学意义（P均< 0.01）。与siRNA-NC相比,siRNA-Angptl7组AngⅡ诱导的VSMC炎症反应相关蛋白TNF-α （0.99±0.13比0.51±0.12）、IL-6 （1.00±0.12比0.38±0.05）和IL-1β的表达（0.99±0.14比0.48±0.11）,NF-κB （1.00±0.10比0.42±0.08）、iNOS （1.02±0.12比0.42±0.10）和COX-2表达（1.00±0.11比0.52±0.12）均降低,NO含量[（54.78±2.76）比（18.08±3.61）μmol/L]亦降低,差异有统计学意义（P均< 0.01）。 结论AngⅡ可通过Angptl7促进VSMC炎症反应,下调Angptl7蛋白表达可以抑制VSMC的炎症反应,其作用机制可能与抑制NF-κB/iNOS-COX-2信号通路有关。     

Anti-neuroinflammatory Effect of Emodin in LPS-Stimulated Microglia: Involvement of AMPK/Nrf2 Activation

AMPK/Nrf2 signaling regulates multiple antioxidative factors and exerts neuroprotective effects. Emodin is one of the main bioactive components extracted from Polygonum multiflorum, a plant possessing important activities for human health and for treating a variety of diseases. This study examined whether emodin can activate AMPK/Nrf2 signaling and induce the expression of genes targeted by this pathway. In addition, the anti-neuroinflammatory properties of emodin in lipopolysaccharide (LPS)-stimulated microglia were examined. In microglia, the emodin treatment increased the levels of LKB1, CaMKII, and AMPK phosphorylation. Emodin increased the translocation and transactivity of Nrf2 and enhanced the levels of HO-1 and NQO1. In addition, the emodin-mediated expression of HO-1 and NQO1 was attenuated completely by an AMPK inhibitor (compound C). Moreover, emodin decreased dramatically the LPS-induced production of NO and PGE₂ as well as the protein expression and promoter activity of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). In addition, emodin effectively inhibited the production of pro-inflammatory cytokines, TNF-α and IL-6, and reduced the level of IκBα phosphorylation, leading to the suppression of the nuclear translocation, phosphorylation, and transactivity of NF-κB. Emodin also suppressed the LPS-stimulated activation of STATs, JNK, and p38 MAPK. The anti-inflammatory effects of emodin were reversed by transfection with Nrf-2 and HO-1 siRNA and by a co-treatment with an AMPK inhibitor. These results suggest that emodin isolated from P. multiflorum can be used as a natural anti-neuroinflammatory agent that exerts its effects by inducing HO-1 and NQO1 via AMPK/Nrf2 signaling in microglia.     

Effects of Selenium-Enriched Agaricus blazei Murill on Liver Metabolic Dysfunction in Mice,a Comparison with Selenium-Deficient Agaricus blazei Murill and Sodium Selenite

In the present study, we investigated the effects of Se-enriched Agaricus blazei Murill (Se-AbM) on liver injury in mice induced by acute alcohol administration. Mice received ethanol (5 g/kg body weight (BW)) by gavage every 12 h for a total of 3 doses. Se-AbM was administrated before ethanol administration. Subsequent serum alanine aminotransferase (ALT) level, aspartate aminotransaminase (AST) level, maleic dialdehyde (MDA) level, hepatic total antioxidant status (TAOS), nuclear factor kappa B (NF-κB) level, polymorphonuclear cells (PMN) level, interleukin-1β (IL-1β) level, inducible nitric oxide synthase (iNOS) level, tumor necrosis factor-α (TNF-α) level, intercellular adhesion molecule 1 (ICAM-1), and cyclooxygenase-2 (COX-2) were determined by ELISA and immunohistochemistry, respectively. Se-AbM administration markedly (p?<?005) decreased serum ALT, AST, and MDA levels, hepatic IL-1β and TNF-α levels, as well as PMN infiltration and the expression of ICAM-1, COX-2, iNOS, and NF-κB compared with alcohol administration. In conclusion, we observed that Se-AbM supplementation could restrain the hepatic damage caused by acute alcohol exposure.     

Nitric oxide augments oridonin-induced efferocytosis by human histocytic lymphoma U937 cells via autophagy and the NF-κB-COX-2-IL-1β pathway

Abstract We previously demonstrated that oridonin-induced autophagy enhanced efferocytosis (phagocytosis of apoptotic cells) by macrophage-like U937 cells through activation of the inflammatory pathways. In this study, exposure of U937 cells to 2.5 μM oridonin caused up-regulation of inducible nitric oxide synthase (iNOS) expression and continuous endogenous generation of nitric oxide (NO), which was reversed by pre-treatment with the inhibitors of nitric oxide synthase 1400 W (dihydrochloride) or L-NAME (hydrochloride). NO donor sodium nitroprusside (SNP) and efferocytosis irritant lipopolysaccharide (LPS) could also exert NO generation and iNOS expression. Moreover, oridonin-induced stimulation of efferocytosis was significantly suppressed by 1400 W or L-NAME. In addition, 1400 W or L-NAME impaired oridonin-induced autophagy. Inhibition of autophagy with 3-methyladenine (3MA) or Beclin-1 siRNA attenuated the uptake of apoptotic cells with a slight increase in the production of NO. The pro-inflammatory cytokine interleukin-1β (IL-1β) has been reported to be involved in oridonin-induced efferocytosis in U937 cells and interact with NO to contribute to inflammatory responses. 1400 W or L-NAME blocked the secretion of IL-1β and the activation of NF-κB and COX-2. Provision of SNP or LPS in place of oridonin resulted in the similar enhancement of efferocytosis, autophagy, the release of IL-1β and the expression of signal protein. NO augmented the oridonin-induced efferocytosis by mediating autophagy and activating the NF-κB-COX-2-IL-1β pathway. Inhibition of NF-κB or COX-2 in turn decreased the production of NO and the expression of iNOS. There exists a positive feedback loop between NO generation and NF-κB-COX-2-IL-1β pathway.     

Induction of heme oxygenase-1 protects mouse liver from apoptotic ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is the main cause of primary graft dysfunction of liver allografts. Cobalt-protoporphyrin (CoPP)–dependent induction of heme oxygenase (HO)-1 has been shown to protect the liver from I/R injury. This study analyzes the apoptotic mechanisms of HO-1-mediated cytoprotection in mouse liver exposed to I/R injury. HO-1 induction was achieved by the administration of CoPP (1.5 mg/kg body weight i.p.). Mice were studied in in vivo model of hepatic segmental (70 %) ischemia for 60 min and reperfusion injury. Mice were randomly allocated to four main experimental groups (n = 10 each): (1) A control group undergoing sham operation. (2) Similar to group 1 but with the administration of CoPP 72 h before the operation. (3) Mice undergoing in vivo hepatic I/R. (4) Similar to group 3 but with the administration of CoPP 72 h before ischemia induction. When compared with the I/R mice group, in the I/R+CoPP mice group, the increased hepatic expression of HO-1 was associated with a significant reduction in liver enzyme levels, fewer apoptotic hepatocytes cells were identified by morphological criteria and by immunohistochemistry for caspase-3, there was a decreased mean number of proliferating cells (positively stained for Ki67), and a reduced hepatic expression of: C/EBP homologous protein (an index of endoplasmic reticulum stress), the NF-κB’s regulated genes (CIAP2, MCP-1 and IL-6), and increased hepatic expression of IκBa (the inhibitory protein of NF-κB). HO-1 over-expression plays a pivotal role in reducing the hepatic apoptotic IR injury. HO-1 may serve as a potential target for therapeutic intervention in hepatic I/R injury during liver transplantation.     

Regulation of lipopolysaccharide-induced inflammatory response by heat shock protein 27 in THP-1 cells

HSP27 is a member of the small HSP family which has been linked to different signaling pathways regulating critical cellular functions. But the role of HSP27 in LPS-induced inflammatory signaling pathways is still unclear. In the present study, both overexpression and RNA interference experiments indicated that HSP27 increased LPS-induced expression of iNOS and COX-2 and release of NO/PGE2 through enhancing NF-κB but not MAPK activation. The effects of HSP27 on LPS-induced iNOS/COX-2 expression and relative signaling cascade were closely related with the phosphorylation of HSP27. Further studies have shown that HSP27-regulated LPS-induced activation of NF-κB by interacting with TRAF6 and increasing the association of TRAF6-IKKγ. This could be a probable mechanism by which HSP27 modulates LPS-induce inflammatory signaling pathways. Thus, HSP27 may play a potential role in regulating inflammatory responses in immunologic system.     

Ataxia telangiectasia mutated inhibits oxidative stress-induced apoptosis by regulating heme oxygenase-1 expression

Ataxia telangiectasia (AT) is caused by mutational inactivation of the ataxia telangiectasia mutated (Atm) gene, which is involved in DNA repair. Increased oxidative stress has been shown in human AT cells and neuronal tissues of Atm-deficient mice. Heme oxygenase-1 (HO-1) is an inducible antioxidant enzyme and protects cells against oxidative stress. The purpose of this study is to determine whether ATM induces antioxidant enzyme HO-1 and protects cells from oxidative stress-mediated apoptosis by driving the activation of PKC-δ and NF-κB, by increasing cell viability, and by downregulating DNA fragmentation and apoptotic indicators (apoptosis-inducing factor and cleaved caspase-3). AT fibroblasts stably transfected with human full-length ATM cDNA (YZ5 cells) or the empty vector (MOCK cells) were treated with H₂O₂ as a source of reactive oxygen species (ROS). As a result, transfection with ATM inhibited ROS-induced cell death and DNA fragmentation in MOCK cells. Transfection with ATM induced expression of HO-1 which was mediated by PKC-δ and NF-κB in H₂O₂-treated MOCK cells. ZnPP, an HO-1 inhibitor, and transfection with HO-1 siRNA increased ROS levels and apoptosis, whereas hemin, an HO-1 activator, reduced ROS levels and apoptosis in H₂O₂-treated YZ5 cells. Rottlerin, a PKC-δ inhibitor, inhibited NF-κB activation and HO-1 expression in H₂O₂-treated YZ5 cells. MOCK cells showed increased cell death, DNA fragmentation, and apoptotic indicators compared to YZ5 cells exposed to H₂O₂. In addition, transfection with p65 siRNA increased ROS levels and DNA fragmentation, but decreased HO-1 protein levels in H₂O₂-treated YZ5 cells. In conclusion, ATM induces HO-1 expression via activation of PKC-δ and NF-κB and inhibits oxidative stress-induced apoptosis. A loss of HO-1 induction may explain why AT patients are vulnerable to oxidative stress.