Noriko Akimoto

Involvement of Propionibacterium acnes in the Augmentation of Lipogenesis in Hamster Sebaceous Glands In Vivo and In Vitro

Propionibacterium acnes is considered to be involved in the aggravation of acne vulgaris, but it remains unclear whether P. acnes directly influences lipogenesis in sebaceous glands. In this study, we showed that a culture medium of P. acnes (acnes-CM) and formalin-killed P. acnes (F-acnes) prepared from P. acnes strains, JCM6473 and JCM6425, intracellularly augmented lipid droplet formation and triacylglycerol (TG) synthesis in undifferentiated and insulin-differentiated hamster sebocytes. Acnes-CM and F-acnes prepared from four clinical P. acnes strains elicited the same lipogenesis augmentation. The augmented TG production resulted from an increase in the diacylglycerol acyltransferase activity. Topical application of acnes-CM to the skin of hamster auricles every day for 4 weeks revealed that sebum accumulation was augmented in sebaceous glands and ducts. Furthermore, both acnes-CM and F-acnes increased the production of 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), a cytochrome P450 (CYP)-linked sebaceous lipogenic factor, in differentiated sebocytes. A CYP inhibitor, SKF-525A, decreased the acnes-CM- and F-acnes-augmented production of TG and 15d-PGJ(2). Thus, to our knowledge these results provide previously unreported evidence that P. acnes directly participates in the augmentation of sebaceous lipogenesis through a proposed mechanism in which an increase of 15d-PGJ(2) production through the CYP pathway is closely associated with the enhancement of TG production.

Cell proliferation and lipid formation in hamster sebaceous gland cells.

Background: The development of sebocytes and lipogenesis are known to be dependent on androgens. However, it is not fully understood whether growth factors are involved in the regulation of cell proliferation and lipid formation in sebaceous glands. Objective: This study was designed to evaluate the effect of growth factors such as epidermal growth factor (EGF), transforming growth factor α (TGF-α), basic fibroblast growth factor (bFGF) and keratinocyte growth factor (KGF) on cell proliferation and lipogenesis in cultured hamster sebocytes. Methods: Cell proliferation and intracellular lipid accumulation in these hamster sebocytes treated with growth factors were examined. Results: EGF, TGF-α and bFGF augmented the proliferation of hamster sebocytes for 8 days in a time- and dose-dependent manner. However, KGF had no effect on their proliferation. Moreover, the accumulation of intracellular lipids consisting mainly of triglycerides was suppressed in EGF-, TGF-α-, bFGF- and KGF-treated hamster sebocytes. Conclusion: EGF, TGF-α and bFGF, but not KGF, have mitogenic activity on hamster sebocytes, and all these growth factors act as antilipogenic factors. Moreover, it is likely that the formation of intracellular lipid droplets is independent of cell proliferation in hamster sebocytes.

Adiponectin resides in mouse skin and upregulates hyaluronan synthesis in dermal fibroblasts

Adipose tissue is a hormonally active tissue that produces adipokines that influence the activity of other tissues. Adiponectin is an adipocyte-specific adipokine involved in systemic metabolism. We detected the expression of adiponectin receptors (AdipoR1 and AdipoR2) mRNA in cultured dermal fibroblasts. The full-length adiponectin (fAd), but not the globular adiponectin (gAd), increased hyaluronan (HA) production and upregulated HA synthase (HAS) 2 mRNA expression. AdipoR1 and AdipoR2 mRNAs were also expressed in keratinocytes, though neither fAd nor gAd had any effect on HA synthesis. In mouse skin, we found that adiponectin was present and decreased markedly with aging. The age-dependent pattern of adiponectin decrease in skin, correlated well with that of HA in skin. Our experiments were also the first to identify adiponectin production in cultured mouse sebocytes, a finding that suggests that skin adiponectin may derive not only from plasma and/or subcutaneous adipose tissue, but also from the sebaceous gland. These results indicated that adiponectin plays an important role in the HA metabolism of skin.

Augmentation of sebaceous lipogenesis by an ethanol extract of Grifola frondosa (Maitake mushroom) in hamsters in vivo and in vitro

Abstract:  Grifola frondosa (Maitake mushroom) is an edible and medicinal mushroom with versatile effects such as antitumor and immunomodulating actions. Here, we demonstrated that an ethanol extract of G. frondosa fruiting body (Maitake extract) augmented intracellular lipid droplet formation and the production of triacylglycerols (TG), a major component of sebum, along with the activation of diacylglycerol acyltransferase, a rate‐limiting enzyme of TG synthesis in cultured hamster sebocytes. The topical treatment of Maitake extract on the skin of hamster auricles augmented sebum accumulation in sebaceous glands and ducts. However, in comparison with the Maitake extract, another ethanol extract prepared from Agaricus blazei Murill showed less activity in sebaceous lipogenesis in hamsters in vivo and in vitro. These results provide novel evidence that Maitake extract augments sebaceous lipogenesis in hamsters in vivo and in vitro. Thus, Maitake extract is likely to be a unique agent leading to the remission of dry skin.

A novel functional site of extracellular matrix metalloproteinase inducer (EMMPRIN) that limits the migration of human uterine cervical carcinoma cells

EMMPRIN (extracellular matrix metalloproteinase inducer)/CD147, a membrane-bound glycoprotein with two extracellular loop domains (termed loops I and II), progresses tumor invasion and metastasis by increasing the production of matrix metalloproteinase (MMP) in peritumoral stoma cells. EMMPRIN has also been associated with the control of migration activity in some tumor cells, but little is known about how EMMPRIN regulates tumor cell migration. In the present study, EMMPRIN siRNA suppressed the gene expression and production of EMMPRIN in human uterine cervical carcinoma SKG-II cells. An in vitro scratch wound assay showed enhancement of migration of EMMPRIN-knockdown SKG-II cells. In addition, the SKG-II cell migration was augmented by adding an E. coli-expressed human EMMPRIN mutant with two extracellular loop domains (eEMP-I/II), which bound to the cell surface of SKG-II cells. However, eEMP-I/II suppressed the native EMMPRIN-mediated augmentation of proMMP-1/procollagenase-1 production in a co-culture of the SKG-II cells and human uterine cervical fibroblasts, indicating that the augmentation of SKG-II cell migration resulted from the interference of native EMMPRIN functions by eEMP-I/II on the cell surface. Furthermore, a systematic peptide screening method using nine synthetic EMMPRIN peptides coding the loop I and II domains (termed EM1-9) revealed that EM9 (170HIENLNMEADPGQYR184) facilitated SKG-II cell migration. Moreover, SKG-II cell migration was enhanced by administration of an antibody against EM9, but not EM1 which is a crucial site for the MMP inducible activity of EMMPRIN. Therefore, these results provide novel evidence that EMMPRIN on the cell surface limits the cell migration of human uterine cervical carcinoma cells through 170HIENLNMEADPGQYR184 in the loop II domain. Finally, these results should provide an increased understanding of the functions of EMMPRIN in malignant cervical carcinoma cells, and could contribute to the development of clinical strategies for cervical cancer therapy.

Adapalene suppresses sebum accumulation via the inhibition of triacylglycerol biosynthesis and perilipin expression in differentiated hamster sebocytes in vitro

BACKGROUND Acne is a chronic inflammatory disease in sebaceous glands and pilosebaceous units where excess sebum production and follicular hyperkeratinization are observed. Adapalene, which exerts comedolytic and anti-inflammatory effects, is used for the topical treatment of mild to moderate acne. OBJECTIVE We examined the effect of adapalene on sebum production and accumulation in sebaceous gland cells (sebocytes). METHODS The regulation of sebum production was examined by oil red O and nile red staining and the measurement of triacylglycerols (TGs) in differentiated hamster sebocytes. The gene expression and production of diacylglycerol acyltransferase-1 (DGAT-1) and perilipin 1 (PLIN1) were analyzed using real-time PCR and Western blotting, respectively. RESULTS Adapalene suppressed sebum accumulation as lipid droplets in spontaneously and insulin-differentiated hamster sebocytes. The TG production, and the gene expression and production of DGAT-1, a rate-limiting enzyme of TG biosynthesis, were dose-dependently inhibited by adapalene in insulin-, 5α-dihydrotestosterone- or a peroxisome proliferator activating receptor γ agonist, troglitazone-differentiated hamster sebocytes. In addition, the inhibition of TG production by adapalene interfered with antagonists against nuclear retinoic acid and retinoid X receptors (CD2665 and UVI3006, respectively) in the differentiated sebocytes. Furthermore, the production of PLIN1, a lipid storage droplet protein, was transcriptionally inhibited by adapalene in the differentiated sebocytes. CONCLUSIONS These results suggest that adapalene exerts an inhibitory action for sebum accumulation due to the suppression of TG and PLIN1 production in differentiated hamster sebocytes. Furthermore, these findings may contribute to a novel understanding of the molecular mechanisms of adapalene for acne treatment and prevention.

Induction of inflammatory reactions by lipopolysaccharide in hamster sebaceous glands and pilosebaceous units in vivo and in vitro

Abstract:  Lipopolysaccharide (LPS) from Gram‐negative bacteria has been reported to exert inflammatory reactions in epidermis, dermis, and sebaceous glands. Here, we demonstrated that the intradermal administration of Escherichia coli‐derived LPS, three times a week for 4 weeks, to hamster auricle skin did not influence sebaceous morphology or sebum accumulation in sebaceous glands but in fact induced epidermal thickness. In addition, the administration of LPS, once a day for 2 days, augmented the production of cyclooxygenase 2 (COX‐2) in sebaceous glands. Furthermore, LPS increased the production of prostaglandin F2α (PGF2α) in hamster sebocytes. Moreover, the production of progelatinase A/promatrix metalloproteinase 2 (proMMP‐2) was transcriptionally augmented by LPS and PGF2α in hamster sebocytes. Therefore, these results suggest that LPS directly increases inflammation by augmenting COX‐2, PGF2α, and the PGF2α‐mediated proMMP‐2 production in sebaceous glands as well as epidermal inflammatory events in skin disorders including acne and folliculitis.

Triptolide suppresses ultraviolet B‑enhanced sebum production by inhibiting the biosynthesis of triacylglycerol in hamster sebaceous glands in vivo and in vitro

Ultraviolet B (UVB) irradiation causes alterations in cutaneous barrier function, including excessive production of sebum in sebaceous glands, which is associated with the aggravation of acne. This study aimed to evaluate the inhibitory effects of triptolide, a diterpenoid triepoxide from Tripterygium wilfordii Hook F, on sebocytic lipogenesis in UVB-irradiated hamster skin in vivo and in vitro. Topical application of triptolide decreased the UVB-enhanced sebum accumulation in the sebaceous glands of hamster skin. The level of triacylglycerol (TG), a major sebum component, on the skin surface was reduced by triptolide treatment in UVB-irradiated hamsters, whereas there was no change in that of free-fatty acids and cholesterol, which are minor sebum components. UVB irradiation significantly enhanced TG production (P<0.01 in extracellular lipids, P<0.05 in intracellular lipids), and the activity of acyl coenzyme A/diacylglycerol acyltransferase (DGAT), a rate-limiting enzyme of TG synthesis, in differentiated hamster sebocytes (P<0.05 at 6 h and UVB of 0.62 kJ/m2, P<0.001 at 24 h and UVB 0.37 or 0.62 kJ/m2). Furthermore, triptolide significantly inhibited UVB-enhanced TG production (P<0.05 at 28 nM and P<0.01 at 56 and 112 nM triptolide) and DGAT activity (P<0.01 at 28 nM and P<0.001 at 56 and 112 nM triptolide) in differentiated hamster sebocytes. These results provide novel evidence that triptolide decreases UVB-enhanced sebum production by inhibiting DGAT-dependent TG biosynthesis in differentiated hamster sebocytes. These findings may be applicable to the prevention of acne aggravation.

Differentiated hamster sebocytes exhibit apoptosis-resistant phenotype by the augmentation of intracellular calcium level in vitro

Sebaceous glands play important roles in the maintenance of the skin barrier function by secreting sebum onto the skin surface. In our study, we demonstrated that differentiated hamster sebocytes (DHS) exhibited apoptosis resistance and the loss of Ca2+ influx against a calcium ionophore, A23187 treatment, which induced both apoptosis and Ca2+ influx in undifferentiated hamster sebocytes (unDHS). The Fluo‐3‐related signal of intracellular Ca2+ in the DHS was higher than that in unDHS and was sustained even though there was a depletion of Ca2+ from the culture medium. Furthermore, the intracellular Ca2+ chelator, BAPTA‐AM, was found to decrease the Ca2+ signal in the DHS, which induced apoptosis. Thus, these results provide novel evidence that the cell differentiation‐dependent increase in store‐operated Ca2+ release is associated with apoptosis resistance in the DHS. Moreover, these findings should accelerate the understanding of the mechanisms of sebogenesis and/or sebum production and secretion under physiological conditions.

Involvement of adenosine triphosphate-binding cassette subfamily B member 1 in the augmentation of triacylglycerol excretion by Propionibacterium acnes in differentiated hamster sebocytes

An onset of acne, a common inflammatory skin disease, is associated with excess sebum production and secretion in sebaceous glands. Because Propionibacterium acnes has been reported to augment intracellular sebum accumulation in sebaceous glands in hamsters, it remains unclear whether P. acnes influences sebum secretion from differentiated sebocytes. Both P. acnes culture media (Acnes73‐CM) and formalin‐killed P. acnes (F‐Acnes73) dose‐dependently increased the extracellular levels of triacylglycerol (TG), a major sebum component, and Rhodamine 123, a substrate of adenosine triphosphate‐binding cassette (ABC) transporter, from differentiated hamster sebocytes (DHS). In addition, the gene expression of the ABC subfamily B member 1 (ABCB1) was dose‐dependently augmented by adding Acnes73‐CM and F‐Acnes73 into DHS. Furthermore, the F‐Acnes73‐induced increase of TG excretion was suppressed by PSC833, a selective ABCB1 inhibitor. On the other hand, peptidoglycan (PGN), which is a Toll‐like receptor 2 (TLR2) ligand in P. acnes, increased extracellular TG levels, transporter activity and ABCB1 mRNA expression in DHS. The PGN‐augmented TG excretion was suppressed by PSC833. Thus, these results provide novel evidence that P. acnes facilitates sebum secretion due to the activation of ABCB1 concomitantly with the increased ABCB1 expression, which may result from the activation of the TLR2 pathway in DHS. Therefore, the ABCB1 inhibitor is likely to become a candidate as a possible therapeutic for the treatment of acne.