Activation of nuclear factor kappa B by diesel exhaust particles in mouse epidermal cells through phosphatidylinositol 3-kinase/Akt signaling pathway

Unraveling the skin; a comprehensive review of atopic dermatitis, current understanding, and approaches

Atopic dermatitis, also known as atopic eczema, is a chronic inflammatory skin disease characterized by red pruritic skin lesions, xerosis, ichthyosis, and skin pain. Among the social impacts of atopic dermatitis are difficulties and detachment in relationships and social stigmatization. Additionally, atopic dermatitis is known to cause sleep disturbance, anxiety, hyperactivity, and depression. Although the pathological process behind atopic dermatitis is not fully known, it appears to be a combination of epidermal barrier dysfunction and immune dysregulation. Skin is the largest organ of the human body which acts as a mechanical barrier to toxins and UV light and a natural barrier against water loss. Both functions face significant challenges due to atopic dermatitis. The list of factors that can potentially trigger or contribute to atopic dermatitis is extensive, ranging from genetic factors, family history, dietary choices, immune triggers, and environmental factors. Consequently, prevention, early clinical diagnosis, and effective treatment may be the only resolutions to combat this burdensome disease. Ensuring safe and targeted drug delivery to the skin layers, without reaching the systemic circulation is a promising option raised by nano-delivery systems in dermatology. In this review, we explored the current understanding and approaches of atopic dermatitis and outlined a range of the most recent therapeutics and dosage forms brought by nanotechnology. This review was conducted using PubMed, Google Scholar, and ScienceDirect databases.

Air Pollution and Atopic Dermatitis, from Molecular Mechanisms to Population-Level Evidence: A Review

Atopic dermatitis (AD) has increased in prevalence to become the most common inflammatory skin condition globally, and geographic variation and migration studies suggest an important role for environmental triggers. Air pollution, especially due to industrialization and wildfires, may contribute to the development and exacerbation of AD. We provide a comprehensive, multidisciplinary review of existing molecular and epidemiologic studies on the associations of air pollutants and AD symptoms, prevalence, incidence, severity, and clinic visits. Cell and animal studies demonstrated that air pollutants contribute to AD symptoms and disease by activating the aryl hydrocarbon receptor pathway, promoting oxidative stress, initiating a proinflammatory response, and disrupting the skin barrier function. Epidemiologic studies overall report that air pollution is associated with AD among both children and adults, though the results are not consistent among cross-sectional studies. Studies on healthcare use for AD found positive correlations between medical visits for AD and air pollutants. As the air quality worsens in many areas globally, it is important to recognize how this can increase the risk for AD, to be aware of the increased demand for AD-related medical care, and to understand how to counsel patients regarding their skin health. Further research is needed to develop treatments that prevent or mitigate air pollution-related AD symptoms.

Carbonaceous Nanoparticle Air Pollution: Toxicity and Detection in Biological Samples

Among the different air pollutants, particulate matter (PM) is of great concern due to its abundant presence in the atmosphere, which results in adverse effects on the environment and human health. The different components of PM can be classified based on their physicochemical properties. Carbonaceous particles (CPs) constitute a major fraction of ultrafine PM and have the most harmful effects. Herein, we present a detailed overview of the main components of CPs, e.g., carbon black (CB), black carbon (BC), and brown carbon (BrC), from natural and anthropogenic sources. The emission sources and the adverse effects of CPs on the environment and human health are discussed. Particularly, we provide a detailed overview of the reported toxic effects of CPs in the human body, such as respiratory effects, cardiovascular effects, neurodegenerative effects, carcinogenic effects, etc. In addition, we also discuss the challenges faced by and limitations of the available analytical techniques for the qualitative and quantitative detection of CPs in atmospheric and biological samples. Considering the heterogeneous nature of CPs and biological samples, a detailed overview of different analytical techniques for the detection of CPs in (real-exposure) biological samples is also provided. This review provides useful insights into the classification, toxicity, and detection of CPs in biological samples.

Association of Wildfire Air Pollution and Health Care Use for Atopic Dermatitis and Itch

IMPORTANCE

Air pollution is a worldwide public health issue that has been exacerbated by recent wildfires, but the relationship between wildfire-associated air pollution and inflammatory skin diseases is unknown.

OBJECTIVE

To assess the associations between wildfire-associated air pollution and clinic visits for atopic dermatitis (AD) or itch and prescribed medications for AD management.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional time-series study assessed the associations of air pollution resulting from the California Camp Fire in November 2018 and 8049 dermatology clinic visits (4147 patients) at an academic tertiary care hospital system in San Francisco, 175 miles from the wildfire source. Participants included pediatric and adult patients with AD or itch from before, during, and after the time of the fire (October 2018 through February 2019), compared with those with visits in the same time frame of 2015 and 2016, when no large wildfires were near San Francisco. Data analysis was conducted from November 1, 2019, to May 30, 2020.

EXPOSURES

Wildfire-associated air pollution was characterized using 3 metrics: fire status, concentration of particulate matter less than 2.5 μm in diameter (PM2.5), and satellite-based smoke plume density scores.

MAIN OUTCOMES AND MEASURES

Weekly clinic visit counts for AD or itch were the primary outcomes. Secondary outcomes were weekly numbers of topical and systemic medications prescribed for AD in adults.

RESULTS

Visits corresponding to a total of 4147 patients (mean [SD] age, 44.6 [21.1] years; 2322 [56%] female) were analyzed. The rates of visits for AD during the Camp Fire for pediatric patients were 1.49 (95% CI, 1.07-2.07) and for adult patients were 1.15 (95% CI, 1.02-1.30) times the rate for nonfire weeks at lag 0, adjusted for temperature, relative humidity, patient age, and total patient volume at the clinics for pediatric patients. The adjusted rate ratios for itch clinic visits during the wildfire weeks were 1.82 (95% CI, 1.20-2.78) for the pediatric patients and 1.29 (95% CI, 0.96-1.75) for adult patients. A 10-μg/m3 increase in weekly mean PM2.5 concentration was associated with a 7.7% (95% CI, 1.9%-13.7%) increase in weekly pediatric itch clinic visits. The adjusted rate ratio for prescribed systemic medications in adults during the Camp Fire at lag 0 was 1.45 (95% CI, 1.03-2.05).

CONCLUSIONS AND RELEVANCE

This cross-sectional study found that short-term exposure to air pollution due to the wildfire was associated with increased health care use for patients with AD and itch. These results may provide a better understanding of the association between poor air quality and skin health and guide health care professionals' counseling of patients with skin disease and public health practice.

Combined Toxicity of Metal Nanoparticles: Comparison of Individual and Mixture Particles Effect

Toxicity of metal nanoparticles (NPs) are closely associated with increasing intracellular reactive oxygen species (ROS) and the levels of pro-inflammatory mediators. However, NP interactions and surface complexation reactions alter the original toxicity of individual NPs. To date, toxicity studies on NPs have mostly been focused on individual NPs instead of the combination of several species. It is expected that the amount of industrial and highway-acquired NPs released into the environment will further increase in the near future. This raises the possibility that various types of NPs could be found in the same medium, thereby, the adverse effects of each NP either could be potentiated, inhibited or remain unaffected by the presence of the other NPs. After uptake of NPs into the human body from various routes, protein kinases pathways mediate their toxicities. In this context, family of mitogen-activated protein kinases (MAPKs) is mostly efficient. Despite each NP activates almost the same metabolic pathways, the toxicity induced by a single type of NP is different than the case of co-exposure to the combined NPs. The scantiness of toxicological data on NPs combinations displays difficulties to determine, if there is any risk associated with exposure to combined nanomaterials. Currently, in addition to mathematical analysis (Response surface methodology; RSM), the quantitative-structure-activity relationship (QSAR) is used to estimate the toxicity of various metal oxide NPs based on their physicochemical properties and levels applied. In this chapter, it is discussed whether the coexistence of multiple metal NPs alter the original toxicity of individual NP. Additionally, in the part of "Toxicity of diesel emission/exhaust particles (DEP)", the known individual toxicity of metal NPs within the DEP is compared with the data regarding toxicity of total DEP mixture.

The role of xenobiotics in triggering psoriasis

Psoriasis is a common inflammatory skin disease affecting approximately 2% of the world population. A complex interplay of genetic predisposition and risk factors contributes to the risk of its onset. Several xenobiotics have been implicated in the pathogenesis of psoriasis. Drugs are among the most investigated trigger factors; strong association with disease induction or exacerbation has been reported for β-blockers, lithium, NSAIDs and ACE inhibitors, all of which are commonly used in the management of various comorbidities in psoriasis patients. Furthermore, inhibitors of TNF have a well-documented potential for triggering new-onset psoriasis when used for other indications (e.g. Crohn's disease or rheumatoid arthritis), while post-marketing data have revealed the same association for ustekinumab. Several other drugs have been connected with psoriasis, but the evidence is less compelling. Smoking and alcohol have been reported to increase the risk for occurrence of psoriasis, but can also affect unfavorably the course of the disease and its response to treatment. Furthermore, exposure to secondhand smoke, especially in childhood, also mediates the risk. Emerging data now suggest that air pollution also has a detrimental effect on skin disease, including psoriasis, but this association needs further investigation. Understanding of the toxic effect of xenobiotics on the initiation and clinical course of psoriasis can contribute to its better control, as it can help with the avoidance of triggering factors and, in some cases, influence the success of pharmacological treatment. It, therefore, has an important place in the comprehensive management of psoriasis.

Impact of airborne particulate matter on skin: a systematic review from epidemiology to in vitro studies

BACKGROUND

Air pollution is killing close to 5 million people a year, and harming billions more. Air pollution levels remain extremely high in many parts of the world, and air pollution-associated premature deaths have been reported for urbanized areas, particularly linked to the presence of airborne nano-sized and ultrafine particles.

MAIN TEXT

To date, most of the research studies did focus on the adverse effects of air pollution on the human cardiovascular and respiratory systems. Although the skin is in direct contact with air pollutants, their damaging effects on the skin are still under investigation. Epidemiological data suggested a correlation between exposure to air pollutants and aggravation of symptoms of chronic immunological skin diseases. In this study, a systematic literature review was conducted to understand the current knowledge on the effects of airborne particulate matter on human skin. It aims at providing a deeper understanding of the interactions between air pollutants and skin to further assess their potential risks for human health.

CONCLUSION

Particulate matter was shown to induce a skin barrier dysfunction and provoke the formation of reactive oxygen species through direct and indirect mechanisms, leading to oxidative stress and induced activation of the inflammatory cascade in human skin. Moreover, a positive correlation was reported between extrinsic aging and atopic eczema relative risk with increasing particulate matter exposure.

Ambient air pollution and the hospital outpatient visits for eczema and dermatitis in Beijing: a time-stratified case-crossover analysis

BACKGROUND

Eczema and dermatitis are a group of common skin conditions with multiple risk factors. Evidence of the effects of air pollutants on eczema and dermatitis remains limited. This study aimed to investigate the effects of short-term exposure to air pollution on eczema and dermatitis in Beijing.

METHODS

A time-stratified case-crossover design was used to assess the associations between short-term changes in air pollution and the hospital outpatient visits for eczema and dermatitis in Beijing.

RESULTS

A total of 157 595 outpatient visits for eczema and dermatitis were recorded from April 1, 2012 to April 30, 2014. All pollutants showed significant positive associations with the number of outpatient visits for eczema and dermatitis on lag 0 (the current day). Per IQR increase in PM2.5, PM10, NO2 and SO2 was associated with 3.81% (95% CI: 2.92-4.7%), 3.18% (95% CI: 2.39-3.97%), 5.43% (95% CI: 4.43-6.43%) and 5.57% (95% CI: 4.55-6.58%) increases in outpatient visits for eczema and dermatitis on lag 0. Associations of air pollutants with eczema and dermatitis outpatient visits varied with the seasons and were stronger among older people and females. Also, an association of consecutive days' high concentration pollution with increased outpatient visits was observed.

CONCLUSIONS

Exposure to air pollution increases the exacerbation of eczema and dermatitis and stronger positive associations between air pollutants and outpatient visits for eczema and dermatitis were found among the aged, females and when high concentration air pollution occurs continuously.

Ambient endotoxin in PM10 and association with inflammatory activity, air pollutants, and meteorology, in Chitwan, Nepal

BACKGROUND

Endotoxin associated with ambient PM (particulate matter) has been linked to adverse respiratory symptoms, but there have been few studies of ambient endotoxin and its association with co-pollutants and inflammation.

OBJECTIVES

Our aim was to measure endotoxin associated with ambient PM₁₀ (particulate matter with aerodynamic diameter<10μm) in summer 2016 at four locations in Chitwan, Nepal, and investigate its association with meteorology, co-pollutants, and inflammatory activity.

METHODS

PM₁₀ concentrations were recorded and filter paper samples were collected using E-samplers; PM_1, PM_2.5, black carbon (BC), methane (CH₄), and carbon monoxide (CO) were also measured. The Limulus amebocyte lysate (LAL) assay was used for endotoxin quantification and the nuclear factor kappa B (NFκB) activation assay to assess inflammatory activity.

RESULTS

The mean concentration of PM₁₀ at the different locations ranged from 136 to 189μg/m³, and of endotoxin from 0.29 to 0.53EU/m³. Pollutant presence was positively correlated with endotoxin. Apart from relative humidity, meteorological variations had no significant impact on endotoxin concentration. NF-κB activity was negatively correlated with endotoxin concentration.

CONCLUSIONS

To the best of our knowledge, this study provides the first measurements of ambient endotoxin associated with PM₁₀ in Nepal. Endotoxin and co-pollutants were positively associated indicating a similar source. Endotoxin was negatively correlated with inflammatory activity as a result of a time-limited forest fire event during the sampling period. Studies of co-pollutants suggested that the higher levels of endotoxin related to biomass burning were accompanied by increased levels of anti-inflammatory agents, which suppressed the endotoxin inflammatory effect.

Association of Short-Term Exposure to Ambient Fine Particulate Matter with Skin Symptoms in Schoolchildren: A Panel Study in a Rural Area of Western Japan

Numerous studies have unmasked the deleterious effects of particulate matter less than 2.5 μm (PM_2.5) on health. However, epidemiologic evidence focusing on the effects of PM_2.5 on skin health remains limited. An important aspect of Asian dust (AD) in relationship to health is the amount of PM_2.5 contained therein. Several studies have demonstrated that AD can aggravate skin symptoms. The current study aimed to investigate the effects of short-term exposure to PM_2.5 and AD particles on skin symptoms in schoolchildren. A total of 339 children recorded daily skin symptom scores during February 2015. Light detection and ranging were used to calculate AD particle size. Generalized estimating equation logistic regression analyses were used to estimate the associations among skin symptoms and the daily levels of PM_2.5 and AD particles. Increases in the levels of PM_2.5 and AD particles were not related to an increased risk of skin symptom events, with increases of 10.1 μg/m³ in PM_2.5 and 0.01 km^-1 in AD particles changing odds ratios by 1.03 and 0.99, respectively. These results suggest that short-term exposure to PM_2.5 and AD does not impact skin symptoms in schoolchildren.

Diesel Exhaust Particles Upregulate Interleukins IL-6 and IL-8 in Nasal Fibroblasts

Background

Diesel exhaust particles (DEP) are a major source of air pollution. Nasal fibroblasts are known to produce various cytokines and chemokines. The aim of this study was to evaluate DEP-induced cytokines and chemokines in nasal fibroblasts and to identify the signaling pathway involved.

Methods

A cytokine and chemokine array performed after stimulation of nasal fibroblasts with DEP revealed that levels of IL-6 and IL-8 were increased most significantly among various cytokines and chemokines. RT—PCR and ELISA were used to determine the mRNA and protein expression levels of IL-6 and IL-8. Signaling pathways of p-38, Akt, and NF-κB were analyzed by western blotting, luciferase assay, and ELISA. Organ cultures of nasal interior turbinate were also developed to demonstrate the ex vivo effect of DEP on the expression of IL-6 and IL-8 and the associated signaling pathway.

Results

DEP increased the expressions of IL-6 and IL-8 in nasal fibroblasts at mRNA and protein levels. DEP induced phosphorylation of p38, Akt, and NF-κB, whereas inhibitors of p38, Akt, and NF-κB blocked these phophorylations and the expressions of IL-6 and IL-8. These findings were also observed in ex vivo organ culture of nasal inferior turbinate.

Conclusions

DEP induces expression of IL-6 and IL-8 via p38, Akt, and NF-κB signaling pathways in nasal fibroblasts. This finding suggests that air pollution might induce or aggravate allergic rhinitis or chronic rhinosinusitis.

Recognizing the impact of ambient air pollution on skin health

Ambient air pollution is a known public health hazard that negatively impacts non-cutaneous organs; however, our knowledge regarding the effects on skin remains limited. Current scientific evidence suggests there are four mechanisms by which ambient air pollutants cause adverse effects on skin health: (i) generation of free radicals, (ii) induction of inflammatory cascade and subsequent impairment of skin barrier, (iii) activation of the aryl hydrocarbon receptor (AhR) and (iv) alterations to skin microflora. In this review, we provide a comprehensive overview on ambient air pollutants and their relevant sources, and highlight current evidence of the effects on skin.

Effects of diesel exhaust particles on microRNA-21 in human bronchial epithelial cells and potential carcinogenic mechanisms

Air pollution plays a role in cancer risk, particularly in lung cancer, which is the leading cause of cancer-related mortality worldwide. Diesel exhaust particles (DEPs), a component of diesel exhaust products, is a complex mixture of particle compounds that include a large number of known and suspected human carcinogens. Historically, lung cancer, which is associated with DEPs, has been the focus of attention as a health risk in human and animal studies. However, the mechanism by which DEPs cause lung cancer remains unclear. The present study reports that DEPs increased miR-21 expression and then activated the PTEN/PI3K/AKT pathway in human bronchial epithelial (HBE) cells, which may serve as an important carcinogenic mechanism. However, the data revealed that short-term exposure to a high DEP concentration did not cause evident cell carcinogenesis in HBE cells.

Toxicology of ambient particulate matter

It is becoming increasingly clear that inhalation exposure to particulate matter (PM) can lead to or exacerbate various diseases, which are not limited to the lung but extend to the cardiovascular system and possibly other organs and tissues. Epidemiological studies have provided strong evidence for associations with chronic obstructive pulmonary disease (COPD), asthma, bronchitis and cardiovascular disease, while the evidence for a link with lung cancer is less strong. Novel research has provided first hints that exposure to PM might lead to diabetes and central nervous system (CNS) pathology. In the current review, an overview is presented of the toxicological basis for adverse health effects that have been linked to PM inhalation. Oxidative stress and inflammation are discussed as central processes driving adverse effects; in addition, profibrotic and allergic processes are implicated in PM-related diseases. Effects of PM on key cell types considered as regulators of inflammatory, fibrotic and allergic mechanisms are described.

Effects of ultrafine petrol exhaust particles on cytotoxicity, oxidative stress generation, DNA damage and inflammation in human A549 lung cells and murine RAW 264.7 macrophages

Air pollution has persistently been the major cause of respiratory-related illness and death. Environmental pollutants such as diesel and petrol exhaust particles (PEPs) are the major contributors to urban air pollution. The aim of the present study was to characterize and investigate the in vitro cytotoxicity, oxidative stress, DNA damage and inflammation induced by PEPs. Cultured type II epithelium cells (human A549 lung cells) and alveolar macrophages (murine RAW 264.7 cells) were exposed to control, vehicle control and to different concentrations of PEPs for up to 24h. Each treatment was evaluated by cell viability, cytotoxicity, oxidative stress, DNA damage and inflammatory parameters. Overall in vitro studies demonstrated that both cell lines showed similar patterns in response to the above studies induced by petrol exhaust nanoparticles (PENPs). Vehicle control showed no changes compared with the control. In both cell lines, significant changes at the dose of 20 and 50μg/mL (A549 cell lines) and 10and 20μg/mL (macrophages) for PENPs were found. The reactive oxygen species production in both cell lines shot up in minutes, reached the maximum within an hour and came down after 4h. Hence, exposure to PENPs resulted in dose-dependent toxicity in cultured A549 cells and RAW 264.7 cells and was closely correlated to increased oxidative stress, DNA damage and inflammation.

Diesel exhaust particles modify natural killer cell function and cytokine release

Background

Natural killer (NK) cells are an important lymphocyte population in the nasal mucosa and play important roles in linking the innate and the adaptive immune response. Their two main functions are direct cell-mediated cytotoxicity and the release of cytokines. They are important during viral infections and cancer. Due to their location in the nasal mucosa, NK cells are likely exposed to inhaled pollutants, such as diesel exhaust. Whether and how exposure to diesel exhaust particles (DEP) affects NK cell function in the context of viral infections has not been investigated.

Methods

NK cells were isolated from peripheral blood obtained from normal healthy volunteers and subsequently stimulated with the viral mimetic polyinosinic:polycytidylic acid (pI:C), DEP, or pI:C+DEP for 18 hours. NK cells were subsequently analyzed for changes in surface marker expression, cytokine production, gene expression changes, and cytotoxic function using flow cytometry, ELISA, qRT-PCR, and cell-mediated cytotoxicity assay, respectively.

Results

Stimulation of NK cells with pI:C and pI:C+DEP, but not DEP alone, increased the release of IL-1β, IL-2, IL-4, IL-8, IL-10, IL-12p70, IFN-γ and TNF-α. As compared to pI:C alone or pI:C+DEP, the release of IL-1β, IL-8 and TNF-α was significantly lower after DEP stimulation alone. Stimulation with pI:C alone increased the gene and protein expression of granzyme B and perforin, which was completely blunted by adding DEP. Addition of DEP further reduced CD16 expression in pI:C stimulated cells. Similarly, cell-mediated cytotoxicity was significantly reduced by the addition of DEP.

Conclusions

In the context of viral infection, DEP potentially reduces NK cells' ability to kill virus-infected host cells, in spite of normal cytokine levels, and this may increase susceptibility to viral infections . This reduction in the potential ability of NK cells to kill virus-infected host cells may increase the susceptibility to viral infections after DEP exposure.

Glutathione-S-transferase M1 regulation of diesel exhaust particle-induced pro-inflammatory mediator expression in normal human bronchial epithelial cells

Background

Diesel exhaust particles (DEP) contribute substantially to ambient particulate matter (PM) air pollution in urban areas. Inhalation of PM has been associated with increased incidence of lung disease in susceptible populations. We have demonstrated that the glutathione S-transferase M1 (GSTM1) null genotype could aggravate DEP-induced airway inflammation in human subjects. Given the critical role airway epithelial cells play in the pathogenesis of airway inflammation, we established the GSTM1 deficiency condition in primary bronchial epithelial cells from human volunteers with GSTM1 sufficient genotype (GSTM1+) using GSTM1 shRNA to determine whether GSTM1 deficiency could exaggerate DEP-induced expression of interleukin-8 (IL-8) and IL-1β proteins. Furthermore, the mechanisms underlying GSTM1 regulation of DEP-induced IL-8 and IL-1β expression were also investigated.

Methods

IL-8 and IL-1β protein levels were measured using enzyme-linked immunosorbent assay. GSTM1 deficiency in primary human bronchial epithelial cells was achieved using lentiviral GSTM1 shRNA particles and verified using real-time polymerase chain reaction and immunoblotting. Intracellular reactive oxygen species (ROS) production was evaluated using flow cytometry. Phosphorylation of protein kinases was detected using immunoblotting.

Results

Exposure of primary human bronchial epithelial cells (GSTM1+) to 25-100 μg/ml DEP for 24 h significantly increased IL-8 and IL-1β protein expression. Knockdown of GSTM1 in these cells further elevated DEP-induced IL-8 and IL-1β expression, implying that GSTM1 deficiency aggravated DEP-induced pro-inflammatory response. DEP stimulation induced the phosphorylation of extracellular signal-regulated kinase (ERK) and Akt, the downstream kinase of phosphoinositide 3-kinase (PI3K), in GSTM1+ bronchial epithelial cells. Pharmacological inhibition of ERK kinase and PI3K activity blocked DEP-induced IL-8 and IL-1β expression. DEP-induced ERK and Akt phosphorylation could be increased by GSTM1 knockdown. In addition, pretreatment of HBEC with the antioxidant N-acetyl cysteine significantly inhibited DEP-induced ERK and Akt phosphorylation, and subsequent IL-8 and IL-1β expression.

Conclusion

GSTM1 regulates DEP-induced IL-8 and IL-1β expression in primary human bronchial epithelial cells by modulation of ROS, ERK and Akt signaling.

Urban particulate matter activates Akt in human lung cells

The normally picturesque Cache Valley in northern Utah is frequently reported to have the worst particulate (PM) air pollution in the United States. Numerous epidemiological studies conducted elsewhere have associated PM exposure to a variety of cardiovascular diseases and early mortality. We have previously shown that Cache Valley PM (CVPM) is pro-inflammatory, through a variety of mechanisms involving the release of inflammatory cytokines, unfolded protein response, ER stress, and C-reactive protein (CRP). This study was undertaken to determine whether Cache Valley PM (CVPM) would activate Akt, an upstream mechanism common to these events. Human lung (BEAS-2B) cells were treated with either fine (PM(2.5)) or coarse (PM(10)) particles (12.5 and 25 μg/ml) for periods up to 24 h. PM-exposed cells exhibited Akt activation as evidenced by phosphorylation at Thr(308) and Ser(473). Events downstream of Akt activation such as NF-κB activation were observed at 1 and 24 h, but IκB phosphorylation occurred only at 24 h, indicating that mechanisms of PM-mediated NF-κB activation are time dependent. Akt and NF-κB related inflammatory cytokine IL-1α, and IL-6 and the chemokine IL-8 were upregulated in treated cells at 6 and 24 h. The calpain inhibitor leupeptin limited Akt phosphorylation to Ser(473) and reduced release of IL-1α, IL-6, and IL-8, indicating that calpain or similar protease(s) are involved in PM-induced activation of Akt and subsequent release of inflammatory cytokines. Our data indicate that PM activates Akt, which may play a role in the pro-inflammatory response to PM exposure.

CagA(+) H. pylori induces Akt1 phosphorylation and inhibits transcription of p21(WAF1/CIP1) and p27(KIP1) via PI3K/Akt1 pathway

OBJECTIVE

Cytotoxin-associated protein (CagA) of H. pylori has been confirmed to be closely associated with gastric inflammation and tumorigenesis, but the mechanism behind it is little understood. In this study, we try to determine roles of CagA(+) strain in activating PI3K/Akt1 signaling pathway, and affecting expression of p21(WAF1/CIP1) and p27(KIP1), and also in releasing IL-8 in host cells.

METHODS

Akt1 phosphorylation and IL-8 levels of CagA(+) and CagA⁻ strain infected AGS cells were detected by ELISAs. Two quantitative RT-PCRs were established to measure p21(WAF1/CIP1) and p27(KIP1) mRNA levels in the CagA(+) and CagA⁻ strain infected cells. LY294002, an inhibitor of PI3K/Akt pathway, was used to define effect of the pathway in IL-8 release.

RESULTS

CagA(+) strain could induce an obvious elevation of Akt1 phosphorylation in the infected AGS cells while CagA? strain failed to do so. The CagA(+) H. pylori strain infected AGS cells showed significant drops both in p21(WAF1/CIP1) and p27(KIP1) mRNA levels, whereas the CagA⁻ H. pylori strain caused a remarkable increase in p21(WAF1/CIP1) mRNA without affecting p27(KIP1) gene transcription in the AGS cells. Both the CagA(+) and CagA⁻ H. pylori strains enabled AGS cells to produce close elevated levels of IL-8, and the LY294002 block resulted in unexpected elevations of IL-8 levels.

CONCLUSIONS

CagA can activate PI3K/Akt1 pathway that plays an inhibitory role in IL-8 release in H. pylori infected AGS cells. Activation of PI3K/Akt1 pathway and subsequent negative regulation of p21(WAF1/CIP1) and p27(KIP1) expression might be involved in CagA-associated carcinogenesis.

Evodiamine-induced human melanoma A375-S2 cell death was mediated by PI3K/Akt/caspase and Fas-L/NF-kappaB signaling pathways and augmented by ubiquitin-proteasome inhibition

Evodiamine, a major alkaloidal component of Evodiae fructus exhibits anti-tumor activities. We have previously reported that evodiamine has a marked inhibitory effect on IL-1 sensitive human melanoma A375-S2 cells proliferation, and this action might be through inactivation of PI3K signaling. However, the detailed molecular mechanisms of evodiamine-induced cell death remains poorly understood. In present study, we further confirmed that Akt is the main effector molecule involved in this pathway. Evodiamine also led to IkappaBalpha phosphorylation and degradation that reflect translocation of NF-kappaB. Pretreatment of A375-S2 cells with ubiquitin-proteasome inhibitor MG132 was shown to aggregate the evodiamine caused cell death at 24h. In addition, MG132 reduced ERK phosphorylation, increased caspase-3 activation, Fas-L expression and Bcl-2 cleavage in evodiamine-treated A375-S2 cells. These results suggested the PI3K/Akt/caspase and Fas-L/NF-kappaB signaling pathways might account for the responses of A375-S2 cell death induced by evodiamine, and these signals could be augmented by ubiquitin-proteasome pathway.

Ultraviolet B regulation of transcription factor families: roles of nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1) in UVB-induced skin carcinogenesis

Prolonged and repeated exposure of the skin to ultraviolet light (UV) leads not only to aging of the skin but also increases the incidence of non-melanoma skin cancer (NMSC). Damage of cells induced by ultraviolet B (UVB) light both at the DNA level and molecular level initiates the activation of transcription factor pathways, which in turn regulate the expression of a number of genes termed the "UV response genes". Two such transcription factor families that are activated in this way are those of the nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) families. These two transcription factor families have been identified to be involved in the processes of cell proliferation, cell differentiation and cell survival and therefore play important roles in tumorigenesis. The study of these two transcription factor pathways and the cross-talk between them in response to UVB exposure may help with the development of new chemopreventive strategies for the prevention of UVB-induced skin carcinogenesis.

Antioxidant enzyme induction: a new protective approach against the adverse effects of diesel exhaust particles

Exposure to airborne particulate pollutants such as diesel exhaust particles (DEPs) has been associated with allergic respiratory disorders, including asthma and allergic rhinitis. In this communication, we review recent advances in the mechanism by which DEPs elicit their harmful effects and the protective role of antioxidants. Reactive oxidative species (ROS) are believed to play a key role in cellular damage after exposure to DEPs. Numerous reports demonstrate that both proinflammatory and anti-inflammatory products are induced by DEPs via the activation of transcription factors. DEPs trigger multiple signaling pathways, which lead to DNA damage and cell apoptosis, inflammatory response, and antioxidant defense. Recent studies both in vitro and in mice show that antioxidants could alleviate the allergic inflammatory effects of DEPs. Human in vivo models suggest that the important phase II enzymes GSTM1 and GSTP1 modify the adjuvant effect of diesel exhaust particles on allergic inflammation. We have shown that the induction of phase II enzymes by the chemical sulforaphane can block DEP-induced enhanced immunoglobulin (Ig) E production in B cells and DEP-induced proinflammatory cytokine production in epithelial cells. These findings suggest that overexpression of antioxidant enzymes could constitute a powerful potential chemopreventive approach against adverse effects induced by oxidant pollutants such as DEPs.

Signal transduction in Alzheimer disease: p21-activated kinase signaling requires C-terminal cleavage of APP at Asp664

The deficits in Alzheimer disease (AD) stem at least partly from neurotoxic beta-amyloid peptides generated from the amyloid precursor protein (APP). APP may also be cleaved intracellularly at Asp664 to yield a second neurotoxic peptide, C31. Previously, we showed that cleavage of APP at the C-terminus is required for the impairments seen in APP transgenic mice, by comparing elements of the disease in animals modeling AD, with (platelet-derived growth factor B-chain promoter-driven APP transgenic mice; PDAPP) versus without (PDAPP D664A) a functional Asp664 caspase cleavage site. However, the signaling mechanism(s) by which Asp664 contributes to these deficits remains to be elucidated. In this study, we identify a kinase protein, recently shown to bind APP at the C-terminus and to contribute to AD, whose activity is modified in PDAPP mice, but normalized in PDAPP D664A mice. Specifically, we observed a significant increase in nuclear p21-activated kinase (isoforms 1, 2, and or 3; PAK-1/2/3) activation in hippocampus of 3 month old PDAPP mice compared with non-transgenic littermates, an effect completely prevented in PDAPP D664A mice. In contrast, 13 month old PDAPP mice displayed a significant decrease in PAK-1/2/3 activity, which was once again absent in PDAPP D664A mice. Similarly, in hippocampus of early and severe AD subjects, there was a progressive and subcellular-specific reduction in active PAK-1/2/3 compared with normal controls. Interestingly, total PAK-1/2/3 protein was increased in early AD subjects, but declined in moderate AD and declined further, to significantly below that of control levels, in severe AD. These findings are compatible with previous suggestions that PAK may be involved in the pathophysiology of AD, and demonstrate that both early activation and late inactivation in the murine AD model require the cleavage of APP at Asp664.

The role of glycogen synthase kinase 3beta in the transformation of epidermal cells

Glycogen synthase kinase 3beta (GSK3beta) is a multifunctional serine/threonine kinase. We showed that the expression of GSK3beta was drastically down-regulated in human cutaneous squamous cell carcinomas and basal cell carcinomas. Due to its negative regulation of many oncogenic proteins, we hypothesized that GSK3beta may function as a tumor suppressor during the neoplastic transformation of epidermal cells. We tested this hypothesis using an in vitro model system, JB6 mouse epidermal cells. In response to epidermal growth factor (EGF) or 12-O-tetradecanoylphorbol-13-acetate (TPA), the promotion-sensitive JB6 P+ cells initiate neoplastic transformation, whereas the promotion-resistant JB6 P- cells do not. JB6 P- cells expressed much higher levels of GSK3beta than JB6 P+ cells; JB7 cells, the transformed derivatives of JB6, had the least amount of GSK3beta. The activity of GSK3beta is negatively regulated by its phosphorylation at Ser9. EGF and TPA induced strong Ser9 phoshorylation in JB6 P+ cells, but phosphorylation was seen at a much lesser extent in JB6 P- cells. EGF and TPA-stimulated Ser9 phosphorylation was mediated by phosphoinositide-3-kinase (PI3K)/Akt and protein kinase C (PKC) pathways. Inhibition of GSK3beta activation significantly stimulated activator protein-1 (AP-1) activity. Overexpression of wild-type (WT) and S9A mutant GSK3beta in JB6 P+ cells suppressed EGF and TPA-mediated anchorage-independent growth in soft agar and tumorigenicity in nude mice. Overexpression of a kinase-deficient (K85R) GSK3beta, in contrast, potentiated anchorage-independent growth and drastically enhanced in vivo tumorigenicity. Together, these results indicate that GSK3beta plays an important role in skin tumorigenesis.

Health effects of airborne particulate matter: do we know enough to consider regulating specific particle types or sources?

Researchers and regulators have often considered preferentially regulating the types of ambient airborne particulate matter (PM) most relevant to human health effects. While few would argue the inherent merits of such a policy, many believe there may not yet be enough information to differentially regulate PM species. New evidence, using increasingly sophisticated methodologies, has become available in the last several years, allowing more accurate assessment of exposure and resultant associations with specific types of PM, or PM derived from different sources. Such new studies may also allow differentiation of effects from different chemical components in the same study against the same health endpoints. This article considers whether this new evidence might be adequate to allow us to "speciate" PM types or sources by severity of health effects. We address this issue with respect to two widespread sources of PM, emissions from motor vehicles and coal-fired power plants. Emissions from less widespread sources, residual oil and steel/coking facilities, are also discussed in order to illustrate how health effects associated with such emissions might instead be associated with more widespread sources when accurate exposure information is unavailable. Based upon evaluation of studies and methodologies which appear to contain the most accurate information on exposure and response to important emissions, including variable local emissions, it is concluded that public health will likely be better protected by reduction of various vehicular emissions than by continued regulation of the total mass of fine PM (PM <2.5 microm, or PM2.5) as if all PM in this mode is equitoxic. However, the knowledge base is incomplete. Important remaining research questions are identified.

Benzo[a]pyrene-dependent activation of transcription factors NF-κB and AP-1 related to tumor promotion in hepatoma cell cultures

The activation by the carcinogenic polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (BP) of transcription factors NF-kappaB and AP-1 in hepatoma 27 and HepG2 cell cultures was studied. In contrast to the hepatoma HepG2 cells, cytochrome P450 isoforms and Ah-receptor are not expressed in the hepatoma 27 cells. The transcription factor NF-kappaB was activated only in the hepatoma 27 cells by BP treatment but not by its noncarcinogenic isomer benzo[e]pyrene (BeP). Conversely to NF-kappaB activation the transcription factor AP-1 was activated in the hepatoma HepG2 cells by cell treatment with BP but not in the hepatoma 27 cells. It is concluded that the NF-kappaB activation is caused by nonmetabolized BP molecule and not related to activation of the Ah-receptor. The transcription factor AP-1 seems to be activated as a result of the interaction of BP with the Ah-receptor. The realization of tumor promotion stage by carcinogenic PAHs treatment in dependence on the cytochrome P450 and Ah-receptor levels in the initiated cells is discussed.

An environmental quinoid polycyclic aromatic hydrocarbon, acenaphthenequinone, modulates cyclooxygenase-2 expression through reactive oxygen species generation and nuclear factor kappa B activation in A549 cells

Diesel exhaust particles (DEPs) contain oxygen-containing polycyclic aromatic hydrocarbons (PAHs) called quinoid PAHs. Some quinoid PAHs generate free radicals as they undergo enzymatic and nonenzymatic redox cycling with their corresponding semiquinone radicals. Reactive oxygen species (ROS) produced by these reactions can cause severe oxidative stress connected with inflammatory processing. Although humans and animals are continuously exposed to these chemicals in the environment, little is known about which quinoid PAHs are active. In this study, we estimated the intracellular ROS production and nuclear factor kappa B (NF-kappaB) translocation in A549 cells exposed to isomers of quinoid PAHs having two to four rings. We found that both acenaphthenequinone (AcQ) and 9,10-phenanthrenequinone (PQ) enhanced ROS generation and that AcQ translocated NF-kappaB from the cytosol to the nucleus. However, PQ, which has been reported to induce apoptosis, did not influence NF-kappaB activation. In addition, AcQ induced cyclooxygenase-2 (COX-2) expression which is a key enzyme in the inflammatory processing involved in the activation of NF-kappaB. Upregulation of NF-kappaB and COX-2 expression by AcQ treatment was suppressed by the antioxidant N-acetylcysteine (NAC). These results provide that AcQ might play an important role in human lung inflammatory diseases as an air pollutant.

MMP-2 mediates ethanol-induced invasion of mammary epithelial cells over-expressing ErbB2

Ethanol is a tumor promoter and may enhance the metastasis of breast cancer. We have previously demonstrated that over-expression of ErbB2 promoted ethanol-mediated invasion of mammary epithelial cells and breast cancer cells. However, the underlying cellular/molecular mechanisms remain unknown. By gelatin zymography, we showed that over-expression of ErbB2 increased the production of matrix metalloproteinase-2 (MMP-2) and MMP-9 in human mammary epithelial cells (HB2). Transient or stable transfection of ErbB2 cDNA to HB2 cells upregulated the transcripts and the activity of the MMP-2/-9 gene promoter; the upregulation of MMP-2/-9 expression was mediated by p38 mitogen-activated protein kinase (p38 MAPK) and phosphatidylinositol 3-kinase (PI3K). Although ethanol, at physiologically relevant concentrations (100-400 mg/dl), did not affect the production of MMP-2/-9, it activated MMP-2 in HB2 cells over-expressing ErbB2 (HB2(ErbB2)), but not HB2 cells; it enhanced the cleavage of proform MMP-2 (72 kDa) to an active form (62 kDa). The activation was dependent on c-jun N-terminal kinases (JNKs) and reactive oxygen species (ROS). On the other hand, ethanol affected neither the expression nor the activation of MMP-9. Selective inhibitors of MMP-2 (SB-3CT and OA-Hy) and antioxidants significantly inhibited ethanol-stimulated invasion of HB2(ErbB2) cells. Furthermore, knocking down MMP-2 by small interference RNA also induced a partial blockage on ethanol-promoted invasion of HB2(ErbB2) cells. Thus, ethanol-stimulated invasion of cells over-expressing ErbB2 was mediated, at least partially, by MMP-2 activation.

Diesel exhaust enhances virus- and poly(I:C)-induced Toll-like receptor 3 expression and signaling in respiratory epithelial cells

Prior exposure of respiratory epithelial cells to an aqueous-trapped solution of diesel exhaust (DE(as)) enhances the susceptibility to influenza infections. Here, we examined the effect of DE(as) on the Toll-like receptor 3 (TLR3) pathway, which is responsible for the recognition of and response to viruses and double-stranded RNA. Flow cytometric and confocal microscopy analyses showed that TLR3 is predominantly expressed in the cytoplasm of respiratory epithelial cells. To examine the effect of DE on TLR3 expression and function, differentiated human bronchial or nasal epithelial cells as well as A549 cells were exposed to DE(as) and then infected with influenza A or treated with polyriboinosinic acid-polyribocytidylic acid [poly(I:C)], a synthetic form of double-stranded RNA. Exposure to DE(as) before infection with influenza or stimulation with poly(I:C) significantly upregulated the expression of TLR3. Additionally, preexposure to DE(as) significantly increased the poly(I:C)-induced expression of IL-6. Overexpression of a dominant-negative mutant form of TNF receptor-associated factor 6 reversed the effects of DE(as) on poly(I:C)-induced IL-6 expression, suggesting that the response was TLR3 dependent. Similarly, preexposure to DE(as) significantly increased nuclear levels of interferon regulatory factor 3 and the expression of IFN-beta in response to poly(I:C). Pretreatment with wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase, was able to abate the effect of DE(as) on poly(I:C)-induced IFN-beta expression. Together, these results indicate that exposure of respiratory epithelial cells to DE(as) could potentially alter the response to viral infections by increasing the expression and function of TLR3.