Evaluation of skin phototoxicity of transdermally administered pharmaceuticals in Sprague-Dawley rats / 한국실험동물학회지

Some drugs cause phototoxicity in humans when exposed to light, thus there is a need for an in vivo phototoxicity test to evaluate them. However, an in vivo phototoxicity test method to evaluate this has not been established. This study aimed to establish an in vivo phototoxicity test method for transdermally administered drugs. For this, we evaluated the phototoxicity using Sprague-Dawley (SD) rats for transdermal administered drugs and we studied the appropriate UVA dose using 8-methoxypsalen, which is a well-known phototoxic drug. We found that a UVA dose of 15 J/cm2 was dose and time dependent response compared to other UVA doses. We performed the Minimum Erythema Dose (MED) test because UVB can cause skin irritation by itself and selected 0.01 J/cm2 as an appropriate dose of UVB. Using the selected UVA and UVB doses, we performed a phototoxicity study of 6 pharmaceutical drugs, which included phototoxic and non-phototoxic drugs. As a result of the phototoxicity test, 100% accuracy was obtained when compared with previous studies. In addition, we performed histopathology to confirm the new findings. We found that histopathology can be used as an additional indicator of phototoxicity test for transdermally administered drugs.

Evaluation of skin phototoxicity of transdermally administered pharmaceuticals in Sprague-Dawley rats / 한국실험동물학회지

Some drugs cause phototoxicity in humans when exposed to light, thus there is a need for an in vivo phototoxicity test to evaluate them. However, an in vivo phototoxicity test method to evaluate this has not been established. This study aimed to establish an in vivo phototoxicity test method for transdermally administered drugs. For this, we evaluated the phototoxicity using Sprague-Dawley (SD) rats for transdermal administered drugs and we studied the appropriate UVA dose using 8-methoxypsalen, which is a well-known phototoxic drug. We found that a UVA dose of 15 J/cm2 was dose and time dependent response compared to other UVA doses. We performed the Minimum Erythema Dose (MED) test because UVB can cause skin irritation by itself and selected 0.01 J/cm2 as an appropriate dose of UVB. Using the selected UVA and UVB doses, we performed a phototoxicity study of 6 pharmaceutical drugs, which included phototoxic and non-phototoxic drugs. As a result of the phototoxicity test, 100% accuracy was obtained when compared with previous studies. In addition, we performed histopathology to confirm the new findings. We found that histopathology can be used as an additional indicator of phototoxicity test for transdermally administered drugs.

Reduced Expression of YAP in Dermal Fibroblasts is Associated with Impaired Wound Healing in Type 2 Diabetic Mice

Dermal fibroblasts play essential roles in wound healing and their dysfunction has been shown to be associated with impaired wound healing in diabetes. In the present study, we aimed at investigating whether Yes-associated protein (YAP), a mediator of mechanotransduction in dermal fibroblasts, is associated with impaired wound healing in diabetic mice. Compared with that in the control, the rate of wound contraction was decreased twofold in db/db type 2 diabetic mice (db/db mice). To mimic diabetic pathological condition, dermal fibroblasts were cultured under high glucose conditions (25.5 mM glucose). Further, dermal fibroblast-mediated contraction of wound was evaluated by in vitro collagen gel contraction assay. Dermal fibroblasts cultured under hyperglycemic condition showed impaired gel contraction and mitochondrial dysfunction, compared to the cells cultured under normoglycemic conditions (5.5 mM glucose). Importantly, compared with the normal dermal fibroblasts, diabetic db/db dermal fibroblasts expressed lower levels of growth factors and cytokines that enhance wound healing, such as insulin-like growth factor-1, stromal cell-derived factor-1, connective tissue growth factor, and transforming growth factor-β (TGF-β). The quantity of YAP mRNA was also lower in diabetic db/db dermal fibroblasts, compared with that in the control fibroblasts. These results indicate that impaired wound healing in diabetics is associated with the dysfunction of dermal fibroblasts, including downregulation of YAP, which plays essential roles in extracellular matrix remodeling and TGF-β-mediated wound healing.

Substance P and Thiorphan Synergically Enhance Angiogenesis in Wound Healing

Impaired angiogenesis is a common pathological characteristic of chronic wounds. Therefore, the regulation of angiogenesis is important for proper tissue repair. It was reported that substance P (SP) accelerates wound healing in a skin injury model. SP is degraded by neutral endopeptidase (NEP). Our study shows that systemic co-treatment of SP and thiorphan, an inhibitor of NEP synergically increased the number of α-smooth muscle actin positive-blood vessels in skin wounds. However, there was no synergic improvement in wound contraction and extracellular matrix deposition. Therefore, inhibition of endogenous NEP activity by thiorphan treatment might modulate the effects of SP treatment specifically on accelerating angiogenesis during wound healing. However, the molecular mechanism(s) of the synergic increase in angiogenesis by SP and thiorphan treatment is still unknown.

Substance P Modulates Properties of Normal and Diabetic Dermal Fibroblasts

Dermal fibroblasts play essential roles in wound healing. However, they lose their normal regenerative functions under certain pathologic conditions such as in chronic diabetic wounds. Here, we show that substance P (SP) rescues the malfunctions of dermal fibroblasts in diabetes. SP increased the proliferation of diabetic dermal fibroblasts dose-dependently, although the effect was lower compared to the SP-stimulated proliferation of normal dermal fibroblasts. In contrast to normal dermal fibroblasts, SP increased the expression level of vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1 (SDF-1) in diabetic dermal fibroblast hence, rescuing their angiogenic potential. The cellular characteristics of diabetic dermal fibroblasts modulated by SP would be able to accelerate the wound healing process through faster wound contraction and improved angiogenesis in diabetic chronic wounds. Moreover, SP pretreatment into dermal fibroblasts isolated from diabetic patients would be a promising strategy to develop autologous cell therapy for treating diabetic chronic wounds.

Efficient Cultivation Conditions for Human Limbal Epithelial Cells

To compare the stem niche in different culture conditions of limbal epithelial cells, the suspended human limbal epithelial cells (HLECs) were seeded on the 3T3-pretreated plates and the other suspended cells were plated on amniotic membranes (AMs) which were either cryo-preserved or freeze-dried. All were cultured for 10 to 12 days. Reverse transcription-polymerase chain reaction (RT-PCR) for ATP-binding casette, subfamily G, member 2 (ABCG2), p63, cytokeratin 12, and connexin 43 were performed in cultivated HLECs and their expression levels were compared. The mRNA expression of all markers examined showed no statistically significant differences between the cells on cryo-preserved and on freeze-dried AM. The expression of p63 and cytokeratin 12 in cultivated cells on AMs were significantly lower than those in 3T3-cocultured cells on RT-PCR and immunofluorescent staining. Cultivated HLECs on AMs showed reduced proliferation and differentiation while maintaining stem-property regardless of the preservative method of AM.

Isolation of Putative Corneal Epithelial Stem Cells from Cultured Limbal Tissue

PURPOSE: To investigate methods of isolating putative corneal epithelial stem cells from cultured limbal tissue. METHODS: Three extraction techniques were compared to identify an efficient method of obtaining a large number of viable corneal epithelial stem cells from the limbus. Limbal tissues were extracted by incubation at 37 degrees C or 4 degrees C for 1 or 16 hours, respectively, with 1.2U/ml dispase/trypsin or by treatment with 0.05% trypsin and 0.01% ethyldiaminetetraacetic acid (EDTA) at 37 degrees C in single procedure. Collected cells were cultured on NIH/3T3-seeded plates, and colony forming efficiency (CFE) was evaluated. Fluorescence activated cell sorting (FACS) was performed with a Coulter EPICS 753 after incubation with Hoechst 33342 and propidium iodide (PI). Hoechst negative cells were obtained using gates exhibiting low Hoechst blue with a 424/44 nm BP filter. Gated cells of each fraction were re-cultured to assess the capability of colony formation. RESULTS: The mean numbers of viable cells obtained from treatment with dispase and trypsin was 3x10(4) cell/ml and 8.06x10(5) cell/ml at 37 degrees C and 4 degrees C incubations; the number increased to 1.21x10(6) cell/ml with a trypsin/EDTA treatment (p<0.05). CFE was 9.67+/-2.13% and 6.63+/-2.35% in rabbit and human cells, respectively. Likewise, the Hoechst negative fraction was 3.61+/-0.42% and 5.21+/-4.91% in rabbit and human cells, respectively. The sorted Hoechst negative cells were cultured through four passages, forming small round colonies. In rabbit cells, the CFEs of Hoechst negative and positive fractions after FACS, were 12.67+/-2.24% and 1.17+/-6.13%, respectively (p<0.05). CONCLUSIONS: Putative corneal epithelial stem cells were efficiently isolated from limbal tissue using a trypsin/EDTA extraction and FACS. This technique may be very useful in tissue engineered stem cell therapy.

Isolation of Putative Limbal Epithelial Stem Cells by Fluorescein Activated Cell Sorting

PURPOSE: To analyze the isolating pattern of slow cycling cells as putative limbal epithelial stem cells (PLESCs) using Hoechst exclusive cell sorting. METHODS: Rabbits were injected with 5-bromo-2-deoxyuridine (Brd U) 1 month prior to be sacrificed. After obtaining limbal tissues, fluorescence-activated cells were sorted on a Coulter EPICS 753 after they had been incubated with Hoechst 33342 and propidium iodide. Two different methods were applied to sort PLESCs. Side-population(Sp) cells were obtained using gates with dichroic mirror to detect low Hoechst blue and red after verapamil was treated. Hoechst negative cells were obtained using gates exhibiting low Hoechst blue with a 424/44 BP filter. Brd U-retaining cells were counted and their sizes were evaluated in each gated sample to compare isolating pattern of PLESCs in each method. RESULTS: The percentages of Sp cells and of the Hoechst negative fraction were 0.96 +/- 0.79% and 16.01 +/- 13.60%, respectively(p=0.021). Homogeneity and density of the small cells were higher in Hoechst negative fraction than in Sp cells. The percentage of Brd U-retaining cells was 47.36 +/- 10.34% and 47.14 +/- 14.94% in Sp cells and Hoechst negative fraction, respectively(p>0.05), and they were 10 times higher than in non-Sp and Hoechst positive fraction(p=0.000). CONCLUSIONS: Hoechst negative exclusion without verapamil more efficiently isolated PLESCs than Sp did.

p21Cip/WAF1 activation is an important factor for the ERK pathway dependent anti-proliferation of colorectal cancer cells

p21Cip/WAF1, an important regulator of cell proliferation, is induced by both p53- and extracellular signal regulated kinase (ERK) pathways. The induction of p21Cip/WAF1 occurs by prolonged activation of the ERKs caused by extracellular stimuli, such as zinc. However, not all the cells appeared to respond to ERK pathway dependent p21Cip/WAF1 induction. Here we investigated the cause of such difference using colorectal cancer cells. p21Cip/WAF1 induction and concomitant reduction of bromodeoxyuridine (BrdU) incorporation were observed by zinc treatment within HT-29 and DLD-1. However, HCT-116 cells with high endogenous p21Cip/WAF1 levels did not show any additional increment of p21Cip/WAF1 levels by zinc treatment and did maintain high BrdU incorporation level. The p21Cip/WAF1 induction by zinc depended upon prolonged activation of extracellular signal regulated kinase (ERK) was not observed in HCT-116 cells. The percentage of BrdU positive cells was 50% higher in p21Cip/WAF1 -/- HCT-116 cells compared to p21Cip/WAF1 +/+ HCT- 116 cells, and no cells induced p21Cip/WAF1 incorporated BrdU in its nucleus, yet confirming the importance of p21Cip/WAF1 induction in anti- proliferation. These results again support that p21Cip/WAF1 induction is a determinant in the regulation of colonic proliferation by the ERK pathway.

Molecular assembly of mitogen-activated protein kinase module in ras-transformed NIH3T3 cell line

The ras, is a G-like protein that controls the mitogen-activated protein kinase (MAPK) pathway involved in control and differentiation of cell growth. MAPK is a key component of its signaling pathway and the aberrant activation may play an important role in the transformation process. To better understand roles of ras in the activation of MAPKs, we have established ras transformed NIH3T3 fibroblast cell line, and analyzed the MAPK module. The ras transformed cells formed numerous spikes at the edges of cells and showed loss of contact inhibition. The levels of ERK1/2 MAPKs as revealed by Western blot analysis were not significantly different between ras transformed and non-transformed cells. However, phosphorylation of ERK MAPKs and the level of MEK were significantly increased although the heavily expressed level of Raf-1, an upstream component of MAPK pathway was unchanged in ras transformed NIH3T3 cells. The sedimentation profile of the MAPK module kinases in a glycerol gradient showed the presence of a rather homogeneous species of multimeric forms of ERK1/2 and MEK as indicated by the narrow distribution peak areas. The broad sedimentation profile of the Raf-1 in a glycerol gradient may suggest possible heterologous protein complexes but the identification of interacting molecules still remains to be identified in order to understand the organization of the MAPK signal transduction pathway.