百草枯对活性氧类物质的产生和中性粒细胞凋亡的影响

目的:探讨百草枯(PQ)对活性氧类物质(ROS)和中性粒细胞凋亡的影响及可能机制。方法:离体培养健康成人中性粒细胞,给予不同浓度百草枯刺激后培养6~24 h,流式细胞仪检测中性粒细胞凋亡率及ROS含量,Western blot检测信号蛋白核因子kappa B(NF-кB)、天冬氨酸特异性半胱氨酸蛋白酶3(Caspase 3);给予ROS、NF-κB拮抗剂后,再次检测中性粒细胞凋亡率及信号蛋白含量。结果:PQ可明显促进ROS产生及抑制中性粒细胞凋亡,这种效应可被ROS抑制剂二联苯碘(DPI)及NF-кB抑制剂四氢吡咯二硫代氨基甲酯(PDTC)逆转。同时,PQ能促进NF-κB表达增加,而Caspase 3表达则受到明显抑制。结论:百草枯是强力的ROS诱导剂,并能抑制中性粒细胞凋亡,其机制可能与NF-κB活化,进而抑制Caspase 3表达有关。     

脓毒症小鼠心肌损伤与中性粒细胞浸润的关系

目的:探讨脓毒症小鼠心肌损伤与中性粒细胞浸润的关系。方法:复制脓毒症动物模型,分对照组、假手术组、造模组,并设不同的时间点(2h、4h、8h、12h)。采用双抗夹心酶联免疫法(ELISA)检测血清肌钙蛋白(IcTnI),并测心肌组织髓过氧化物酶(MPO)活性。结果:正常组与假手术组各时间点血清cTnI、心肌组织MPO活性均无显著性差异。造模组心肌组织MPO活性较正常组和假手术组均有明显升高(P<0.05),且随着时间进展而增加;造模组血清cTnI浓度随着时间进展而增加,2小时与正常组及假手术组无显著性差异(P>0.05),4小时后显著高于正常组和假手术组(P<0.05);血清cTnI浓度与心肌组织MPO活性呈显著正相关(r=0.700,P=0.000)。结论:脓毒症心肌损伤时,心肌组织存在中性粒细胞浸润,中性粒细胞浸润程度与心肌损伤显著正相关。     

莲心碱对LPS诱导小鼠急性肺损伤的保护作用

目的探讨莲心碱对脂多糖(lipopolysaccharide,LPS)诱导的小鼠急性肺损伤(ALI)的作用。方法BALB/c小鼠随机分为对照组、LPS组、LPS+莲心碱(2、4、8 mg/kg)组、地塞米松(5 mg/kg)组,鼻腔滴入法建立LPS诱导的急性肺损伤模型。12 h后,组织学观察肺组织的病理学变化;ELISA检测肺泡灌洗液(BALF)中TNF-α、IL-6和IL-1β的含量;Wright-Giemsa染色检测BALF中中性粒细胞数;BCA法检测总蛋白含量;Evans blue检测肺毛细血管通透性;分光光度法检测肺匀浆上清中MPO的活性、MDA的含量、SOD的活性、GSH的含量;流式细胞术检测肺组织中ROS的含量。结果 LPS组可见肺组织具有炎性细胞浸润、支气管肺泡壁增厚和肺充血现象,而莲心碱组可以改善肺损伤情况;LPS组BALF中TNF-α、IL-6、IL-1β的含量明显增加、中性粒细胞数和总蛋白量显著增多,肺毛细血管通透性、MPO活性和MDA含量增加,SOD活性和GSH含量降低,ROS含量增加,而莲心碱组能够降低BALF中TNF-α、IL-6、IL-1β的含量,减少中性粒细胞数和总蛋白量,降低肺毛细血管通透性,降低MPO活性和MDA含量,增加SOD活性和GSH含量,降低ROS的含量。结论莲心碱可通过抗炎抗氧化作用保护LPS诱导的小鼠急性肺损伤。     

肥厚预刺激对苯肾上腺素诱导的心肌细胞肥大的保护作用

目的:研究不同肥厚预刺激对苯肾上腺素(Phenylephrine,PE)诱导的心肌细胞肥大的影响。方法:胶原酶联合差速贴壁法分离培养原代SD乳鼠心肌细胞后分组:(1)对照组(常规培养48 h);(2)PE组(50μM PE刺激48 h);(3)不同预刺激+PE组:A,不同浓度的PE(10、20、50μM)预刺激(12 h干预,12 h常规培养);B,PE(50μM)预刺激不同时间(period-1,6 h干预,6 h常规培养;period-2,6 h干预,6 h常规培养,再次6 h干预,6 h常规培养;period-3,8 h干预,8 h常规培养;period-4,12 h干预,12 h常规培养)。预刺激后再用PE(50μM)刺激48 h。经细胞骨架蛋白(α-actining)免疫荧光染色,利用激光共聚焦显微镜观察细胞表型,Image J软件计算心肌细胞表面积,利用实时定量PCR检测肥厚相关标志物表达水平。结果:分离的心肌细胞纯度在90%以上。PE组较对照组心肌细胞明显肥大,细胞表面积增加2.3倍,心肌肥厚标记基因心钠肽(atrial natriuretic peptide,ANP)、脑钠肽(brain natriuretic peptide,BNP)和β肌球蛋白重链(βmyosin heavy chain,βMHC)表达明显升高(P0.05);而不同预刺激+PE组心肌细胞肥大表型明显缓解,其中PE(50μM)两次6 h预刺激最为显著(P0.05)。结论:肥厚预刺激可以减轻PE诱导的心肌细胞肥大的程度,从而对心肌肥厚有保护作用。     

肿瘤化疗前应用重组人粒细胞集落刺激因子预防白细胞减少临床研究

目的:了解肿瘤化疗中重组人粒细胞集落刺激因子治疗粒细胞减少症的疗效。方法:本研究受试者为2010年8月至2012年7月在我们医院做化疗的癌症患者,可靠的数据。把接受化疗的测试者随机分为对照组患者和干预组患者,对照组30例,干预组60例(其中30例出现粒细胞减少疾病组,另外30例为以前有粒细胞减少症病史,本次化疗后24 h内入组)。对照组予利血生、鲨肝醇、Vit B4、碳酸锂等一般性治疗;干预组予一般性治疗+rh GCSF治疗。评估粒细胞缺乏时各组间中性粒细胞恢复情况。结果干预组轻、中、重度中性粒细胞数量减少者的中性粒细胞数量较对照组恢复的更快、更好。结论:肿瘤化疗中重组人粒细胞集落刺激因子可有效纠正粒细胞缺乏症,化疗后24 h内即用效果更好。     

即早基因c-fos在THP-1单核巨噬细胞亚型极化中的差异表达*

目的:探讨即早基因c-fos在THP-1巨噬细胞亚型极化过程中的表达变化。方法:运用PMA刺激诱导THP-1单核细胞极化为巨噬细胞,观察c-fos在单核细胞极化过程中的表达变化;在PMA刺激的基础上,分别运用LPS和IL-4诱导THP-1巨噬细胞向M1及M2亚型极化,实时定量PCR及Western blot技术分析刺激24 h时,细胞亚型标记物CD274、CD86和CD163的表达变化,并动态观察诱导极化过程中,c-fos的表达情况。结果:c-fos在PMA刺激THP-1单核细胞分化为巨噬细胞过程中蛋白和mRNA水平显示上调;LPS诱导THP-1巨噬细胞极化为M1型过程中,c-fos蛋白和mRNA水平表达降低,其特异性标记物在24 h呈现出M1型极化的特点(CD86蛋白表达升高,CD274、CD163蛋白表达降低);IL-4诱导THP-1巨噬细胞极化为M2型过程中,c-fos蛋白和mRNA水平表达升高,其特异性标记物在24 h表现出M2型极化的特点(CD86蛋白表达降低,CD274、CD163蛋白表达升高)。结论:c-fos参与了THP-1单核细胞向巨噬细胞极化的过程,并且可能通过抑制巨噬细胞M1亚型形成,促进巨噬细胞向M2亚型极化的作用参与巨噬细胞的亚型极化及其功能调节中。     

M2型巨噬细胞在新月体性肾小球肾炎患者中的临床意义

本研究旨在探讨新月体性肾小球肾炎患者M2型巨噬细胞的临床病理意义,以及M2巨噬细胞标志物CD163和CD206的阳性表达情况。选择不同病因的超过30%以上新月体形成的肾小球性肾炎患者肾组织切片作为研究材料,其中,抗中性粒细胞胞浆抗体相关性血管炎(anti-neutrophil cytoplasmic antibody-associated vasculitis, AAV, n=16)、狼疮性肾炎(lupus nephritis, LN, n=13)、Ig A肾病(Ig A nephropathy, Ig AN, n=10)、紫癜性肾炎(Henoch-Schonlein purpura nephritis, HSPGN, n=10)被纳入本研究。另外,选择微小病变性肾病(minimal change disease, n=6)和正常对照肾脏(n=3)作为阴性对照。免疫组织化学和免疫荧光检测肾组织中CD163和CD206的表达。结果显示,LN和AAV中CD163阳性细胞数量显著高于Ig AN和HSPGN。与Ig AN和HSPGN相比,LN和AAV患者的肾小球病变中存在更多的CD206阳性细胞。CD163和CD206阳性细胞与新月体百分比、肾小球滤过率、血清白蛋白和尿蛋白之间存在显著相关性。总之,M2巨噬细胞参与了新月体性肾小球肾炎的发病机制和疾病进展,特别是在狼疮性肾炎和抗中性粒细胞胞浆抗体相关性血管炎中。     

中性粒细胞胞外诱捕网抗疣状毛癣菌感染的作用研究

目的观察到1例疣状毛癣菌(Trichophyton verrucosum,T.verrucosum)致须癣患者的局部皮损中存在大量中性粒细胞。以往文献报道中性粒细胞通过形成胞外诱捕网(Neutrophils extracellular traps, NETs)参与抗真菌免疫,但T.verrucosum能否诱导NETs形成,及NETs是否具有抗T.verrucosum作用尚不清楚,故探究中性粒细胞是否通过形成NETs参与杀灭T.verrucosum。方法收集患者病历资料。从患者组织分离、鉴定T.verrucosum。免疫荧光法检测患者及T.verrucosum感染小鼠组织中的NETs。T.verrucosum刺激正常人外周血中性粒细胞,免疫荧光法检测NETs的形成。NETs与T.verrucosum共孵育,提取T.verrucosum DNA,通过实时荧光定量PCR定量检测真菌数量,观察NETs对T.verrucosum的杀伤作用。结果 T.verrucosum感染患者及小鼠组织可见明显NETs。T.verrucosum与中性粒细胞共孵育后有明显NETs形成。与NETs孵育后T.verrucosum存活率低于对照组(P0.01)。结论 T.verrucosum可以诱导中性粒细胞产生NETs,NETs对T.verrucosum具有显著杀伤作用。     

活性氧诱发人类11号染色体基因突变

对体外产生的和内源性刺激产生的活性氧 (ROS)诱发人类 11号染色体 (Hchr 11)基因突变规律及其突变谱进行研究 .体外羟自由基 (·OH)用过氧化氢 (H2 O2 )与Fe2 + 反应产生 ,并用化学发光(CL)进行相对定量分析 ;内源性ROS用佛波醇酯 (PMA)刺激人外周血白细胞产生 ,并用CL和特异性抗氧化物检测和鉴定 ;用包含单条Hchr 11的人 中国仓鼠卵巢细胞 (AL)为靶 ,经CD59表面抗原抗体筛选突变细胞克隆 ,研究ROS诱发的Hchr 11基因突变 ;突变克隆细胞DNA用Hchr 11上 5种标志基因引物进行多重PCR分析 ,结合琼脂糖凝胶电泳绘制基因突变谱 .结果表明 ,体外ROS可诱发Hchr 11基因突变 ,且·OH诱发基因突变的能力明显强于H2 O2 ,两者的突变谱也存在明显差异 ;PMA可刺激人外周血白细胞产生大量的多种ROS ,并诱发Hchr 11基因突变 ,突变谱综合了H2 O2 和·OH的所有特征 ;一些抗氧化物对内源性产生的ROS诱发Hchr 11基因突变有明显抑制作用 .提示体外和内源性ROS可诱发Hchr 11基因突变 ,不同的活性氧分子诱发的基因突变可能具有特异性     

Reactive oxygen species‐induced activation of ERK and p38 MAPK mediates PMA‐induced NETs release from human neutrophils

Neutrophils/polymorphonuclear leukocytes (PMNs), an important component of innate immune system, release extracellular traps (NETs) to eliminate invaded pathogens; however understanding of the role of signaling molecules/proteins need to be elucidated. In the present study role of p38 MAPK and extracellular signal regulated kinase (ERK) against phorbol 12‐myristate 13‐acetate (PMA) induced reactive oxygen species (ROS) generation and NETs formation has been investigated. Human neutrophils were treated with PMA to induce free radical generation and NETs release, which were monitored by NBT reduction and elastase/DNA release, respectively. PMA treatment led to the time dependent phosphorylation of p38 MAPK and ERK in PMNs. Pretreatment of PMNs with SB202190 or U0126 did not significantly reduce PMA induce free radical generation, but prevented NETs release. Pretreatment of PMNs with NADPH oxidase inhibitor (diphenyleneiodonium chloride) significantly reduced free radical generation, p38 MAPK and ERK phosphorylation as well as NETs release, suggesting that p38 MAPK and ERK activation was downstream to free radical generation. The present study thus demonstrates ROS dependent activation of ERK and p38 MAPK, which mediated PMA induced NETs release from human neutrophils. J. Cell. Biochem. 114: 532–540, 2013. © 2012 Wiley Periodicals, Inc.     

Rab27a Is Essential for the Formation of Neutrophil Extracellular Traps (NETs) in Neutrophil-Like Differentiated HL60 Cells

Neutrophils play a crucial role in host defence. In response to a variety of inflammatory stimulation, they form neutrophil extracellular traps (NETs). NETs are extracellular structures composed of chromatin fibers decorated with antimicrobial proteins and developing studies indicate that NETs contribute to extracellular microbial killing. While the intracellular signaling pathways that regulate NET formation remain largely unknown, there is growing evidence that generation of reactive oxygen species (ROS) is a key event for NET formation. The Rab family small GTPase Rab27a is an important component of the secretory machinery of azurophilic granules in neutrophils. However, the precise mechanism of NET formation and whether or not Rab27a contributes to this process are unknown. Using neutrophil-like differentiated HL60 cells, we show here that Rab27a plays an essential role in both phorbol myristate acetate (PMA)- and Candida albicans-induced NET formation by regulating ROS production. Rab27a-knockdown inhibited ROS-positive phagosome formation during complement-mediated phagocytosis. To investigate the role of Rab27a in neutrophil function in detail, both primary human neutrophils and neutrophil-like differentiated HL60 cells were treated with PMA, and NET formation process was assessed by measurement of release of histone H3 into the medium, citrullination of the arginine in position 3 of histone H4 and chase of the nuclear change of the living cells in the co-existence of both cell-permeable and -impermeable nuclear indicators. PMA-induced NET formation occured sequentially in both neutrophil-like differentiated HL60 cells and primary neutrophils, and Rab27a-knockdown clearly inhibited NET formation in association with reduced ROS production. We also found that serum-treated Candida albicans triggers NET formation in a ROS-dependent manner, and that Rab27a-knockdown inhibits this process as well. Our findings demonstrate that Rab27a plays an important role in NET formation induced by both Candida albicans infection and PMA treatment by regulating ROS production.     

Oscillation of Reactive Oxygen Species Released by Activated Neutrophils

Phagocytic leukocytes, such as neutrophils and macrophages release reactive oxygen species (ROS) to the surrounding medium upon appropriate stimulation as part of their cytocidal activity. The release of ROS by inflammatory neutrophils, obtained by peritoneal injection of 12% caseinate-PBS was measured by the reduction of ferricytochrome c and luminol chemiluminescence (LCL). Neutrophils were harvested every 4 hours with cold PBS and stimulated with phorbol myristate acetate (PMA), formyl-methionyl-leucyl-phenylalanine (FMLP) or opsonized zymosan (OZ). On a regimen providing light between 6:00 to 18:00, PMA-stimulated neutrophils (1.0 x 10 7 neutrophil/ml) were found to release twice as much superoxide anion at night as they did during the day (clock time; 2:00 = 1.43 nmol/min vs. clock time 14:00 = 0.65 nmol/min). Neither FMLP- nor OZ-stimulated neutrophils displayed similar fluctuations. Thus, the qualitative and quantitative aspects of ROS generation by activated neutrophils differ significantly from one ligand to another. These results suggest that the effect of neutrophils on microorganisms and the surrounding tissues may differ with the nature of the stimulus and the time the stimulus is given.     

Oscillation of Reactive Oxygen Species Released by Activated Neutrophils

Phagocytic leukocytes, such as neutrophils and macrophages release reactive oxygen species (ROS) to the surrounding medium upon appropriate stimulation as part of their cytocidal activity. The release of ROS by inflammatory neutrophils, obtained by peritoneal injection of 12% caseinate-PBS was measured by the reduction of ferricytochrome c and luminol chemiluminescence (LCL). Neutrophils were harvested every 4 hours with cold PBS and stimulated with phorbol myristate acetate (PMA), formyl-methionyl-leucyl-phenylalanine (FMLP) or opsonized zymosan (OZ). On a regimen providing light between 6:00 to 18:00, PMA-stimulated neutrophils (1.0 x 10 7 neutrophil/ml) were found to release twice as much superoxide anion at night as they did during the day (clock time; 2:00 = 1.43 nmol/min vs. clock time 14:00 = 0.65 nmol/min). Neither FMLP- nor OZ-stimulated neutrophils displayed similar fluctuations. Thus, the qualitative and quantitative aspects of ROS generation by activated neutrophils differ significantly from one ligand to another. These results suggest that the effect of neutrophils on microorganisms and the surrounding tissues may differ with the nature of the stimulus and the time the stimulus is given.     

The Extracellular Matrix of Candida albicans Biofilms Impairs Formation of Neutrophil Extracellular Traps

Neutrophils release extracellular traps (NETs) in response to planktonic C. albicans. These complexes composed of DNA, histones, and proteins inhibit Candida growth and dissemination. Considering the resilience of Candida biofilms to host defenses, we examined the neutrophil response to C. albicans during biofilm growth. In contrast to planktonic C. albicans, biofilms triggered negligible release of NETs. Time lapse imaging confirmed the impairment in NET release and revealed neutrophils adhering to hyphae and migrating on the biofilm. NET inhibition depended on an intact extracellular biofilm matrix as physical or genetic disruption of this component resulted in NET release. Biofilm inhibition of NETosis could not be overcome by protein kinase C activation via phorbol myristate acetate (PMA) and was associated with suppression of neutrophil reactive oxygen species (ROS) production. The degree of impaired NET release correlated with resistance to neutrophil attack. The clinical relevance of the role for extracellular matrix in diminishing NET production was corroborated in vivo using a rat catheter model. The C. albicans pmr1Δ/Δ, defective in production of matrix mannan, appeared to elicit a greater abundance of NETs by scanning electron microscopy imaging, which correlated with a decreased fungal burden. Together, these findings show that C. albicans biofilms impair neutrophil response through an inhibitory pathway induced by the extracellular matrix.     

Quantitative analysis of hemin-induced neutrophil extracellular trap formation and effects of hydrogen peroxide on this phenomenon

Formation of neutrophil extracellular traps (NETs) can perpetuate sterile inflammation; thus, it is important to clarify their pathophysiological characteristics. Free heme, derived via hemolysis, is a major contributor to organ damage, and reportedly induces neutrophil activation as well as reactive oxygen species (ROS) production and NET formation. For this study, we examined hemin (Fe³⁺ -protoporphyrin IX)-induced NET formation quantitatively in vitro as well as the effects of oxidative stress.NETs formed in vitro from cultured neutrophils were quantitatively detected by using nuclease treatment and Sytox Green, a nucleic acid stain. Hemin-induced NET production was found to be in a dose-dependent manner, NADPH oxidase-dependent and toll-like receptor (TLR)-4 independent. Additionally, the iron molecule in the porphyrin ring was considered essential for the formation of NETs. In the presence of low concentrations of hydrogen peroxide, low concentrations of hemin-induced NETs were enhanced, unlike those of phorbol myristate acetate (PMA)-induced NETs.Quantitative analysis of NET formation may prove to be a useful tool for investigating NET physiology, and hemin could function as a possible therapeutic target for hemolysis-related events.     

Cytokines Induced Neutrophil Extracellular Traps Formation: Implication for the Inflammatory Disease Condition

Neutrophils (PMNs) and cytokines have a critical role to play in host defense and systemic inflammatory response syndrome (SIRS). Neutrophil extracellular traps (NETs) have been shown to extracellularly kill pathogens, and inflammatory potential of NETs has been shown. Microbial killing inside the phagosomes or by NETs is mediated by reactive oxygen and nitrogen species (ROS/RNS). The present study was undertaken to assess circulating NETs contents and frequency of NETs generation by isolated PMNs from SIRS patients. These patients displayed significant augmentation in the circulating myeloperoxidase (MPO) activity and DNA content, while PMA stimulated PMNs from these patients, generated more free radicals and NETs. Plasma obtained from SIRS patients, if added to the PMNs isolated from healthy subjects, enhanced NETs release and free radical formation. Expressions of inflammatory cytokines (IL-1β, TNFα and IL-8) in the PMNs as well as their circulating levels were significantly augmented in SIRS subjects. Treatment of neutrophils from healthy subjects with TNFα, IL-1β, or IL-8 enhanced free radicals generation and NETs formation, which was mediated through the activation of NADPH oxidase and MPO. Pre-incubation of plasma from SIRS with TNFα, IL-1β, or IL-8 antibodies reduced the NETs release. Role of IL-1β, TNFα and IL-8 thus seems to be involved in the enhanced release of NETs in SIRS subjects.     

Influences of chloride and hypochlorite on neutrophil extracellular trap formation

Background

The release by neutrophils of DNA-based extracellular traps (NETs) is a recently recognized innate immune phenomenon that contributes significantly to control of bacterial pathogens at tissue foci of infection. NETs have also been implicated in the pathogenesis of non-infectious diseases such as small vessel vasculitis, lupus and cystic fibrosis lung disease. Reactive oxygen species (ROS) are important mediators of NET generation (NETosis). Neutrophils with reduced ROS production, such as those from patients with chronic granulomatous disease or myeloperoxidase (MPO) deficiency, produce fewer NETs in response to inflammatory stimuli. To better understand the roles of various ROS in NETosis, we explore the role of MPO, its substrates chloride ion (Cl⁻) and hydrogen peroxide (H₂O₂), and its product hypochlorite (HOCl) in NETosis.

Findings

In human peripheral blood neutrophils, pharmacologic inhibition of MPO decreased NETosis. Absence of extracellular Cl⁻, a substrate for MPO, also reduced NETosis. While exogenous addition of H₂O₂ and HOCl stimulated NETosis, only exogenous HOCl could rescue NETosis in the setting of MPO inhibition. Neither pharmacological inhibition nor genetic deletion of MPO in murine neutrophils blocked NETosis, in contrast to findings in human neutrophils.

Conclusions

Our results pinpoint HOCl as the key ROS involved in human NETosis. This finding has implications for understanding innate immune function in diseases in which Cl⁻ homeostasis is disturbed, such as cystic fibrosis. Our results also reveal an example of significant species-specific differences in NET phenotypes, and the need for caution in extrapolation to humans from studies of murine NETosis.     

Effect of isorhapontigenin on respiratory burst of rat neutrophils

The effect of Isorhapontigenin (Iso) isolated from Belamcanda chinensis on respiratory burst of rat neutrophils was investigated. Iso (1, 10, 100 mmol/l) showed an inhibitory effect on superoxide anion and hydrogen peroxide production in phorbol myristate acetate (PMA) activated rat neutrophils in a concentration-dependent manner. Scanning electron microscopy detected that Iso (100 mmol/l) protected against surface changes in rat neutrophils stimulated with PMA. Also, 100 mmol/l Iso inhibited the release of beta-glucuronidase from the activated neutrophils. Electron-spin resonance (ESR) detected that Iso scavenged oxygen free radicals generated in the PMA activated Neutrophils. These results suggest that Iso inhibits respiratory burst of PMA-activated rat neutrophils by scavenging oxygen free radicals.     

Impaired neutrophil extracellular trap formation: a novel defect in the innate immune system of aged individuals

Neutrophil extracellular traps (NETs) are a recently discovered addition to the defensive armamentarium of neutrophils, assisting in the immune response against rapidly dividing bacteria. Although older adults are more susceptible to such infections, no study has examined whether aging in humans influences NET formation. We report that TNF‐α‐primed neutrophils generate significantly more NETs than unprimed neutrophils and that lipopolysaccharide (LPS)‐ and interleukin‐8 (IL‐8)‐induced NET formation exhibits a significant age‐related decline. NET formation requires generation of reactive oxygen species (ROS), and this was also reduced in neutrophils from older donors identifying a mechanism for reduced NET formation. Expression of IL‐8 receptors (CXCR1 and CXCR2) and the LPS receptor TLR4 was similar on neutrophils from young and old subjects, and neutrophils challenged with phorbol‐12‐myristate‐13‐acetate (PMA) showed no age‐associated differences in ROS or NET production. Taken together, these data suggest a defect in proximal signalling underlies the age‐related decline in NET and ROS generation. TNF‐α priming involves signalling through p38 MAP kinase, but activation kinetics were comparable in neutrophils from young and old donors. In a clinical setting, we assessed the capacity of neutrophils from young and older patients with chronic periodontitis to generate NETs in response to PMA and hypochlorous acid (HOCL). Neutrophil extracellular trap generation to HOCL, but not PMA, was lower in older periodontitis patients but not in comparison with age‐matched controls. Impaired NET formation is thus a novel defect of innate immunity in older adults but does not appear to contribute to the increased incidence of periodontitis in older adults.