Propionibacterium acnes-induced IL-8 production may be mediated by NF-kappaB activation in human monocytes

Propionibacterium acnes and lipopolysaccharide induce the expression of antimicrobial peptides and proinflammatory cytokines/chemokines in human sebocytes

Acne is a common skin disorder of the pilosebaceous unit. In addition to genetic, hormonal and environmental factors, abnormal colonization by Propionibacterium acnes has been implicated in the occurrence of acne via the induction of inflammatory mediators. To gain more insight into the role that sebocytes play in the innate immune response of the skin, particularly in acne, we compared the antimicrobial peptide and proinflammatory cytokine/chemokine expression at mRNA and protein levels, as well as the viability and differentiation of SZ95 sebocytes in response to co-culture with representative isolates of P. acnes type IA and type IB as well as Escherichia coli-derived lipopolysaccharide (LPS). We found that, in vitro, P. acnes type IA and IB isolates and LPS induced human beta-defensin-2 and proinflammatory cytokine/chemokine expression, and influenced sebocyte viability and differentiation. Our results provide evidence that sebocytes are capable of producing proinflammatory cytokines/chemokines and antimicrobial peptides, which may have a role in acne pathogenesis. Furthermore, since P. acnes types IA and IB differentially affect both the differentiation and viability of sebocytes, our data demonstrate that different strains of P. acnes vary in their capacity to stimulate an inflammatory response within the pilosebaceous follicle.

Neutrophil elastase induces IL-8 gene transcription and protein release through p38/NF-{kappa}B activation via EGFR transactivation in a lung epithelial cell line

In this study, we investigated the regulation and mechanism of IL-8 expression by A549 human lung carcinoma cells treated with neutrophil elastase (NE). NE-treated cells exhibited significantly higher IL-8 protein levels in culture media compared with cells treated with vehicle alone. Blocking of gene transcription with actinomycin D suggested that NE stimulated IL-8 synthesis via increased mRNA expression, which was verified by real-time RT-PCR. NE activated the IL-8 promoter but did not alter the stability of its mRNA, confirming that the protease induced IL-8 synthesis through increased gene transcription. The results from the use of chemical inhibitors and mutant gene constructs against various signal transduction components seem to suggest the linear signaling pathway involving the activation of PKC-delta --> dual oxidase 1 --> reactive oxygen species --> TNF-alpha-converting enzyme --> EGF receptor --> p38 --> NF-kappaB for NE-activated IL-8 gene expression. A NF-kappaB potential binding site, located between nucleotides -82 and -69 of the IL-8 promoter, was identified as necessary for NE-induced IL-8 transcription. We conclude that NE increases IL-8 transcription through p38/NF-kappaB activation via EGFR transactivation.

Induction of a chemoattractive proinflammatory cytokine response after stimulation of keratinocytes with Propionibacterium acnes and coproporphyrin III

BACKGROUND

The inflammation in acne vulgaris is widely thought to be induced by an immunological reaction, but the role of Propionibacterium acnes is unclear.

OBJECTIVES

To examine the local host response mechanism of a keratinocyte cell line 3 h and 6 h after stimulation with viable and heat-killed P. acnes.

METHODS

The quantitative expression of cytokines was measured at the mRNA level by real-time reverse transcription-polymerase chain reaction.

RESULTS

The coincubation of a keratinocyte cell line with viable, but not heat-killed, P. acnes modulated an adequate cytokine response for interleukin (IL)-1beta, granulocyte/macrophage colony-stimulating factor and IL-8. High-performance liquid chromatographic analysis of the in vivo porphyrin pattern secreted by P. acnes revealed a predominance of coproporphyrin III in acne lesions. This same porphyrin fraction also modestly induced IL-8 expression by keratinocytes.

CONCLUSIONS

This cytokine pattern may favour a chemotactic response and implicates P. acnes and coproporphyrin III in the recruitment of inflammatory cells to the site of infection and in the development of acne lesions.

Mechanism of Thymus- and Activation-Regulated Chemokine (TARC)/CCL17 Production and its Modulation by Roxithromycin

Stimulation with tumor necrosis factor (TNF)alpha and interferon (IFN)gamma synergistically induced thymus- and activation-regulated chemokine (TARC)/CCL17 production from HaCaT keratinocytes (KC). Inhibitors for nuclear factor kappa B (NFkappaB), parthenolide, and Bay 11-7085, and an inhibitor of p38, SB202190, inhibited TNFalpha- and IFNgamma-induced production of CCL17 by HaCaT KC. Surprisingly, an inhibitor of epidermal growth factor receptor tyrosine kinase, PD153035, enhanced the production of CCL17 in HaCaT KC. Roxithromycin (RXM), a 14-membered ring macrolide, suppressed CCL17 production by HaCaT KC induced by IFNgamma and TNFalpha. RXM partially suppressed p38 phosphorylation and NFkappaB-driven luciferase activity induced by TNFalpha and IFNgamma. Degradation of inhibitor of nuclear factor kappa B (IkappaB) alpha upon stimulation with IFNgamma and TNFalpha was not affected by the addition of RXM. Through elucidating the mechanism of CCL17 production, our study indicates that RXM suppresses the production through the inhibition of p38 and NFkappaB, independent of the inhibition of IkappaB degradation.

The Role of Toll-Like Receptors in the Pathophysiology of Acne

Acne vulgaris is a common cutaneous disorder of the pilosebaceous follicle, affecting more than 45 million people in the United States alone. The pathogenesis of acne is multifactorial, involving abnormal hyperkeratinization, increased sebum production, hormones, cutaneous microbes, and immunological mechanisms. Many of the immunological processes that contribute to the formation of acne lesions take place at the very site of disease, the skin. Skin is an important component of the innate immune system, providing both physical barriers and rapid cellular responses by keratinocytes, Langerhans cells, and other infiltrating inflammatory cells. In this review, we discuss the ability of the innate immune system to use Toll-like receptors (TLRs) to recognize microbial patterns and initiate immune responses in cutaneous disorders. Because TLRs are vital players in infectious and inflammatory diseases, they are potential therapeutic targets. Indeed, the ability of TLRs to combat disease already has been harnessed through the development of drugs that act as TLR agonists. A better understanding of TLRs will allow for the development of new therapeutic options for cutaneous inflammatory diseases such as acne.

Acne: inflammation

The inflammatory stage of acne vulgaris is usually of greatest concern to the patient. A number of morphologically different inflammatory lesions may form that can be painful and unsightly. In 30% of patients, such lesions lead to scarring(1). Inflammatory acne and acne scarring can have significant psychological effects on the patient, including depression, anxiety, and poor self-image(2). Although inflammatory acne has been well characterized clinically, the mechanisms by which inflammatory lesions arise are still poorly understood. The human skin commensal bacterium, Propionibacterium acnes, has long been associated with inflammatory acne. This organism has been implicated over and above all of the other cutaneous microflora in contributing to the inflammatory response characteristic of acne. However, its precise role in the disease and its interaction with the human immune system remain to be elucidated.

Roxithromycin Suppresses Mucin Gene Expression in Epithelial Cells

Macrolide antibiotics are believed to inhibit mucus secretion but the mechanism of action is unclear. This study was designed to investigate an effect of roxithromycin on MUC2 gene expression in cultured intestinal epithelial cells (HM3-MUC2 cells). A reporter gene assay was used for analysis. Roxithromycin suppressed MUC2 gene transcriptional activity in a dose-dependent manner in HM3-MUC2 cells. Phorbol 12-myristate 13-acetate (PMA), lipoteichoic acid (LTA), lipopolysaccharide (LPS) and leukotriene D4 (LTD4) significantly increased MUC2 luciferase activities in the following order: PMA > LTA > LTD4 > LPS. Roxithromycin also decreased MUC2 gene transcriptional activity induced by PMA in a dose-dependent manner. NF-kappaB activation, but not AP-1 activation, was significantly suppressed by roxithromycin in HM3-MUC2 cells. A suppression of NF-kappaB activation was also observed in NCI-H292 cells. These results suggest that roxithromycin suppresses MUC2 gene expression in epithelial cells and that this suppression is probably via inhibition of NF-kappaB activation.

Update and future of systemic acne treatment

Systemic treatment is required in patients with moderate-to-severe acne, especially when acne scars start to occur. Antibiotics with anti-inflammatory properties, such as tetracyclines (oxytetracycline, tetracycline chloride, doxycycline, minocycline and limecycline) and macrolide antibiotics (erythromycin and azithromycin) are the agents of choice for papulopustular acne, even though the emerging resistant bacterial strains are minimizing their effect, especially regarding erythromycin. Systemic antibiotics should be administered during a period of 8-12 weeks. In severe papulopustular and in nodulocystic/conglobate acne, oral isotretinoin is the treatment of choice. Hormonal treatment represents an alternative regimen in female acne, whereas it is mandatory in resistant, severe pubertal or post-adolescent forms of the disease. Compounds with anti-androgenic properties include estrogens combined with progestins, such as ethinyl estradiol with cyproterone acetate, chlormadinone acetate, desogestrel, drospirenone, levonogestrel, norethindrone acetate, norgestimate, and other anti-androgens directly blocking the androgen receptor (flutamide) or inhibiting androgen activity at various levels, corticosteroids, spironolactone, cimetidine, and ketoconazole. After 3 months of treatment control of seborrhea and acne can be obtained. Low-dose corticosteroids (prednisone, prednisolone, or dexamethasone) are indicated in patients with adrenal hyperandrogenism or acne fulminans. New developments and future trends represent low-dose long-term isotretinoin regimens, new isotretinoin formulations (micronized isotretinoin), isotretinoin metabolites, combination treatments to reduce toxicity, insulin-sensitizing agents, 5alpha-reductase type 1 inhibitors, antisense oligonucleotide molecules, and, especially, new anti-inflammatory agents, such as lipoxygenase inhibitors.

Update on pathogenesis and treatment of acne

Acne vulgaris is a common cutaneous disorder of the pilosebaceous follicle. More than 45 million people are affected with acne vulgaris. In addition, 80% of people in the United States report that they suffered from acne at one point in life. It is estimated that US consumers spend $1.2 billion each year for the treatment of acne. Typically, lesions are pleomorphic and range from open and closed comedones to inflammatory papules, pustules, cysts, and nodules, and scarring may result. The disease is important, with a significant effect on patients' self-esteem. The pathogenesis is only partially understood and is multifactorial. Successful management of acne requires an understanding of the pathophysiology of disease. The first half of this review discusses new discoveries in the pathogenesis of acne, and the second half introduces new and time-honored therapies.

The role of innate immunity in the pathogenesis of acne

Acne is a multifactorial disease of the pilosebaceous follicle. The most significant pathogenetic factors of acne are: abnormal ductal keratinization, increased sebum secretion, abnormalities of the microbial flora and inflammation. The pilosebaceous unit is an immunocompetent organ. Keratinocytes and sebocytes may act as immune cells capable of pathogen recognition and abnormal lipid presentation, and they might have an important role in initiating and perpetuating the activation of both innate and adaptive immune responses. The elements of the skin immune system are involved in the development of both noninflammatory and inflammatory acne lesions.