Nonspecific Host Defense Research Articles

Dried Chlorella powder supplementation: Impact on broiler chicken growth, health, and intestinal microflora

The use of dried Chlorella as an immune and growth stimulant to enhance nonspecific host defense mechanisms or as an antimicrobial to inhibit bacterial growth has been reported. This study aimed to assess the effects of dried Chlorella powder (DCP) supplementation on the growth, health, and intestinal microflora of commercial broiler chicks, comparing a diet containing DCP with an antibiotic-based diet. A total of 120 pieces day-old Cobb 500 broiler chicks were reared at Sher-e-Bangla Agricultural University Poultry Farm, Dhaka, and randomly divided into four experimental groups of three replicates each, with 10 chicks per replication. One group was fed a control diet, while the remaining three groups were fed diets with 0.5% and 1.0% DCP, and antibiotics, respectively. Results indicated significant (P<0.05) improvements in body weight and dressing percentage with DCP inclusion compared to control-fed broilers. A linear increase in body weight was observed with higher DCP levels, with birds on the 1% DCP diet achieving superior body weights (1665.13±8.82) compared to the control and antibiotic groups. Feed Conversion Ratio (FCR) and feed consumption were also significantly (P<0.05) improved, with the best FCR at 1% DCP (1.37±0.01) and the highest FCR in the control group (1.45±0.00). The highest feed consumption was noted in the control group. No significant (P>0.05) differences were observed in the relative weight of spleen and bursa among the groups. DCP had no significant (P>0.05) effects on liver, gizzard, intestine, and heart weights. Hematological studies revealed no significant (P>0.05) differences, except for Hemoglobin and Red Blood Cells (RBC), which were significantly (P<0.05) increased by DCP compared to control and antibiotic groups. DCP supplementation significantly (P<0.05) reduced E. coli and Salmonella sp. counts while increasing Lactobacillus sp. counts. Additionally, treatments with DCP significantly (P<0.05) boosted Newcastle disease (ND) titre levels compared to the control group. The study showed that DCP can be effectively replaced antibiotics in broiler diets, enhancing growth, health, and immune response, thereby promoting sustainable and safer poultry production practices.

SCARF Genes in COVID-19 and Kidney Disease: A Path to Comorbidity-Specific Therapies.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), which has killed ~7 million persons worldwide. Chronic kidney disease (CKD) is the most common risk factor for severe COVID-19 and one that most increases the risk of COVID-19-related death. Moreover, CKD increases the risk of acute kidney injury (AKI), and COVID-19 patients with AKI are at an increased risk of death. However, the molecular basis underlying this risk has not been well characterized. CKD patients are at increased risk of death from multiple infections, to which immune deficiency in non-specific host defenses may contribute. However, COVID-19-associated AKI has specific molecular features and CKD modulates the local (kidney) and systemic (lung, aorta) expression of host genes encoding coronavirus-associated receptors and factors (SCARFs), which SARS-CoV-2 hijacks to enter cells and replicate. We review the interaction between kidney disease and COVID-19, including the over 200 host genes that may influence the severity of COVID-19, and provide evidence suggesting that kidney disease may modulate the expression of SCARF genes and other key host genes involved in an effective adaptive defense against coronaviruses. Given the poor response of certain CKD populations (e.g., kidney transplant recipients) to SARS-CoV-2 vaccines and their suboptimal outcomes when infected, we propose a research agenda focusing on CKD to develop the concept of comorbidity-specific targeted therapeutic approaches to SARS-CoV-2 infection or to future coronavirus infections.

Activation of the complement system by nanoparticles and strategies for complement inhibition

The complement system is a multicomponent and multifunctional arm of the innate immune system. Complement contributes to non-specific host defence and maintains homeostasis through multifaceted processes and pathways, including crosstalk with the adaptive immune system, the contact (coagulation) and the kinin systems, and alarmin high-mobility group box 1. Complement is also present intracellularly, orchestrating a wide range of housekeeping and physiological processes in both immune and nonimmune cells, thus showing its more sophisticated roles beyond innate immunity, but its roles are still controversial. Particulate drug carriers and nanopharmaceuticals typically present architectures and surface patterns that trigger complement system in different ways, resulting in both beneficial and adverse responses depending on the extent of complement activation and regulation as well as pathophysiological circumstances. Here we consider the role of complement system and complement regulations in host defence and evaluate the mechanisms by which nanoparticles trigger and modulate complement responses. Effective strategies for the prevention of nanoparticle-mediated complement activation are introduced and discussed.

Host responses against the fish parasitizing ciliate Cryptocaryon irritans.

The parasitic ciliate Cryptocaryon irritans, which infects almost all marine fish species occurring in both tropical and subtropical regions throughout the world. The disease, cryptocaryonosis, accounts for significant economic losses to the aquaculture industry. This review attempts to provide a comprehensive overview of the biology of the parasite, host-parasite interactions and both specific and non-specific host defense mechanisms are responsible for the protection of fish against challenge infections with this ciliate. Also, this article reflects the current interest in this subject area and the quest to develop an available vaccine against the disease. Due to the high frequency of clinical fish cryptocaryonosis, the study of fish immune responses to C. irritans provides an optimal experimental model for understanding immunity against extracellular protozoa.

Nanometer- and angstrom-scale characteristics that modulate complement responses to nanoparticles.

The contribution of the complement system to non-specific host defence and maintenance of homeostasis is well appreciated. Many particulate systems trigger complement activation but the underlying mechanisms are still poorly understood. Activation of the complement cascade could lead to particle opsonisation by the cleavage products of the third complement protein and might promote inflammatory reactions. Antibody binding in a controlled manner and/or sensing of particles by the complement pattern-recognition molecules such as C1q and mannose-binding lectin can trigger complement activation. Particle curvature and spacing arrangement/periodicity of surface functional groups/ligands are two important parameters that modulate complement responses through multivalent engagement with and conformational regulation of surface-bound antibodies and complement pattern-recognition molecules. Thus, a better fundamental understanding of nanometer- and angstrom-scale parameters that modulate particle interaction with antibodies and complement proteins could portend new possibilities for engineering of particulate drug carriers and biomedical platforms with tuneable complement responses and is discussed here.

Activation of Innate Immunity and Autophagy in Brain Tissues with Prion Disease and Degradation of Abnormal PrPs in Cells - China's Studies.

Unlike infectious diseases caused by conventional microbes, there are no detectable specific humoral or cellular immunoresponses to prion infection. However, extensive and active gliosis is observable in affected brain regions along with significant deposits of scrapie-like prion protein (PrPSc). Here, we summarize our studies of vibrant activation of host non-specific immune components and autophagy in the microenvironment of prion infected brains. Activation of the brain’s innate immunity and autophagy upon prion infection reflect non-specific host defense systems attempt to dispose of accumulated prions. Vibrant elevation of neuroinflammation leads to neuron injury.

Formation of Protein Corona on Nanoparticle Affects Different Complement Activation Pathways Mediated by C1q.

As nanoparticles (NPs) are intravenously entering the bloodstream, proteins in the plasma can recognize and bind them to form a protein corona that affects how NPs are perceived by biological systems. The complement is an essential part of the innate immunity that contributes to non-specific host defense. How complement recognizes NPs has not been elucidated. Here, we developed a proteomics and biochemical approach to understand the applied risk of activated complement by NPs. Complement proteins absorbed on Hydroxyapatite Nanoparticles (HAP-NPs) and Silicon dioxide Nanoparticles (SiO2-NPs) were analyzed by proteomics with LC-MS. The effect of complement activation was studied by iC3b/Sc5b-9/C3a/C4a/C5a with ELISA. An inhibitory model was established via EDTA and EGTA to confirm the selective pathway activation of both NPs. Finally, the regulation of complement by NPs was analyzed by western blot. The results indicate that HAP-NPs start the activation of the complement through the classical pathway because of the absorption of C1q and the release of C1r/C1s. Meanwhile, the soluble regulatory molecules such as CFI, C4bp, and CFH tried to resist the complement system activation by the cleavage of C3 convertase. In contrast, SiO2-NPs can activate the alternative pathway of the complement through the absorption of CFD and CFB. It was clarified that HAP-NPs and SiO2-NPs activate complement through different mechanisms. These studies provide a scientific basis for the design and modification of nano-drug carriers for delaying their recognition and clearance by the mononuclear phagocytic system and simultaneously reducing the immunotoxicity of NPs. The understanding of protein corona is conducive to innovation in the field of "immune-safe-by-design" nanomedicines.

An assessment of the immune status of the children population as a marker of technogenic pollution of the environment

This article describes results of the immunological study of school-aged children residing in cities with different levels of the technogenic air pollution. Children from cities with the highest level of the technogenic pollution had a high number of immature neutrophils (band cells) and eosinophils. The children living in these ecologically unfavorable areas have presented a reduction of T-cell antigen receptor CD3, CD4, CD8, CD20, CD16, CD95. This indicates to that both T-cell and B-cell immunity is suppressed. The decline of the phagocytic function in neutrophils indicates to the suppression of the nonspecific host defense mechanisms also.

Synthetic avenues towards a tetrasaccharide related to Streptococcus pneumonia of serotype 6A.

Streptococcus pneumonia (SPn) is a Gram-positive bacterium which causes life threatening diseases. The bacteria protect themselves against non-specific host defence by an external polysaccharide (PS) capsule which bears a repeating unit, α-D-Galp(1->3)-α-D-Glcp(1->3)-α-L-Rhap(1->3)-D-Rib (SPn 6A). A closer look at the structure reveals the presence of α-linked galactose and glucose residues. The synthesis of these 1,2-cis glycosidic linkages are considered challenging particularly in the context of a one-pot oligosaccharide synthesis. We have synthesized the aforesaid tetrasaccharide (SPn 6A) based on both stepwise and sequential one-pot glycosylation reactions using easily accessible common building blocks; eventually similar overall yields were obtained in both cases.

The potential management of oral candidiasis using anti-biofilm therapies

Candida albicans is a minor component of the oral microbiota and an opportunistic pathogen that takes advantage of the immunocompromised host and causes oral mucositis and oral candidiasis. This organism is able to undergo phenotypic modification from a yeast to hyphae growth phase, one of the key arsenals for immune cell evasion, tissue invasion and biofilm formation. The latter property coupled with overgrowth and immune compromising factors such as HIV/AIDS, cancer treatments, organ transplantation, diabetes, corticosteroid use, dentures, and broad-spectrum antibiotic use have modified the fungus from a normal component of the microflora to a foe of an oral cavity and resulting in reduced sensitivity towards commonly utilised antifungal agents. Hence, the need for alternative therapy to curb this plight is of importance. Making use of biomolecules produced by Streptococcus mutans, application of lactoferrin which is a nonspecific host defense factor found in saliva with metal chelating and broader antimicrobial properties, use of probiotics which have the capacity to boost the host immunity through eliciting Immunoglobulin A synthesis, and perturbing the pathogen’s environment via competition of space and food, and application of photodynamic therapy can help to manage the burden of oral candidiasis.

Complement activation turnover on surfaces of nanoparticles

The complement system is an important component of the innate immune system, which contributes to non-specific host defence. Particulate matters, such as invading pathogens and nanomedicines, in the blood may activate the complement system through classical, lectin and alternative pathways. Complement activation can aid recognition and clearance of particulate matters by immune cells, but uncontrolled complement activation can inflict damage and be life threatening. Plasma proteins on adsorption to surfaces of nanoparticles also play a significant role in complement activation and particularly through the alternative pathway. This process is continuous and changeable in vivo; protein-complement complexes are formed on the nanoparticle surface and then released and the cycle repeats on further plasma protein deposition. This complement activation turnover poses a challenge for design of immune-safe nanomedicines.

Effects of dietary recombinant chlorella supplementation on growth performance, meat quality, blood characteristics, excreta microflora, and nutrient digestibility in broilers

The use of chlorella as an immune stimulant to enhance nonspecific host defense mechanisms or as an antimicrobial to inhibit bacterial growth has been reported. Thus, the aim of the present study was to clarify the effect of recombinant chlorella supplementation on growth performance, meat quality, and the blood profile, excreta microflora, and nutrient digestibility in broilers. A total of 375 one-day-old ROSS 308 broilers (male and female) were allotted to 5 dietary treatments using 5 cages with 15 chicks per cage. Treatments were: 1) NC, basal diet supplemented with 1.0% E. coli fermented liquor (EFL); 2) PC1, 0.2% EFL with chlorella; 3) PC2, 1.0% EFL with chlorella; 4) T1, 0.2% EFL with chlorella (anti-viral); and 5) T2, 1.0% EFL with chlorella (anti-viral). The broilers in the T2 treatment groups showed higher body weight gain (BGW) by 2.55% (P < 0.01) and lower feed conversion ratio (FCR) by 2.75% (P < 0.05) compared with those fed the control NC treatment group. Moreover, the blood contents of blood urea nitrogen (BUN), creatinine, and IgA in the broilers of the T2 treatment group were significantly increased by 28.12, 23.07, and 29.72%, respectively —more than those found in the broilers of the NC treatment group (P < 0.01). In contrast, the LDL/C in the blood from the animals in the T2 treatment group was significantly decreased by 23.23% — more than that in the blood from the NC broilers (P < 0.05). Based on these results, we suggest that the dietary supplementation of broilers with recombinant chlorella could improve their growth performance, increase the concentration of IgA and apparently metabolizable nitrogen in the blood, and decrease ammonia emissions. Therefore, our findings have important implications for the effect of recombinant chlorella supplementation through increasing the concentration of IgA and the level of metabolizable nitrogen.

Elevated nitric oxide in recurrent vulvovaginal candidiasis - association with clinical findings.

Recurrent vulvovaginal candidiasis is defined as having three to four episodes per year and causes substantial suffering. Little is known about the mechanisms leading to relapses in otherwise healthy women. Nitric oxide is part of the nonspecific host defense and is increased during inflammation. Nitric oxide levels were measured and the expression of inducible nitric oxide synthase was analyzed in the vagina during an acute episode of recurrent vulvovaginal candidiasis and after treatment with fluconazole. Twenty-eight women with symptoms of recurrent vulvovaginal candidiasis were enrolled together with 31 healthy controls. Nitric oxide was measured with an air-filled 25-mL silicon catheter balloon incubated in the vagina for five minutes and then analyzed by chemiluminescence technique. Vaginal biopsies were analyzed for the expression of inducible nitric oxide synthase. Symptoms and clinical findings were surveyed using a scoring system. The measurements and biopsies were repeated in patients after six weeks of fluconazole treatment. Nitric oxide levels were increased during acute infection (median 352ppb) compared with controls (median 6ppb), p<0.0001. The levels decreased after treatment (median 18ppb) but were still higher than in controls. Increased expression of inducible nitric oxide synthase was observed in the epithelial basal layer in patients before and after treatment compared with controls. Before treatment, there were positive correlations between nitric oxide and symptom (rs =0.644) and examination scores (rs =0.677), p<0.001. Nitric oxide is significantly elevated in patients with recurrent vulvovaginal candidiasis during acute episodes of infection and decreases after antifungal treatment. The results illustrate the pronounced inflammatory response in recurrent vulvovaginal candidiasis correlating to symptoms of pain and discomfort.

A proteomic analysis of the iron response of Photobacterium damselae subsp. damselae reveals metabolic adaptations to iron levels changes and novel potential virulence factors

Photobacterium damselae subsp. damselae (Pdd) is a marine bacterium that can infect numerous species of marine fish as well as other species including humans. Low iron availability is one of the signs that bacterial pathogens can detect in order to begin colonizing their host, and the reduction of iron levels is a nonspecific host defense strategy that prevents bacterial proliferation. In this work a proteomic approach was used to study the gene expression adaptations of a Pdd strain in response to iron availability. A comparative analysis of induced proteins in both high- and low-iron conditions showed profound cellular metabolic adaptations that result, for instance, in amino acid requirement. It also provided important information about the changes that occur in the energetic metabolism induced by the surrounding iron levels, allowing for the identification of novel potential virulence factors. Among others, genes involved in the synthesis and transport of a vibrioferrin-like siderophore were identified for the first time. In addition to plasmid pPHDD1-encoded Dly and HlyA hemolysins, a pPHDD1-borne operon, which may encode a transferrin receptor, was also found. This operon identification suggests that this virulence plasmid could encode so-far unknown additional virulence factors other than hemolysins.

State of Nonspecific Host Defense in Patients with Pyoinflammatory Diseases of Soft Tissues and Its Correction by Photomodification

The results of research of performance factors of nonspecific defense of 116 patients with acute purulent inflammation of soft tissues were analyzed. The regularities of these parameters inhibition were detected depending on the severity of the inflammatory process. The use of the ultraviolet and laser radiation equally stimulates increase in the levels of factors of nonspecific host defense and promotes positive course of the disease.

Innate immune regulation by STAT-mediated transcriptional mechanisms.

The term innate immunity typically refers to a quick but non-specific host defense response against invading pathogens. The innate immune system comprises particular immune cell populations, epithelial barriers, and numerous secretory mediators including cytokines, chemokines, and defense peptides. Innate immune cells are also now recognized to play important contributing roles in cancer and pathological inflammatory conditions. Innate immunity relies on rapid signal transduction elicited upon pathogen recognition via pattern recognition receptors (PRRs) and cell:cell communication conducted by soluble mediators, including cytokines. A majority of cytokines involved in innate immune signaling use a molecular cascade encompassing receptor-associated Jak protein tyrosine kinases and STAT (signal transducer and activator of transcription) transcriptional regulators. Here, we focus on roles for STAT proteins in three major innate immune subsets: neutrophils, macrophages, and dendritic cells (DCs). While knowledge in this area is only now emerging, understanding the molecular regulation of these cell types is necessary for developing new approaches to treat human disorders such as inflammatory conditions, autoimmunity, and cancer.

Skin Electroporation of a Plasmid Encoding hCAP-18/LL-37 Host Defense Peptide Promotes Wound Healing

Host defense peptides, in particular LL-37, are emerging as potential therapeutics for promoting wound healing and inhibiting bacterial growth. However, effective delivery of the LL-37 peptide remains limiting. We hypothesized that skin-targeted electroporation of a plasmid encoding hCAP-18/LL-37 would promote the healing of wounds. The plasmid was efficiently delivered to full-thickness skin wounds by electroporation and it induced expression of LL-37 in the epithelium. It significantly accelerated reepithelialization of nondiabetic and diabetic wounds and caused a significant VEGFa and interleukin (IL)-6 induction. IL-6 was involved in LL-37-mediated keratinocyte migration in vitro and IL-6 neutralizing antibodies delivered to mice were able to suppress the wound healing activity of the hCAP-18/LL-37 plasmid. In a hindlimb ischemia model, electroporation of the hCAP-18/LL-37 plasmid increased blood perfusion, reduced muscular atrophy, and upregulated the angiogenic chemokines VEGFa and SDF-1a, and their receptors VEGF-R and CXCR-4. These findings demonstrate that a localized gene therapy with LL-37 is a promising approach for the treatment of wounds.

How to use C-reactive protein in acute coronary care

C-reactive protein is an acute phase protein and an established marker for detection, risk stratification, and monitoring of infections and inflammatory and necrotic processes. Because C-reactive protein is sensitive but not specific, its values must be interpreted in the clinical context. In patients with acute myocardial infarction (AMI), C-reactive protein increases within 4–6 h of symptoms, peaks 2–4 days later, and returns to baseline after 7–10 days.1 C-reactive protein has gained interest recently as a marker for risk stratification in acute coronary syndrome (ACS) when measured by high-sensitivity C-reactive protein assays. These assays have greater analytical sensitivity and reliably measure C-reactive protein concentrations within the reference range with low imprecision (5–10%).2 Because of evidence that atherosclerosis is an inflammatory disease, high-sensitivity C-reactive protein can be used as a biomarker of risk in primary prevention and in patients with known cardiovascular disease.3 The aim of this review is to evaluate the use of C-reactive protein in patients with acute coronary disease. C-reactive protein is a non-specific first-line host defence mechanism.4 With stimulation by cytokines (e.g. interleukins and tumour necrosis factor-alpha), C-reactive protein synthesis in hepatocytes occurs within 4–6 h. Concentrations can rise 1000-fold or more over 24–48 h. C-reactive protein has been detected in atherosclerotic plaques; its possible role in atherosclerogenesis is summarized in Figure 1 , but is still a matter of debate.5 Genetic variants account for 35–40% of the variability in high-sensitivity C-reactive protein.6 Figure 1 Possible pathophysiological effects of C-reactive protein in atherosclerosis. Aggregated C-reactive protein selectively binds LDL and VLDL in serum, thereby potentially participating in the mechanisms involved in plaque formation and destabilization, and shows some of the key properties of antibodies and may contribute to immune responses by activation of antigen presenting cells. Procoagulant effects have been reported in vitro as …

BUTYRATE-MEDIATED GENOMIC CHANGES INVOLVED IN NON-SPECIFIC HOST DEFENSES, MATRIX REMODELING AND THE IMMUNE RESPONSE IN THE RUMEN EPITHELIUM OF COWS AFFLICTED WITH SUBACUTE RUMINAL ACIDOSIS

Subacute Ruminal Acidosis (SARA) is a disorder in cattle which can lead to chronic inflammation in the rumen epithelium, known as rumenitis. Butyrate has been shown to attenuate some of the detrimental effects of inflammatory gastroenteral disorders but the molecular mechanisms mediated by butyrate have not been defined. The objective of this study was to define the inflammatory-related genomic changes responsible for the beneficial effects of butyrate. Experimentally, 16 fistulated dairy cows at mid-lactation were fed a SARA-inducing (45% non-fiber carbohydrate) diet beginning 2 days before the beginning of treatment and continuing throughout the experiment. Cows were then evenly divided into treatment groups where a carrier with (n = 8) or without (n = 8) supplemental butyrate (2.5% initial DM intake) was deposited into the rumen daily for 7 days. The minimum rumen pH was higher in cows with supplemental butyrate (4.96±0.09 to 5.20±0.05, p = 0.040), but mean pH, maximum pH and the duration for which rumen pH was below 5.6 was unaffected. Free plasma Lipopolysaccharide (LPS) concentration was unaffected by treatment as was the concentration of Serum Amyloid A (SAA), although the LPS Binding Protein (LBP) concentration was increased by the addition of butyrate to the rumen (6.91±0.29 to 7.93±0.29 µg mL-1, p = 0.024). Of the rumen Short Chain Fatty Acids (SCFA) tested, only butyrate showed a pronounced treatment effect, rising from 8.60±0.94 to 21.60±0.94 mM (p≤0.0001). Plasma Beta-Hydroxybutyrate (BHBA) concentration also increased (799.50±265.24 to 3261.63±265.24 µM, p≤0.001). Butyrate infusion did not affect milk parameters (total fat, lactose, total protein and LOS); however, when related to dry matter intake, milk production efficiency was increased (p = 0.035). Microarray and qRT-PCR analyses of rumen papillae biopsies collected on day 7 found that butyrate administration affected (p≤0.05) the expression of genes involved in Non-Specific Host Defense (NSHD), Remodeling or adaptation (RM) and Immune Response (IR). Of the 49 genes tested by qRT-PCR, 9 (LCN2, MMP1, MUC16, GPX2, CSTA, FUT1, SERPINE2, BCAM, RAC3) were upregulated, 20 (MTOR, AKIRIN2, NFKBIZ, NFKB2, ACVR2A, LAMB1, FRS2, PPARD, LBP, NEDD4L, SGK1, DEDD2, MAP3K8, PARD6B, PLIN2, ADA, HPGD, FMO5, BMP6, TCHH) were downregulated and 20 were unchanged due to butyrate administration in the proximal gastrointestinal tract. These results demonstrate the potential protective effect and molecular mechanisms involved in a novel butyrate treatment for inflammatory gastrointestinal conditions.

Crotonaldehyde induces apoptosis in alveolar macrophages through intracellular calcium, mitochondria and p53 signaling pathways

Crotonaldehyde, a highly electrophilic α, β-unsaturated aldehyde, is a ubiquitous environmental pollutant and a risk factor for multiple respiratory diseases. Crotonaldehyde is highly volatile and hydrophilic, so it is efficiently absorbed in the respiratory tract. Alveolar macrophages are major effector cells of the nonspecific host defence in the lung. The aim of this study was to investigate the molecular mechanisms and signaling pathways responsible for cell death of alveolar macrophage induced by crotonaldehyde. Our results show that crotonaldehyde induces apoptosis in alveolar macrophages, as indicated by phosphatidylserine externalization and DNA fragmentation. Pretreatment of alveolar macrophages with N-acetylcysteine, ascorbic acid, α-tocopherol, superoxide dismutase inhibited crotonaldehyde-induced apoptosis. Crotonaldehyde-induced apoptosis was characterized by ROS generation, GSH depletion, loss of mitochondrial membrane potential (ΔΨm), the release of cytochrome c from mitochondria, caspase-3/7 and caspase-9 activation, elevation of intracellular Ca(2+) concentration and the increase of p53 expression. Furthermore, pretreatment with either p53 inhibitor pifithrin-α or calcium chelator BAPTA-AM effectively attenuated apoptosis induced by crotonaldehyde. Taken together, our results showed that crotonaldehyde induce apoptosis in alveolar macrophages through intracellular calcium, mitochondria and p53 signaling pathways. These results would help to illustrate the mechanism of toxicity induced by crotonaldehyde and to look for a novel treatment for diseases induced by exposure to crotonaldehyde-rich pollutants such as cigarette smoke.