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Propionibacterium acnes Induces IL-1β secretion via the NLRP3 inflammasome in human monocytes.

Qin M, Pirouz A, Kim MH, Krutzik SR, Garbán HJ, Kim J - J. Invest. Dermatol. (2013)

Bottom Line: Propionibacterium acnes induction of inflammatory responses is a major etiological factor contributing to the pathogenesis of acne vulgaris.Moreover, silencing of NLRP3, but not NLRP1, expression by small interfering RNA attenuated P. acnes-induced IL-1β secretion.The mechanism of P. acnes-induced NLRP3 activation and subsequent IL-1β secretion was found to involve potassium efflux.

View Article: PubMed Central - PubMed

Affiliation: Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA.

ABSTRACT
Propionibacterium acnes induction of inflammatory responses is a major etiological factor contributing to the pathogenesis of acne vulgaris. In particular, the IL-1 family of cytokines has a critical role in both initiation of acne lesions and in the inflammatory response in acne. In this study, we demonstrated that human monocytes respond to P. acnes and secrete mature IL-1β partially via the NLRP3-mediated pathway. When monocytes were stimulated with live P. acnes, caspase-1 and caspase-5 gene expression was upregulated; however, IL-1β secretion required only caspase-1 activity. P. acnes induced key inflammasome genes including NLRP1 and NLPR3. Moreover, silencing of NLRP3, but not NLRP1, expression by small interfering RNA attenuated P. acnes-induced IL-1β secretion. The mechanism of P. acnes-induced NLRP3 activation and subsequent IL-1β secretion was found to involve potassium efflux. Finally, in acne lesions, mature caspase-1 and NLRP3 were detected around the pilosebaceous follicles and colocalized with tissue macrophages. Taken together, our results indicate that P. acnes triggers a key inflammatory mediator, IL-1β, via NLRP3 and caspase-1 activation, suggesting a role for inflammasome-mediated inflammation in acne pathogenesis.

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P. acnes induction of IL-1β in human monocytesPrimary human monocytes from normal donors were stimulated in the presence or absence of various concentrations of live P. acnes (MOI of 0.1, 0.5 and 1.0) for 24 hours. a) IL-1β gene expression was assessed by qRT-PCR. Data represents 3 donors; b) Pro-IL-1β protein (31kD band) in the cell lysates was determined by western blot; and c) Mature IL-1β secretion into culture supernatant was assessed by ELISA. Monocytes were pretreated anti-TLR2, or isotype control mAbs 30 minutes prior to stimulation with P. acnes (MOI 0.5) and the induction of IL-1β at mRNA and supernatant protein levels was determined by qPCR (d) and ELISA (e) respectively. Data represent mean ± SD (n=3; *p ≤ 0.05, **p ≤ 0.01).
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Figure 1: P. acnes induction of IL-1β in human monocytesPrimary human monocytes from normal donors were stimulated in the presence or absence of various concentrations of live P. acnes (MOI of 0.1, 0.5 and 1.0) for 24 hours. a) IL-1β gene expression was assessed by qRT-PCR. Data represents 3 donors; b) Pro-IL-1β protein (31kD band) in the cell lysates was determined by western blot; and c) Mature IL-1β secretion into culture supernatant was assessed by ELISA. Monocytes were pretreated anti-TLR2, or isotype control mAbs 30 minutes prior to stimulation with P. acnes (MOI 0.5) and the induction of IL-1β at mRNA and supernatant protein levels was determined by qPCR (d) and ELISA (e) respectively. Data represent mean ± SD (n=3; *p ≤ 0.05, **p ≤ 0.01).

Mentions: Our previous studies showed that P. acnes induces the inflammatory cytokines IL-8 and IL-12 in human monocytes (Kim et al., 2002). In order to determine whether P. acnes induces IL-1β in primary human monocytes, we obtained monocytes from normal subjects and exposed them to live P. acnes at various MOIs (0.1, 0.5 and 1.0) for 24 hours and the expression of IL-1β mRNA was determined by qRT-PCR. P. acnes induced IL-1β gene expression by 100-200 fold in comparison to media control over a range of MOI (p<0.01, Fig. 1a). The induction of pro-IL-1p protein was determined by western blot analysis of cell lysates, confirming the upregulation of pro-IL-1β (31kD) when cells were stimulated with live P. acnes (Fig. 1b). In addition, secretion of mature IL-1β following stimulation with P. acnes was significantly induced (4,000-5,000 pg/ml) over a range of MOI (p<0.01) (Fig. 1c).


Propionibacterium acnes Induces IL-1β secretion via the NLRP3 inflammasome in human monocytes.

Qin M, Pirouz A, Kim MH, Krutzik SR, Garbán HJ, Kim J - J. Invest. Dermatol. (2013)

P. acnes induction of IL-1β in human monocytesPrimary human monocytes from normal donors were stimulated in the presence or absence of various concentrations of live P. acnes (MOI of 0.1, 0.5 and 1.0) for 24 hours. a) IL-1β gene expression was assessed by qRT-PCR. Data represents 3 donors; b) Pro-IL-1β protein (31kD band) in the cell lysates was determined by western blot; and c) Mature IL-1β secretion into culture supernatant was assessed by ELISA. Monocytes were pretreated anti-TLR2, or isotype control mAbs 30 minutes prior to stimulation with P. acnes (MOI 0.5) and the induction of IL-1β at mRNA and supernatant protein levels was determined by qPCR (d) and ELISA (e) respectively. Data represent mean ± SD (n=3; *p ≤ 0.05, **p ≤ 0.01).
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4116307&req=5

Figure 1: P. acnes induction of IL-1β in human monocytesPrimary human monocytes from normal donors were stimulated in the presence or absence of various concentrations of live P. acnes (MOI of 0.1, 0.5 and 1.0) for 24 hours. a) IL-1β gene expression was assessed by qRT-PCR. Data represents 3 donors; b) Pro-IL-1β protein (31kD band) in the cell lysates was determined by western blot; and c) Mature IL-1β secretion into culture supernatant was assessed by ELISA. Monocytes were pretreated anti-TLR2, or isotype control mAbs 30 minutes prior to stimulation with P. acnes (MOI 0.5) and the induction of IL-1β at mRNA and supernatant protein levels was determined by qPCR (d) and ELISA (e) respectively. Data represent mean ± SD (n=3; *p ≤ 0.05, **p ≤ 0.01).
Mentions: Our previous studies showed that P. acnes induces the inflammatory cytokines IL-8 and IL-12 in human monocytes (Kim et al., 2002). In order to determine whether P. acnes induces IL-1β in primary human monocytes, we obtained monocytes from normal subjects and exposed them to live P. acnes at various MOIs (0.1, 0.5 and 1.0) for 24 hours and the expression of IL-1β mRNA was determined by qRT-PCR. P. acnes induced IL-1β gene expression by 100-200 fold in comparison to media control over a range of MOI (p<0.01, Fig. 1a). The induction of pro-IL-1p protein was determined by western blot analysis of cell lysates, confirming the upregulation of pro-IL-1β (31kD) when cells were stimulated with live P. acnes (Fig. 1b). In addition, secretion of mature IL-1β following stimulation with P. acnes was significantly induced (4,000-5,000 pg/ml) over a range of MOI (p<0.01) (Fig. 1c).

Bottom Line: Propionibacterium acnes induction of inflammatory responses is a major etiological factor contributing to the pathogenesis of acne vulgaris.Moreover, silencing of NLRP3, but not NLRP1, expression by small interfering RNA attenuated P. acnes-induced IL-1β secretion.The mechanism of P. acnes-induced NLRP3 activation and subsequent IL-1β secretion was found to involve potassium efflux.

View Article: PubMed Central - PubMed

Affiliation: Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA.

ABSTRACT
Propionibacterium acnes induction of inflammatory responses is a major etiological factor contributing to the pathogenesis of acne vulgaris. In particular, the IL-1 family of cytokines has a critical role in both initiation of acne lesions and in the inflammatory response in acne. In this study, we demonstrated that human monocytes respond to P. acnes and secrete mature IL-1β partially via the NLRP3-mediated pathway. When monocytes were stimulated with live P. acnes, caspase-1 and caspase-5 gene expression was upregulated; however, IL-1β secretion required only caspase-1 activity. P. acnes induced key inflammasome genes including NLRP1 and NLPR3. Moreover, silencing of NLRP3, but not NLRP1, expression by small interfering RNA attenuated P. acnes-induced IL-1β secretion. The mechanism of P. acnes-induced NLRP3 activation and subsequent IL-1β secretion was found to involve potassium efflux. Finally, in acne lesions, mature caspase-1 and NLRP3 were detected around the pilosebaceous follicles and colocalized with tissue macrophages. Taken together, our results indicate that P. acnes triggers a key inflammatory mediator, IL-1β, via NLRP3 and caspase-1 activation, suggesting a role for inflammasome-mediated inflammation in acne pathogenesis.

Show MeSH
Related in: MedlinePlus