钙和钙调素对机械刺激诱导的烟草悬浮培养细胞耐热性的调控

机械刺激（mechanical stimulation,MS）可提高烟草悬浮培养细胞的钙调素（calmodulin,CaM）活性,诱导烟草悬浮培养细胞耐热性的形成,外源Ca2＋可加强,而Ca2＋螯合剂EGTA、质膜Ca2＋通道阻塞剂La3＋和胞内Ca2＋通道阻断剂钌红（RR）,以及CaM拮抗剂氯丙嗪（CPZ）和三氟拉嗪（TFP）则削弱这种耐热性的形成。这些暗示Ca2＋和CaM参与MS诱导的烟草悬浮培养细胞耐热性形成的调控。     

钙信使系统对机械刺激诱导的烟草悬浮培养细胞中H_2O_2爆发的调控

机械刺激可诱导烟草悬浮培养细胞H2O2的爆发,外源Ca2＋有强化作用,而Ca2＋螯合剂EGTA、质膜Ca2＋通道阻塞剂La3＋、胞内Ca2＋通道阻断剂钌红,以及钙调素拮抗剂氯丙嗪和三氟拉嗪则削弱机械刺激诱导的氧化爆发。这暗示以钙和钙调素为核心的钙信使系统对机械刺激诱发的烟草悬浮培养细胞中H2O2的爆发有调控作用。     

NO对He-Ne激光和增强UV-B辐射小麦幼苗气孔运动的作用机理研究

为探讨NO对He-Ne激光和增强UV-B辐射小麦（Triticum aestivuml）气孔运动的作用机理,采用低剂量（5 mW.mm-2）He-Ne激光和增强（10.08 kJ.m-2.d-1）UV-B辐射并结合药理学实验和激光共聚焦显微技术,对ML7113小麦的叶片及表皮条进行不同的处理,结果显示：（1）UV-B辐射既可诱导小麦叶片气孔关闭,又能够明显增加气孔保卫细胞和叶片的NO水平,且NO清除剂明显抑制了UV-B辐射诱导的小麦叶片气孔关闭,同时气孔保卫细胞和叶片内的NO含量明显减少。（2）一氧化氮合酶（NOS）抑制剂L-NAME对经UV-B辐射诱导的小麦幼苗气孔开度及保卫细胞和叶片内NO含量的抑制程度明显大于硝酸还原酶（NR）抑制剂NaN3对其的抑制程度,说明一氧化氮合酶（NOS）合成途径是小麦叶片经UV-B辐射后NO的主要产生途径。（3）就气孔开度而言,L〉CK〉BL〉B。就小麦叶片及保卫细胞内NO含量而言,B〉BL〉CK〉L。就硝酸还原酶（NR）和一氧化氮合酶（NOS）的活性而言,B组NR活性最低,NOS活性最高,L组NR活性最高,NOS活性最低。表明经He-Ne激光和增强UV-B辐射诱导的小麦气孔开度的变化确实与保卫细胞及叶片中NO含量的多少有关,气孔开度的减小及增大对应于NO含量的增多或减少,同时进一步证实了小麦叶片经He-Ne激光单独辐照后,NO的主要合成途径也来源于NOS途径。     

NO可能作为Ca^2＋的下游信号介导乙烯诱导的蚕豆气孔关闭

以蚕豆（Vicia faba L．）为材料,利用药理学实验,结合激光共聚焦显微技术和分光光度法．探讨Ca^2＋和一氧化氮（nitric oxide,NO）在乙烯（ethylene,Eth）调控气孔运动信号转导中的作用。结果表明．光下乙烯利（0．004％,0．04％,0．4％）可诱导蚕豆叶片气孔关闭,且具有时间和剂量效应：NO清除剂cPTIO、硝酸还原酶（nitrate reductase,NR）抑制剂NaN3及胞外Ca^2＋螯合剂EGTA可部分逆转乙烯诱导的气孔关闭;乙烯能够明显增加气孔保卫细胞NO水平;提高蚕豆叶片NO含量和NR活性．并且NO的含量变化与NR活性的变化趋势基本一致;NR抑制剂NaN3可抑制乙烯诱导的气孔保卫细胞和叶片NO含量的增加;清除胞外Ca^2＋可减弱乙烯对NO含量和NR活性的诱导效应。说明Ca^2＋和NO均参与乙烯诱导的蚕豆气孔关闭,且NO（主要由NR途径合成）可能位于Ca^2＋下游参与调控这一信号转导过程。     

哺乳动物Bax基因依赖NO信号途径诱发长春花细胞中生物碱合成

哺乳动物细胞凋亡基因Bax是最近发现的一种对植物细胞次生代谢产物合成具有复合调控作用的新型调控因子. 为了研究Bax诱发植物次生代谢产物合成的分子机理, 本文测定了小鼠Bax对长春花(Catharanthus roseus)细胞中一氧化氮(NO)合成积累的影响, 并考察了NO专一性抑制剂cPITO对小鼠Bax诱发长春花碱及总生物碱合成的影响. 实验结果表明, 小鼠Bax可以诱导长春花细胞NO迸发. cPITO不仅能够抑制Bax对NO迸发的诱导作用, 还可以阻断Bax对长春花碱及总生物碱合成的促进作用. 实验结果说明, 小鼠Bax可以激活长春花细胞中NO信号转导事件并依赖NO信号途径介导长春花碱等次生代谢产物合成. 进一步实验表明, 小鼠Bax可以诱导长春花细胞中一氧化氮合酶(NOS)活性, NOS抑制剂PBITU可以阻碍小鼠Bax对NO和长春花碱合成的促进作用, 说明小鼠Bax可以依赖NOS诱发长春花细胞中NO产生和长春花碱生物合成.比较细胞中NO迸发和NOS活化的动力学过程发现, Bax对NOS活性的诱导作用明显迟于NO产生, 而且NOS活性远低于细胞中NO的产生量. 此外, PBITU只能部分抑制小鼠Bax对长春花生物碱合成的促进作用. 上述实验结果表明, NOS可能不是小鼠Bax诱发长春花细胞NO迸发和长春花碱生物合成的唯一途径.     

壳寡糖诱导植物防御反应中一氧化氮信号的研究

壳寡糖可以增强植物对病虫害的防御能力,为了深入研究壳寡糖的作用机理,首次运用荧光酶标仪及一氧化氮(Nitric oxide,NO)荧光探针Diaminofluorescein diacetate (DAF-2DA)对壳寡糖诱导的NO信号进行研究。研究发现,不同浓度的壳寡糖均可诱导烟草悬浮细胞产生NO;NO的清除剂Carboxy-PTIO potassium salt(cPTIO)和一氧化氮合酶(Nitric oxide synthase,NOS)抑制剂N^ω-nitro-L-arginine methyl Ester(L-NAME)可以明显抑制NO的产生;硝酸还原酶(Nitrate reductase, NR)的抑制剂叠氮化钠和钨酸钠对NO的产生无影响;Ca²⁺流相关抑制剂氯化镧和钌红均可抑制NO的产生。NO和Ca²⁺流的相关抑制剂可明显抑制壳寡糖诱导的抗性相关基因的表达。结果显示:壳寡糖主要通过NOS酶催化合成NO,且NO参与调节壳寡糖诱导的抗性相关基因的表达,在此过程中,Ca²⁺可以调节NO的合成。     

哺乳动物Bax基因依赖NO信号途径诱发长春花细胞中生物碱合成

哺乳动物细胞凋亡基因Bax是最近发现的一种对植物细胞次生代谢产物合成具有复合调控作用的新型调控因子. 为了研究Bax诱发植物次生代谢产物合成的分子机理, 本文测定了小鼠Bax对长春花(Catharanthus roseus)细胞中一氧化氮(NO)合成积累的影响, 并考察了NO专一性抑制剂cPITO对小鼠Bax诱发长春花碱及总生物碱合成的影响. 实验结果表明, 小鼠Bax可以诱导长春花细胞NO迸发. cPITO不仅能够抑制Bax对NO迸发的诱导作用, 还可以阻断Bax对长春花碱及总生物碱合成的促进作用. 实验结果说明, 小鼠Bax可以激活长春花细胞中NO信号转导事件并依赖NO信号途径介导长春花碱等次生代谢产物合成. 进一步实验表明, 小鼠Bax可以诱导长春花细胞中一氧化氮合酶(NOS)活性, NOS抑制剂PBITU可以阻碍小鼠Bax对NO和长春花碱合成的促进作用, 说明小鼠Bax可以依赖NOS诱发长春花细胞中NO产生和长春花碱生物合成.比较细胞中NO迸发和NOS活化的动力学过程发现, Bax对NOS活性的诱导作用明显迟于NO产生, 而且NOS活性远低于细胞中NO的产生量. 此外, PBITU只能部分抑制小鼠Bax对长春花生物碱合成的促进作用. 上述实验结果表明, NOS可能不是小鼠Bax诱发长春花细胞NO迸发和长春花碱生物合成的唯一途径.     

NO参与γ-氨基丁酸促进白三叶种子的萌发过程

白三叶种子用不同浓度γ-氨基丁酸（GABA）处理后,低浓度GABA处理的白三叶种子萌发速率和一氧化氮（NO）含量显著提高;NO清除剂cPTIO和硝酸还原酶（NR）抑制剂叠氮钢（NaN3）显著抑制GABA促进的白三叶种子萌发过程,而一氧化氮合酶（NOS）抑制剂L-NAME对GABA促进白三叶种子萌发的影响不显著。据此推测,GABA促进白三叶种子萌发过程中可能有NO参与,并且NO的产生主要依赖于硝酸还原酶途径。     

Ca~(2+)参与NO对蚕豆气孔运动的调控

观察了Ca2 + 、Ca2 + 的螯合剂和Ca2 + 通道抑制剂对NO调控的蚕豆气孔运动的影响。结果表明 ,NO的供体 1～ 10 0 μmol/LSNP (sodiumnitroprusside ,硝普纳 )可诱导气孔关闭 ;除去表皮条缓冲液中的Ca2 + 后 ,NO不再影响气孔的运动 ;Ca2 + 的螯合剂EGTA和BAPTA几乎可以完全抑制NO诱导的气孔关闭作用 ;胞内钙通道抑制剂钌红 (rutheniumred)和L型Ca2 + 通道阻断剂硝苯吡啶 (nifedipine)能够减弱SNP诱导气孔运动的关闭趋势 ;加入Ca2 + 通道抑制剂LaCl3 ,则外源NO失去其诱导气孔关闭的作用。说明在NO调控的气孔运动中 ,在NO信号途径的下游可能涉及来自胞内和胞外Ca2 + 的参与 ,并且胞外Ca2 + 更为重要。     

Cd~（2＋）胁迫诱导烟草悬浮细胞脯氨酸积累的生化途径及外源脯氨酸对Cd~（2＋）胁迫下H_2O_2产生的抑制作用

Cd~（2＋）可提高烟草悬浮细胞脯氨酸的含量,顺序上调脯氨酸合成关键酶鸟氨酸转氨酶（OAT）、精氨酸酶、△~1-吡咯啉-5-羧酸合成酶（P5CS）和谷氨酸脱氢酶（GDH）的活性,降低脯氨酸降解关键酶脯氨酸脱氢酶（ProDH）的活性,表明Cd~（2＋）胁迫诱导烟草细胞脯氨酸的积累是脯氨酸合成的鸟氨酸途径和谷氨酸途径顺序激活、而脯氨酸降解途径显著抑制的综合结果。此外,Cd~（2＋）能导致烟草细胞H_2O_2的快速产生及H_2O_2产生相关酶（质膜NADPH氧化酶、细胞壁多胺氧化酶及共价结合与离子结合细胞壁过氧化物酶）活性升高和脂质过氧化产物丙二醛（MDA）增加,导致烟草细胞的氧化胁迫。外源脯氨酸预处理显著抑制了Cd~（2＋）诱导的烟草细胞H_2O_2的产生与MDA的增加,减轻了Cd~（2＋）诱导的氧化胁迫。而脯氨酸抑制Cd~（2＋）诱导的H_2O_2产生可能是由于脯氨酸抑制了H_2O_2产生相关酶的活性所致。     

Extremely low frequency magnetic field induces hyperalgesia in mice modulated by nitric oxide synthesis

We investigated an effect of extremely low frequency magnetic field (ELF-MF, 60 Hz) on hyperalgesia using hot plate test. The level of nitric oxide (NO) and the expression of nitric oxide synthase (NOS) were measured to determine if ELF-MF is engaged in NO mediated pain mechanism. Additionally, the involvement of Ca2+-dependent NO pathway in ELF-MF induced hyperalgesia was evaluated by blocking Ca2+ sources with NMDA receptor antagonist and Ca2+ channel blocker. The exposure of mice to ELF-MF lowered pain threshold and elevated NO synthesis in brain and spinal cord. An NOS inhibitor blocked these effects of ELF-MF with attenuating the reduction of pain threshold and the rise of NO level in brain and spine by the exposure of ELF-MF. The hyperalgesic effects of ELF-MF were also blocked by a Ca2+ channel blocker, nimodipine, but not by a NMDA receptor antagonist, MK-801. The expression of Ca2+ -dependent nNOS and eNOS and Ca2+ -independent iNOS were not changed by ELF-MF. These results indicated that the exposure of ELF-MF might cause Ca2+ -dependent NOS activation, which then induces hyperalgesia with the increase in NO synthesis. In conclusion, ELF-MF may produce hyperalgesia by modulating NO synthesis via Ca2+ -dependent NOS.     

Enhancement of nitric oxide production by association of nitric oxide synthase with N-methyl-D-aspartate receptors via postsynaptic density 95 in genetically engineered Chinese hamster ovary cells: real-time fluorescence imaging using nitric oxide sensitive dye

The current quantitative study demonstrates that the recruitment of neuronal nitric oxide synthase (nNOS) beneath N-methyl-D-aspartate (NMDA) receptors, via postsynaptic density 95 (PSD-95) proteins significantly enhances nitric oxide (NO) production. Real-time single-cell fluorescence imaging was applied to measure both NO production and Ca(2+) influx in Chinese hamster ovary (CHO) cells expressing recombinant NMDA receptors (NMDA-R), nNOS, and PSD-95. We examined the relationship between the rate of NO production and Ca(2+) influx via NMDA receptors using the NO-reactive fluorescent dye, diaminofluorescein-FM (DAF-FM) and the Ca(2+)-sensitive yellow cameleon 3.1 (YC3.1), conjugated with PSD-95 (PSD-95-YC3.1). The presence of PSD-95 enhanced the rate of NO production by 2.3-fold upon stimulation with 100 microm NMDA in CHO1(+) cells (expressing NMDA-R, nNOS and PSD-95) when compared with CHO1(-) cells (expressing NMDA-R and nNOS lacking PSD-95). The presence of nNOS inhibitor or NMDA-R blocker almost completely suppressed this NMDA-stimulated NO production. The Ca(2+) concentration beneath the NMDA-R, [Ca(2+)](NR), was determined to be 5.4 microm by stimulating CHO2 cells (expressing NMDA-R and PSD-95-YC3.1) with 100 microm NMDA. By completely permealizing CHO1 cells with ionomycin, a general relationship curve of the rate of NO production versus the Ca(2+) concentration around nNOS, [Ca(2+)](NOS), was obtained over the wide range of [Ca(2+)](NOS). This sigmoidal curve had an EC(50) of approximately 1.2 microm of [Ca(2+)](NOS), implying that [Ca(2+)](NR) = 5.4 microm can activate nNOS effectively.     

Changes in the level of cytosolic calcium, nitric oxide and nitric oxide synthase activity during platelet aggregation: an in vitro study in platelets from normal subjects and those with cirrhosis

Variceal bleeding due to abnormal platelet function is a well-known complication of cirrhosis. Nitric oxide-related stress has been implicated in the pathogenesis of liver cirrhosis.In the present investigation,we evaluated the level of platelet aggregation and concomitant changes in the level of platelet cytosolic calcium (Ca2+), nitric oxide (NO) and NO synthase (NOS) activity in liver cirrhosis.The aim of the present study was to investigate whether the production of NO by NOS and level of cytosolic Ca2+ influence the aggregation of platelets in patients with cirrhosis of the liver.Agonist-induced aggregation and the simultaneous changes in the level of cytosolic Ca2+, NO and NOS were monitored in platelets of patients with cirrhosis.Platelet aggregation was also measured in the presence of the eNOS inhibitor,diphenylene iodinium chloride (DIC).The level of agonist-induced platelet aggregation was significantly low in the platelets of patients with cirrhosis compared with that in platelets from normal subjects.During the course of platelet aggregation,concomitant elevation in the level of cytosolic Ca2+ was observed in normal samples,whereas the elevation was not significant in platelets of patients with cirrhosis.A parallel increase was observed in the levels of NO and NOS activity.In the presence of the eNOS inhibitor,platelet aggregation was enhanced and accompanied by an elevated calcium level.The inhibition of platelet aggregation in liver cirrhosis might be partly due to greater NO formation by eNOS.Defective Ca2+ release from the internal stores to the cytosol may account for inhibition of aggregation of platelets in cirrhosis.The NO-related defective aggregation of platelets in patients with cirrhosis found in our study is of clinical importance,and the underlying mechanism of such changes suggests a possible therapeutic strategy with cell-specific NO blockers.     

Cross-talk between calcium-calmodulin and nitric oxide in abscisic acid signaling in leaves of maize plants

Using pharmacological and biochemical approaches, the signaling pathways between hydrogen peroxide （H2O2）, calcium （Ca^2＋）-calmodulin （CAM）, and nitric oxide （NO） in abscisic acid （ABA）-induced antioxidant defense were investigated in leaves of maize （Zea mays L.） plants. Treatments with ABA, H2O2, and CaCl2 induced increases in the generation of NO in maize mesophyll cells and the activity of nitric oxide synthase （NOS） in the cytosolic and microsomal fractions of maize leaves. However, such increases were blocked by the pretreatments with Ca^2＋ inhibitors and CaM antagonists. Meanwhile, pretreatments with two NOS inhibitors also suppressed the Ca^2＋-induced increase in the production of NO. On the other hand, treatments with ABA and the NO donor sodium nitroprusside （SNP） also led to increases in the concentration of cytosolic Ca^2＋ in protoplasts of mesophyll cells and in the expression of calmodulin 1 （CaM1） gene and the contents of CaM in leaves of maize plants, and the increases induced by ABA were reduced by the pretreatments with a NO scavenger and a NOS inhibitor. Moreover, SNP-induced increases in the expression of the antioxidant genes superoxide dismutase 4 （SOD4）, cytosolic ascorbate peroxidase （cAPX）, and glutathione reductase 1 （GR1） and the activities of the chloroplastic and cytosolic antioxidant enzymes were arrested by the pretreatments with Ca^2＋ inhibitors and CaM antagonists. Our results suggest that Ca^2＋-CaM functions both upstream and downstream of NO production, which is mainly from NOS, in ABA- and H2O2-induced antioxidant defense in leaves of maize plants.     

Sphingomyelinase causes endothelium-dependent vasorelaxation through endothelial nitric oxide production without cytosolic Ca(2+) elevation

Neutral sphingomyelinase (N-SMase) elevated nitric oxide (NO) production without affecting intracellular Ca(2+) concentration ([Ca(2+)](i)) in endothelial cells in situ on aortic valves, and induced prominent endothelium-dependent relaxation of coronary arteries, which was blocked by N(omega)-monomethyl-L-arginine, a NO synthase (NOS) inhibitor. N-SMase induced translocation of endothelial NOS (eNOS) from plasma membrane caveolae to intracellular region, eNOS phosphorylation on serine 1179, and an increase of ceramide level in endothelial cells. Membrane-permeable ceramide (C(8)-ceramide) mimicked the responses to N-SMase. We propose the involvement of N-SMase and ceramide in Ca(2+)-independent eNOS activation and NO production in endothelial cells in situ, linking to endothelium-dependent vasorelaxation.     

Effect of calcitonin gene-related peptide on nitric oxide production in osteoblasts: an experimental study

The aim of this study was to investigate the in vitro effects and regulatory mechanism of CGRP (calcitonin gene-related peptide) on NO (nitric oxide) production in osteoblasts. MOB (primary human mandibular osteoblasts) and osteoblast-like cells (MG-63) were either cultured with CGRP or co-incubated with inhibitors targeting eNOS (endothelial nitric oxide synthase), iNOS (inducible nitric oxide synthase), nNOS (neuronal nitric oxide synthase) and [Ca2+]i (intracellular Ca2+). The NO concentration in cell culture supernatants was measured during the first 24 h using the Griess test; cellular NO was marked with the fluorescent marker DAF-FM, DA (3-amino, 4-aminomethyl-2',7'-difluorescein; diacetate) and measured by fluorescence microscopy from 1 to 4 h after treatment. eNOS and iNOS mRNA expression levels were measured by quantitative RT-PCR during the first 24 h after treatment. CGRP-induced NO production in the supernatants was high between 1 to 12 h, while cellular NO was highest between 1 to 2 h after treatment and returned to basal levels by 3 h. Both in MG-63 cells and MOBs, the most effective CGRP concentration was 10 nM with a peak time of 1 h. CGRP-induced NO production decreased when eNOS activity was inhibited or when voltage-dependent L-type Ca2+ channels were blocked at 4 h. CGRP was not able to induce changes in iNOS or eNOS mRNA levels and had no effect on the cytokine-induced increase of iNOS expression. Our results suggest that CGRP transiently induces NO production in osteoblasts by elevating intracellular Ca2+ to stimulate the activity of eNOS in vitro.     

胰岛素促进血管内皮细胞产生一氧化氮的实验研究

目的：探讨胰岛素对血管内皮细胞增殖、NO产生和NOS基因表达的影响。方法：培养牛主动脉内皮细胞,测定培养上清液中NO氧化产物NO2^－的水平并应用定量RT－PCR技术检测内皮细胞NOS mRNA的表达水平。结果：①胰岛素对大血管内皮细胞无细胞毒作用,也不影响细胞增殖;②在1－15μg/ml浓度范围内,胰岛素加强内皮细胞释放NO,且呈剂量依赖的方式,NOS特异性抑制剂L－NAME可阻抑之;③胰岛素轻度增加NOS mRNA表达水平,但无统计学意义。结论：胰岛素既不影响大血管内皮细胞增殖,也不影响内皮细胞NOS mRNA表达水平,但以剂量依赖的方式加强内皮细胞产生NO,推测其诱导NO产生的机制可能是通过酶活性的诱导,加速NO的合成。     

尾加压素对新生大鼠心肌细胞一氧化氮合成的影响

应用半定量逆转录－多聚酶链反应法,观察尾加压素（urotensin Ⅱ,UⅡ）对培养的新生SD大鼠心肌细胞内皮型一氧化氮合酶（endothelial nitric oxide synthase,eNOS)mRNA表达的影响,并测定UⅡ对心肌细胞内一氧化氮合酶（nitric oxide synthase,NOS)活性和一氧化氮（nitric oxide,NO)释放的影响。结果显示：UⅡ抑制培养的新生大鼠心肌细胞eNOS mRNA表达、抑制NOS的活性及NO释放;0.1μmol/L浓度的UⅡ呈时间依赖性抑制心肌细胞NOS的活性及NO生成。上述实验结果提示UⅡ的心血管作用可能与NO合成系统有关。     

Reactive oxygen species, nitric oxide, and their interactions play different roles in Cupressus lusitanica cell death and phytoalexin biosynthesis

Beta-thujaplicin Is a natural troponoid with strong antifungal, antiviral, and anticancer activities. Beta-thujaplicin production in yeast elicitor-treated Cupressus lusitanica cell culture and its relationships with reactive oxygen species (ROS) and nitric oxide (NO) production and hypersensitive cell death were investigated. Superoxide anion radical (O2*-) induced cell death and inhibited beta-thujaplicin accumulation, whereas hydrogen peroxide (H2O2) induced beta-thujaplicin accumulation but did not significantly affect cell death. Both elicitor and O2*- induced programmed cell death, which can be blocked by protease inhibitors, protein kinase inhibitors, and Ca2+ chelators. Elicitor-induced NO generation was nitric oxide synthase (NOS)-dependent. Inhibition of NO generation by NOS inhibitors and NO scavenger partly blocked the elicitor-induced beta-thujaplicin accumulation and cell death, and NO donors strongly induced cell death. Interaction among NO, H2O2, and O2*- shows that NO production and H2O2 production are interdependent, but NO and O2*- accumulation were negatively related because of coconsumption of NO and O2*-. NO- and O2*- -induced cell death required each other, and both were required for elicitor-induced cell death. A direct interaction between NO and O2*- was implicated in the production of a potent oxidant peroxynitrite, which might mediate the elicitor-induced cell death.     

Knockdown of the inducible nitric oxide synthase (NOS2) splicing variant S3 promotes autophagic cell death from nitrosative stress in SW480 human colon cancer cells

Low levels of nitric oxide (NO) produced by constitutively expressed inducible NO synthase (NOS2) in tumor cells may be an important factor in their development. NOS2 expression is associated with high mortality rates for various cancers. Alternative splicing of NOS2 down-regulates its enzymatic activity, resulting in decreased intracellular NO concentrations. Specific probes to detect alternative splicing of NOS2 were used in two isogenic human colon cancer cell lines derived either from the primary tumor (SW480) or from a lymph node metastasis (SW620). Splicing variant of NOS2 S3, lacking exons 9, 10, and 11, was overexpressed in SW480 cells. NOS2 S3 was silenced in SW480 cells. Flow-cytometry analysis was used to estimate the intracellular NO levels and to analyze the cell cycle of the studied cell lines. Western blot analysis and quantitative real-time polymerase chain reaction (qRT-PCR) were used to determine apoptosis and autophagy markers. SW480 and SW620 cells expressed NOS2 S3. Overexpression of the NOS2 S3 in SW480 cells downregulated intracellular NO levels. SW480 cells with knocked down NOS2 S3 (referred to as S3C9 cells) had higher intracellular levels of NO compared to the wild-type SW480 cells under serum restriction. Higher NO levels resulted in the loss of viability of S3C9 cells, which was associated with autophagy. Induction of autophagy by elevated intracellular NO levels in S3C9 cells under serum restriction, suggests that autophagy operates as a cytotoxic response to nitrosative stress. The expression of NOS2 S3 plays an important role in regulating intracellular NO production and maintaining viability in SW480 cells under serum restriction. These findings may prove significant in the design of NOS2/NO-based therapies for colon cancer.