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Biomass Smoke Exposure Enhances Rhinovirus-Induced Inflammation in Primary Lung Fibroblasts

View Article: PubMed Central - PubMed

ABSTRACT

Biomass smoke is one of the major air pollutants and contributors of household air pollution worldwide. More than 3 billion people use biomass fuels for cooking and heating, while other sources of exposure are from the occurrence of bushfires and occupational conditions. Persistent biomass smoke exposure has been associated with acute lower respiratory infection (ALRI) as a major environmental risk factor. Children under the age of five years are the most susceptible in developing severe ALRI, which accounts for 940,000 deaths globally. Around 90% of cases are attributed to viral infections, such as influenza, adenovirus, and rhinovirus. Although several epidemiological studies have generated substantial evidence of the association of biomass smoke and respiratory infections, the underlying mechanism is still unknown. Using an in vitro model, primary human lung fibroblasts were stimulated with biomass smoke extract (BME), specifically investigating hardwood and softwood types, and human rhinovirus-16 for 24 h. Production of pro-inflammatory mediators, such as IL-6 and IL-8, were measured via ELISA. Firstly, we found that hardwood and softwood smoke extract (1%) up-regulate IL-6 and IL-8 release (p ≤ 0.05). In addition, human rhinovirus-16 further increased biomass smoke-induced IL-8 in fibroblasts, in comparison to the two stimulatory agents alone. We also investigated the effect of biomass smoke on viral susceptibility by measuring viral load, and found no significant changes between BME exposed and non-exposed infected fibroblasts. Activated signaling pathways for IL-6 and IL-8 production by BME stimulation were examined using signaling pathway inhibitors. p38 MAPK inhibitor SB239063 significantly attenuated IL-6 and IL-8 release the most (p ≤ 0.05). This study demonstrated that biomass smoke can modulate rhinovirus-induced inflammation during infection, which can alter the severity of the disease. The mechanism by which biomass smoke exposure increases inflammation in the lungs can be targeted and inhibited via p38 MAP kinase pathway.

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The effects of ERK (A), SMAD (B), and p38 MAP kinase (C) inhibitors on IL-6 production by hardwood and softwood smoke extract. Primary human lung fibroblasts (n = 4) were pretreated for an hour with signaling inhibitors, PD98059 (10 µM), SB431542 (10 µM), and SB239063 (3 µM) in DMSO (vehicle control) for ERK, SMAD, and p38 MAP kinase pathway, respectively, then stimulated with 1% hardwood and softwood smoke extract for 24 h. Supernatant was collected and IL-6 concentration analysis was executed via ELISA. Data are expressed as the percent of inhibition from control and bars represent mean ± SEM. Statistical analysis was executed by using repeated measures, one-way ANOVA with Tukey’s post-test. Significance is represented as * p < 0.05.
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ijms-17-01403-f006: The effects of ERK (A), SMAD (B), and p38 MAP kinase (C) inhibitors on IL-6 production by hardwood and softwood smoke extract. Primary human lung fibroblasts (n = 4) were pretreated for an hour with signaling inhibitors, PD98059 (10 µM), SB431542 (10 µM), and SB239063 (3 µM) in DMSO (vehicle control) for ERK, SMAD, and p38 MAP kinase pathway, respectively, then stimulated with 1% hardwood and softwood smoke extract for 24 h. Supernatant was collected and IL-6 concentration analysis was executed via ELISA. Data are expressed as the percent of inhibition from control and bars represent mean ± SEM. Statistical analysis was executed by using repeated measures, one-way ANOVA with Tukey’s post-test. Significance is represented as * p < 0.05.

Mentions: There are different potential signaling pathways being activated by biomass smoke to induce IL-6 and IL-8 production. PI3 kinase, ERK, SMAD, p38 MAP kinase, NFκB, JNK and COX signaling pathways have all been previously shown to play a role in up-regulating inflammation from oxidative stimuli such as cigarette smoke. To examine this, chemical inhibitors were used, which are specific to the signaling pathways mentioned above. PI3 kinase, NFκB, JNK, and COX inhibitors were unable to attenuate IL-6 and IL-8 production from both hardwood and softwood smoke extract stimulation (data not shown). Softwood smoke-induced IL-6 and IL-8 was significantly attenuated by p38 MAP kinase inhibitor (Figure 6 and Figure 7). In addition, softwood smoke-induced IL-8 was also inhibited by ERK and SMAD inhibitors (Figure 7). Surprisingly, hardwood smoke-induced IL-6 was not inhibited by any of the signaling inhibitors used (Figure 6), however, hardwood smoke-induced IL-8 solely involved p38 MAP kinase pathway (Figure 7).


Biomass Smoke Exposure Enhances Rhinovirus-Induced Inflammation in Primary Lung Fibroblasts
The effects of ERK (A), SMAD (B), and p38 MAP kinase (C) inhibitors on IL-6 production by hardwood and softwood smoke extract. Primary human lung fibroblasts (n = 4) were pretreated for an hour with signaling inhibitors, PD98059 (10 µM), SB431542 (10 µM), and SB239063 (3 µM) in DMSO (vehicle control) for ERK, SMAD, and p38 MAP kinase pathway, respectively, then stimulated with 1% hardwood and softwood smoke extract for 24 h. Supernatant was collected and IL-6 concentration analysis was executed via ELISA. Data are expressed as the percent of inhibition from control and bars represent mean ± SEM. Statistical analysis was executed by using repeated measures, one-way ANOVA with Tukey’s post-test. Significance is represented as * p < 0.05.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5037683&req=5

ijms-17-01403-f006: The effects of ERK (A), SMAD (B), and p38 MAP kinase (C) inhibitors on IL-6 production by hardwood and softwood smoke extract. Primary human lung fibroblasts (n = 4) were pretreated for an hour with signaling inhibitors, PD98059 (10 µM), SB431542 (10 µM), and SB239063 (3 µM) in DMSO (vehicle control) for ERK, SMAD, and p38 MAP kinase pathway, respectively, then stimulated with 1% hardwood and softwood smoke extract for 24 h. Supernatant was collected and IL-6 concentration analysis was executed via ELISA. Data are expressed as the percent of inhibition from control and bars represent mean ± SEM. Statistical analysis was executed by using repeated measures, one-way ANOVA with Tukey’s post-test. Significance is represented as * p < 0.05.
Mentions: There are different potential signaling pathways being activated by biomass smoke to induce IL-6 and IL-8 production. PI3 kinase, ERK, SMAD, p38 MAP kinase, NFκB, JNK and COX signaling pathways have all been previously shown to play a role in up-regulating inflammation from oxidative stimuli such as cigarette smoke. To examine this, chemical inhibitors were used, which are specific to the signaling pathways mentioned above. PI3 kinase, NFκB, JNK, and COX inhibitors were unable to attenuate IL-6 and IL-8 production from both hardwood and softwood smoke extract stimulation (data not shown). Softwood smoke-induced IL-6 and IL-8 was significantly attenuated by p38 MAP kinase inhibitor (Figure 6 and Figure 7). In addition, softwood smoke-induced IL-8 was also inhibited by ERK and SMAD inhibitors (Figure 7). Surprisingly, hardwood smoke-induced IL-6 was not inhibited by any of the signaling inhibitors used (Figure 6), however, hardwood smoke-induced IL-8 solely involved p38 MAP kinase pathway (Figure 7).

View Article: PubMed Central - PubMed

ABSTRACT

Biomass smoke is one of the major air pollutants and contributors of household air pollution worldwide. More than 3 billion people use biomass fuels for cooking and heating, while other sources of exposure are from the occurrence of bushfires and occupational conditions. Persistent biomass smoke exposure has been associated with acute lower respiratory infection (ALRI) as a major environmental risk factor. Children under the age of five years are the most susceptible in developing severe ALRI, which accounts for 940,000 deaths globally. Around 90% of cases are attributed to viral infections, such as influenza, adenovirus, and rhinovirus. Although several epidemiological studies have generated substantial evidence of the association of biomass smoke and respiratory infections, the underlying mechanism is still unknown. Using an in vitro model, primary human lung fibroblasts were stimulated with biomass smoke extract (BME), specifically investigating hardwood and softwood types, and human rhinovirus-16 for 24 h. Production of pro-inflammatory mediators, such as IL-6 and IL-8, were measured via ELISA. Firstly, we found that hardwood and softwood smoke extract (1%) up-regulate IL-6 and IL-8 release (p &le; 0.05). In addition, human rhinovirus-16 further increased biomass smoke-induced IL-8 in fibroblasts, in comparison to the two stimulatory agents alone. We also investigated the effect of biomass smoke on viral susceptibility by measuring viral load, and found no significant changes between BME exposed and non-exposed infected fibroblasts. Activated signaling pathways for IL-6 and IL-8 production by BME stimulation were examined using signaling pathway inhibitors. p38 MAPK inhibitor SB239063 significantly attenuated IL-6 and IL-8 release the most (p &le; 0.05). This study demonstrated that biomass smoke can modulate rhinovirus-induced inflammation during infection, which can alter the severity of the disease. The mechanism by which biomass smoke exposure increases inflammation in the lungs can be targeted and inhibited via p38 MAP kinase pathway.

No MeSH data available.


Related in: MedlinePlus