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Activation of vitamin D regulates response of human bronchial epithelial cells to Aspergillus fumigatus in an autocrine fashion.

Li P, Wu T, Su X, Shi Y - Mediators Inflamm. (2015)

Bottom Line: We found that A. fumigatus swollen conidia (SC) induced the expression of 1α-hydroxylase, the enzyme catalyzing the synthesis of active vitamin D, and vitamin D receptor (VDR) in 16HBE cells and led to increased local generation of active vitamin D.Furthermore, we identified β-glucan, the major A. fumigatus cell wall component, as the causative agent for upregulation of 1α-hydroxylase and VDR in 16HBE cells.Therefore, activation of vitamin D is inducible and provides a bidirectional regulation of the responses to A. fumigatus in 16HBE cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Respiratory and Critical Care Medicine, Jinling Hospital, Nanjing University School of Medicine, 305 East Zhongshan Road, Nanjing, Jiangsu 210002, China.

ABSTRACT
Aspergillus fumigatus (A. fumigatus) is one of the most common fungi to cause diseases in humans. Recent evidence has demonstrated that airway epithelial cells play an important role in combating A. fumigatus through inflammatory responses. Human airway epithelial cells have been proven to synthesize the active vitamin D, which plays a key role in regulating inflammation. The present study was conducted to investigate the impact of A. fumigatus infection on the activation of vitamin D and the role of vitamin D activation in A. fumigatus-elicited antifungal immunity in normal human airway epithelial cells. We found that A. fumigatus swollen conidia (SC) induced the expression of 1α-hydroxylase, the enzyme catalyzing the synthesis of active vitamin D, and vitamin D receptor (VDR) in 16HBE cells and led to increased local generation of active vitamin D. Locally activated vitamin D amplified SC-induced expression of antimicrobial peptides in 16HBE cells but attenuated SC-induced production of cytokines in an autocrine fashion. Furthermore, we identified β-glucan, the major A. fumigatus cell wall component, as the causative agent for upregulation of 1α-hydroxylase and VDR in 16HBE cells. Therefore, activation of vitamin D is inducible and provides a bidirectional regulation of the responses to A. fumigatus in 16HBE cells.

No MeSH data available.


Related in: MedlinePlus

Locally activated vitamin D synergistically increases the expression of LL-37 and HBD2 in 16HBE cells infected with A. fumigatus but attenuates A. fumigatus-induced production of chemokines and cytokines. (a)–(c) 16HBE cells were untreated (basal) or stimulated with resting conidia (RC) or swollen conidia (SC) (MOI = 1-2) for 24 h in the presence of either inactive (25D3; 10−7 M) or active vitamin D (1,25D3; 10−7 M). Locally activated vitamin D synergistically induces protein expression of LL-37 and β-defensin-2 (HBD2) to a similar extent as exogenous active vitamin D (a). The protein expression of LL-37 and β-defensin-2 (HBD2) was evaluated by Western blot analysis. The Western blots illustrated are from one representative experiment out of three and converted to densitometry units in respective graphs. (b)-(c) Locally activated vitamin D attenuates A. fumigatus-induced production of chemokines and cytokines in 16HBE cells to a similar extent as exogenous active vitamin D. TNF-α, IL-1β, IL-6, and IL-8 mRNA expression was measured using quantitative real-time PCR (b). The concentrations of TNF-α and IL-8 in culture supernatants of 16HBE cells were measured by ELISA (c). Values reflect mean fold change from control and SEM of three independent experiments. Student's t-test, ∗P < 0.05, ∗∗P < 0.01, and ∗∗∗P < 0.001, for comparison with baseline; #P < 0.05 and ##P < 0.01, for comparison with control.
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fig2: Locally activated vitamin D synergistically increases the expression of LL-37 and HBD2 in 16HBE cells infected with A. fumigatus but attenuates A. fumigatus-induced production of chemokines and cytokines. (a)–(c) 16HBE cells were untreated (basal) or stimulated with resting conidia (RC) or swollen conidia (SC) (MOI = 1-2) for 24 h in the presence of either inactive (25D3; 10−7 M) or active vitamin D (1,25D3; 10−7 M). Locally activated vitamin D synergistically induces protein expression of LL-37 and β-defensin-2 (HBD2) to a similar extent as exogenous active vitamin D (a). The protein expression of LL-37 and β-defensin-2 (HBD2) was evaluated by Western blot analysis. The Western blots illustrated are from one representative experiment out of three and converted to densitometry units in respective graphs. (b)-(c) Locally activated vitamin D attenuates A. fumigatus-induced production of chemokines and cytokines in 16HBE cells to a similar extent as exogenous active vitamin D. TNF-α, IL-1β, IL-6, and IL-8 mRNA expression was measured using quantitative real-time PCR (b). The concentrations of TNF-α and IL-8 in culture supernatants of 16HBE cells were measured by ELISA (c). Values reflect mean fold change from control and SEM of three independent experiments. Student's t-test, ∗P < 0.05, ∗∗P < 0.01, and ∗∗∗P < 0.001, for comparison with baseline; #P < 0.05 and ##P < 0.01, for comparison with control.

Mentions: Vitamin D plays an important role in innate immunity. The active form of vitamin D has been proven to prevent infections by bacteria (e.g., M. tuberculosis) or viruses by inducing the expression of the cathelicidin antimicrobial peptide and β-defensins [44, 45] and decreasing the inflammatory response to microbial infections [16, 46–49]. Exposure of respiratory epithelial cells to A. fumigatus increases the release of LL-37 and β-defensins and the expression of chemokines and cytokines that initiate an inflammatory reaction [3, 5–7]. Having established that 16HBE cells generate more active vitamin D and have upregulated VDR expression after stimulation with A. fumigatus, we hypothesized that when exposed to the inactive form of vitamin D, 16HBE cells stimulated with A. fumigatus would convert it to 1,25D3, which would alter the expression of inflammatory mediators and antimicrobial peptides induced by A. fumigatus in an autocrine fashion. To test this hypothesis, we initially treated 16HBE cells with 10−7 M of either the active or inactive form of vitamin D (1,25D3 or 25D3) and examined the protein expression of LL-37 and HBD2 in 16HBE cells stimulated with A. fumigatus for 24 h (Figure 2(a)). We found that both forms of vitamin D enhanced the basal expression of LL-37 and HBD2 in 16HBE cells to a similar extent. Regardless of treatment with either form of vitamin D, stimulation with RC did not change the expression of LL-37 or HBD2 in 16HBE cells. When stimulated with SC, the expression of LL-37 and HBD2 increased significantly. The presence of either 1,25D3 or 25D3 significantly augmented SC-induced expression of LL-37 and HBD2 to a similar extent in 16HBE cells.


Activation of vitamin D regulates response of human bronchial epithelial cells to Aspergillus fumigatus in an autocrine fashion.

Li P, Wu T, Su X, Shi Y - Mediators Inflamm. (2015)

Locally activated vitamin D synergistically increases the expression of LL-37 and HBD2 in 16HBE cells infected with A. fumigatus but attenuates A. fumigatus-induced production of chemokines and cytokines. (a)–(c) 16HBE cells were untreated (basal) or stimulated with resting conidia (RC) or swollen conidia (SC) (MOI = 1-2) for 24 h in the presence of either inactive (25D3; 10−7 M) or active vitamin D (1,25D3; 10−7 M). Locally activated vitamin D synergistically induces protein expression of LL-37 and β-defensin-2 (HBD2) to a similar extent as exogenous active vitamin D (a). The protein expression of LL-37 and β-defensin-2 (HBD2) was evaluated by Western blot analysis. The Western blots illustrated are from one representative experiment out of three and converted to densitometry units in respective graphs. (b)-(c) Locally activated vitamin D attenuates A. fumigatus-induced production of chemokines and cytokines in 16HBE cells to a similar extent as exogenous active vitamin D. TNF-α, IL-1β, IL-6, and IL-8 mRNA expression was measured using quantitative real-time PCR (b). The concentrations of TNF-α and IL-8 in culture supernatants of 16HBE cells were measured by ELISA (c). Values reflect mean fold change from control and SEM of three independent experiments. Student's t-test, ∗P < 0.05, ∗∗P < 0.01, and ∗∗∗P < 0.001, for comparison with baseline; #P < 0.05 and ##P < 0.01, for comparison with control.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4413954&req=5

fig2: Locally activated vitamin D synergistically increases the expression of LL-37 and HBD2 in 16HBE cells infected with A. fumigatus but attenuates A. fumigatus-induced production of chemokines and cytokines. (a)–(c) 16HBE cells were untreated (basal) or stimulated with resting conidia (RC) or swollen conidia (SC) (MOI = 1-2) for 24 h in the presence of either inactive (25D3; 10−7 M) or active vitamin D (1,25D3; 10−7 M). Locally activated vitamin D synergistically induces protein expression of LL-37 and β-defensin-2 (HBD2) to a similar extent as exogenous active vitamin D (a). The protein expression of LL-37 and β-defensin-2 (HBD2) was evaluated by Western blot analysis. The Western blots illustrated are from one representative experiment out of three and converted to densitometry units in respective graphs. (b)-(c) Locally activated vitamin D attenuates A. fumigatus-induced production of chemokines and cytokines in 16HBE cells to a similar extent as exogenous active vitamin D. TNF-α, IL-1β, IL-6, and IL-8 mRNA expression was measured using quantitative real-time PCR (b). The concentrations of TNF-α and IL-8 in culture supernatants of 16HBE cells were measured by ELISA (c). Values reflect mean fold change from control and SEM of three independent experiments. Student's t-test, ∗P < 0.05, ∗∗P < 0.01, and ∗∗∗P < 0.001, for comparison with baseline; #P < 0.05 and ##P < 0.01, for comparison with control.
Mentions: Vitamin D plays an important role in innate immunity. The active form of vitamin D has been proven to prevent infections by bacteria (e.g., M. tuberculosis) or viruses by inducing the expression of the cathelicidin antimicrobial peptide and β-defensins [44, 45] and decreasing the inflammatory response to microbial infections [16, 46–49]. Exposure of respiratory epithelial cells to A. fumigatus increases the release of LL-37 and β-defensins and the expression of chemokines and cytokines that initiate an inflammatory reaction [3, 5–7]. Having established that 16HBE cells generate more active vitamin D and have upregulated VDR expression after stimulation with A. fumigatus, we hypothesized that when exposed to the inactive form of vitamin D, 16HBE cells stimulated with A. fumigatus would convert it to 1,25D3, which would alter the expression of inflammatory mediators and antimicrobial peptides induced by A. fumigatus in an autocrine fashion. To test this hypothesis, we initially treated 16HBE cells with 10−7 M of either the active or inactive form of vitamin D (1,25D3 or 25D3) and examined the protein expression of LL-37 and HBD2 in 16HBE cells stimulated with A. fumigatus for 24 h (Figure 2(a)). We found that both forms of vitamin D enhanced the basal expression of LL-37 and HBD2 in 16HBE cells to a similar extent. Regardless of treatment with either form of vitamin D, stimulation with RC did not change the expression of LL-37 or HBD2 in 16HBE cells. When stimulated with SC, the expression of LL-37 and HBD2 increased significantly. The presence of either 1,25D3 or 25D3 significantly augmented SC-induced expression of LL-37 and HBD2 to a similar extent in 16HBE cells.

Bottom Line: We found that A. fumigatus swollen conidia (SC) induced the expression of 1α-hydroxylase, the enzyme catalyzing the synthesis of active vitamin D, and vitamin D receptor (VDR) in 16HBE cells and led to increased local generation of active vitamin D.Furthermore, we identified β-glucan, the major A. fumigatus cell wall component, as the causative agent for upregulation of 1α-hydroxylase and VDR in 16HBE cells.Therefore, activation of vitamin D is inducible and provides a bidirectional regulation of the responses to A. fumigatus in 16HBE cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Respiratory and Critical Care Medicine, Jinling Hospital, Nanjing University School of Medicine, 305 East Zhongshan Road, Nanjing, Jiangsu 210002, China.

ABSTRACT
Aspergillus fumigatus (A. fumigatus) is one of the most common fungi to cause diseases in humans. Recent evidence has demonstrated that airway epithelial cells play an important role in combating A. fumigatus through inflammatory responses. Human airway epithelial cells have been proven to synthesize the active vitamin D, which plays a key role in regulating inflammation. The present study was conducted to investigate the impact of A. fumigatus infection on the activation of vitamin D and the role of vitamin D activation in A. fumigatus-elicited antifungal immunity in normal human airway epithelial cells. We found that A. fumigatus swollen conidia (SC) induced the expression of 1α-hydroxylase, the enzyme catalyzing the synthesis of active vitamin D, and vitamin D receptor (VDR) in 16HBE cells and led to increased local generation of active vitamin D. Locally activated vitamin D amplified SC-induced expression of antimicrobial peptides in 16HBE cells but attenuated SC-induced production of cytokines in an autocrine fashion. Furthermore, we identified β-glucan, the major A. fumigatus cell wall component, as the causative agent for upregulation of 1α-hydroxylase and VDR in 16HBE cells. Therefore, activation of vitamin D is inducible and provides a bidirectional regulation of the responses to A. fumigatus in 16HBE cells.

No MeSH data available.


Related in: MedlinePlus