Keratinocyte proliferation is important for skin wound healing. The wound healing process includes blood clotting around the wound, removal of dead cells and pathogens through inflammation, and then re-epithelialization through proliferation and maturation. Proliferation assay was performed on acid natural compounds to identify candidates for natural-derived components of skin injury treatment. We found that gentisic acid promoted high cell proliferation activity compared with other compounds. Gentisic acid improved HaCaT cell proliferation by over 20% in MTT assay. Gentisic acid also had higher healing activity in an in vitro wound healing assay than allantoin as a positive control. Furthermore, we have identified how the treatment of gentisic acid can increase proliferation in the cell. Western blot analysis of proteins in the mitogen-activated protein (MAP) kinase signaling pathway showed that ERK1/2 phosphorylation was increased by gentisic acid treatment. Thus, our study indicates that gentisic acid promotes the proliferation of keratinocyte by phosphorylation of ERK1/2.

Acne is an inflammatory skin disorder; although some anti-inflammatory medicines for treating acne are available in a market, they have considerable side effects; therefore, new treatment options are needed. In the present study, among the 16 aqueous extracts of plants collected from Jeju Island in Korea which are used to test anti-inflammatory activity, B. davidii showed the strong decline of the proinflammatory cytokine expression against the inflammatory process caused by C. acnes in Human HaCaT keratinocyte cells. B. davidii downregulated the expression of 57% of COX-2, 41% of iNOS, and proinflammatory cytokines 29% of TNF-α, 32% of IL-1β, 21% of IL-6, and 35% of IL-8. Furthermore, B. davidii inhibited NF-κB and MAPK signaling cascades in keratinocytes that activated by toll-like receptor 2 (TLR-2) in response to C. acnes. Given those results, B. davidii is a potential agent to reduce the proinflammatory cytokine expression against C. acnes-induced inflammation and might provide an alternative to the current medications.

Cell migration and proliferation are important for proper wound healing after skin injury. Recent studies have shown that compounds from plants could promote cell migration and proliferation. Tracheloside, which is a plant lignan, has been found to promote the growth of HaCaT cells over 40% compared to other compounds tested based on a cell proliferation assay. Anin vitroscratch assay confirmed the healing activity of tracheloside (more than 2‐fold increased healing activity after 24 hours of treatment compared with the control) and revealed that this activity is better than that of allantoin (1.2‐fold increased after 24 hours of treatment compared with the control), a positive control. With western blot results, wound healing with tracheloside occurred through the phosphorylation of ERK1/2. Therefore, tracheloside is a good candidate to promote wound healing and could be developed as a therapeutic agent for wound treatment or used as a leading compound with higher activity.

Introduction. Rhein (4, 5-dihydroxyanthraquinone-2-carboxylic acid) has various properties, including anti-inflammatory, antioxidant and anticancer activities. However, the mechanism underlying the role of rhein in antimicrobial activity remains largely unknown. Aim. This study aims to identify potential natural compounds of rhein that are capable of inhibiting Cutibacterium acnes and elucidate the effects of rhein on NADH dehydrogenase-2 activity in C. acnes. Methodology. The anti-C. acnes activity of compounds was analysed using minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), the paper disc diffusion test and the checkerboard dilution test. To check whether rhein was inhibitory, putative type II NADH dehydrogenase (NDH-2) of C. acnes was analysed, cloned and expressed in Escherichia coli, and then NDH-2 purification was assessed with Ni-NTA before rhein inhibition of NADH dehydrogenase-2 activity was checked with ferricyanide [K3Fe(CN)(6)] as a substrate. Results. The results showed that the MIC of rhein against C. acnes was 6.25 mu g ml(-1), while the MBC was 12.5 mu g ml(-1), and there was a 38 mm inhibition zone in the paper disc diffusion test. Rhein showed an additive two- to fourfold reduction of the MIC value with four antibiotics on the checkerboard dilution test. The purified NADH dehydrogenase gene product showed a size of approximately 51 kDa and had a V-max of 23 mu mol and a K-m of 280 mu m. The inhibitory effect of rhein against NADH dehydrogenase-2 activity was non-competitive with ferricyanide [K3Fe(CN)(6)] with a K-i value of 3.5-4.5 mu m. Conclusion. This study provided evidence of the inhibitory effects of rhein on the growth of C. acnes by blocking of NADH dehydrogenase-2 activity. This mechanism of inhibitory activity in the reduction of ROS formation and ATP productivity should be further tested in C. acnes and the question of whether rhein inhibits the natural growth of C. acnes should be investigated.

Glutamate is an important neurotransmitter in the central nervous system; however, at high concentrations, it causes excitotoxicity and many neurological disorders. Excitotoxicity induces cell death by apoptosis. Thus, factors that can inhibit the apoptotic pathways are a target of drug development for the treatment and prevention of neurodegenerative diseases. Herein, the antioxidative and neuroprotective effects of myristargenol A were examined in glutamate-induced mouse hippocampal neuronal HT22 cells. When the HT22 cells were stressed with glutamate, cell viability decreased to 44.4 ± 5.6% when compared with the case of the control cells (100 ± 4.8%); however, when these cells were treated with myristargenol A (10 μM), the cell viability was increased by 113.6 ± 2.3%. The protective effect of myristargenol A against the apoptosis of glutamate-induced HT22 cells was also confirmed using FITC-annexin V/propidium iodide double staining. In addition, myristargenol A protected the mitochondrial membrane potential (ΔΨ_m). Subsequently, the expression levels of proteins in the caspase pathway related with the induction of apoptosis were decreased. Moreover, the expression levels of mitochondrial-related proteins, such as Bcl-2 and Bax, were examined, and it was found that the expression ratio of Bax/Bcl-2 decreased. In addition, myristargenol A inhibited the activity of mitogen-activated protein kinases, including p38 and c-Jun N-terminal kinase, for an oxidative stress protection effect but increased the activity of the extracellular signal-regulated kinases 1 and 2 for cell proliferation. These results reveal that myristargenol A possesses a neuroprotective effect against the neuronal cell damage caused by glutamate.