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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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NLRP3 and caspase-1 are expressed and colocalized with CD68+ macrophages in acne lesionsThree-color immunofluorescence confocal images were obtained for NLRP3 (green), caspase-1 (red), and CD68 (blue) in a) acne lesions and b) normal skin. Original magnification 20× (scale bar represents 75 μm). The image is a representative data of at least three skin lesions obtained from skin lesions; c) The images were then super-imposed and double positive cells are shown in yellow (caspase-1+NLRP3), pink (caspase-1+CD68) and turquoise (NLRP3+CD68), original magnification 40× (scale bar represents 10 μm); and d) The overlay of NLRP3, caspase-1, CD68, is seen in increasing magnification, 40× and 63× (scale bar represents 2 μm) respectively, (left and middle); d) right panel represents staining of normal tissue, magnification 20×. Data is representative of experiments with tissue obtained from three independent donors.
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Figure 5: NLRP3 and caspase-1 are expressed and colocalized with CD68+ macrophages in acne lesionsThree-color immunofluorescence confocal images were obtained for NLRP3 (green), caspase-1 (red), and CD68 (blue) in a) acne lesions and b) normal skin. Original magnification 20× (scale bar represents 75 μm). The image is a representative data of at least three skin lesions obtained from skin lesions; c) The images were then super-imposed and double positive cells are shown in yellow (caspase-1+NLRP3), pink (caspase-1+CD68) and turquoise (NLRP3+CD68), original magnification 40× (scale bar represents 10 μm); and d) The overlay of NLRP3, caspase-1, CD68, is seen in increasing magnification, 40× and 63× (scale bar represents 2 μm) respectively, (left and middle); d) right panel represents staining of normal tissue, magnification 20×. Data is representative of experiments with tissue obtained from three independent donors.

Mentions: We examined acne lesions for in situ expression of NLRP3 and caspase-1 to correlate our in vitro findings and provide clinical relevance. Immunofluorescence labeling together with confocal laser microscopy using specific monoclonal antibodies revealed higher cellular expression of NLRP3 and active caspase-1 in the dermis surrounding the pilosebaceous follicles in acne lesions (Fig 5a, left and middle image) compared to normal skin control (Fig 5b, left and middle image). Additionally, a higher prevalence of CD68+ monocytes/macrophages in acne lesions (Fig 5a, right image) vs. normal skin control was noted (Fig 5b, right image). To confirm the cell lineage expressing NLRP3 and caspase-1 in acne lesions, we performed double immunofluorescence labeling utilizing monocyte/macrophage marker CD68. We first demonstrated that caspase-1 and NLRP3 co-localized (Fig. 5c, left image). In addition, both caspase-1 (Fig. 5c, middle) and NLRP3 (Fig. 5c, right) individually colocalized with CD68. These findings suggest that caspase-1 and NLRP3 are expressed in CD68+ monocytes/macrophages in acne lesions (Fig 5c). Triple immunofluorescence labeling showed that both NLRP3 and caspase-1 colocalized with the monocyte/macrophage marker CD68 (Fig. 5d, left and middle image). In contrast to acne lesions, staining of normal skin revealed few foci of NLRP3 and caspase-1 fluorescence within dermal macrophages (Fig 5d, right image).


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)

NLRP3 and caspase-1 are expressed and colocalized with CD68+ macrophages in acne lesionsThree-color immunofluorescence confocal images were obtained for NLRP3 (green), caspase-1 (red), and CD68 (blue) in a) acne lesions and b) normal skin. Original magnification 20× (scale bar represents 75 μm). The image is a representative data of at least three skin lesions obtained from skin lesions; c) The images were then super-imposed and double positive cells are shown in yellow (caspase-1+NLRP3), pink (caspase-1+CD68) and turquoise (NLRP3+CD68), original magnification 40× (scale bar represents 10 μm); and d) The overlay of NLRP3, caspase-1, CD68, is seen in increasing magnification, 40× and 63× (scale bar represents 2 μm) respectively, (left and middle); d) right panel represents staining of normal tissue, magnification 20×. Data is representative of experiments with tissue obtained from three independent donors.
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Figure 5: NLRP3 and caspase-1 are expressed and colocalized with CD68+ macrophages in acne lesionsThree-color immunofluorescence confocal images were obtained for NLRP3 (green), caspase-1 (red), and CD68 (blue) in a) acne lesions and b) normal skin. Original magnification 20× (scale bar represents 75 μm). The image is a representative data of at least three skin lesions obtained from skin lesions; c) The images were then super-imposed and double positive cells are shown in yellow (caspase-1+NLRP3), pink (caspase-1+CD68) and turquoise (NLRP3+CD68), original magnification 40× (scale bar represents 10 μm); and d) The overlay of NLRP3, caspase-1, CD68, is seen in increasing magnification, 40× and 63× (scale bar represents 2 μm) respectively, (left and middle); d) right panel represents staining of normal tissue, magnification 20×. Data is representative of experiments with tissue obtained from three independent donors.
Mentions: We examined acne lesions for in situ expression of NLRP3 and caspase-1 to correlate our in vitro findings and provide clinical relevance. Immunofluorescence labeling together with confocal laser microscopy using specific monoclonal antibodies revealed higher cellular expression of NLRP3 and active caspase-1 in the dermis surrounding the pilosebaceous follicles in acne lesions (Fig 5a, left and middle image) compared to normal skin control (Fig 5b, left and middle image). Additionally, a higher prevalence of CD68+ monocytes/macrophages in acne lesions (Fig 5a, right image) vs. normal skin control was noted (Fig 5b, right image). To confirm the cell lineage expressing NLRP3 and caspase-1 in acne lesions, we performed double immunofluorescence labeling utilizing monocyte/macrophage marker CD68. We first demonstrated that caspase-1 and NLRP3 co-localized (Fig. 5c, left image). In addition, both caspase-1 (Fig. 5c, middle) and NLRP3 (Fig. 5c, right) individually colocalized with CD68. These findings suggest that caspase-1 and NLRP3 are expressed in CD68+ monocytes/macrophages in acne lesions (Fig 5c). Triple immunofluorescence labeling showed that both NLRP3 and caspase-1 colocalized with the monocyte/macrophage marker CD68 (Fig. 5d, left and middle image). In contrast to acne lesions, staining of normal skin revealed few foci of NLRP3 and caspase-1 fluorescence within dermal macrophages (Fig 5d, right image).

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