Gene-specific somatic epigenetic mosaicism of FDFT1 underlies a non-hereditary localized form of porokeratosis

Porokeratosis is a clonal keratinization disorder characterized by solitary, linearly arranged, or generally distributed multiple skin lesions. Previous studies showed that genetic alterations in MVK, PMVK, MVD, or FDPS-genes in the mevalonate pathway-cause hereditary porokeratosis, with skin lesions harboring germline and lesion-specific somatic variants on opposite alleles. Here, we identified non-hereditary porokeratosis associated with epigenetic silencing of FDFT1, another gene in the mevalonate pathway. Skin lesions of the generalized form had germline and lesion-specific somatic variants on opposite alleles in FDFT1, representing FDFT1-associated hereditary porokeratosis identified in this study. Conversely, lesions of the solitary or linearly arranged localized form had somatic bi-allelic promoter hypermethylation or mono-allelic promoter hypermethylation with somatic genetic alterations on opposite alleles in FDFT1, indicating non-hereditary porokeratosis. FDFT1 localization was uniformly diminished within the lesions, and lesion-derived keratinocytes showed cholesterol dependence for cell growth and altered expression of genes related to cell-cycle and epidermal development, confirming that lesions form by clonal expansion of FDFT1-deficient keratinocytes. In some individuals with the localized form, gene-specific promoter hypermethylation of FDFT1 was detected in morphologically normal epidermis adjacent to methylation-related lesions but not distal to these lesions, suggesting that asymptomatic somatic epigenetic mosaicism of FDFT1 predisposes certain skin areas to the disease. Finally, consistent with its genetic etiology, topical statin treatment ameliorated lesions in FDFT1-deficient porokeratosis. In conclusion, we identified bi-allelic genetic and/or epigenetic alterations of FDFT1 as a cause of porokeratosis and shed light on the pathogenesis of skin mosaicism involving clonal expansion of epigenetically altered cells.

[J-TEC's efforts to industrialize regenerative medicine in Japan]

Japan Tissue Engineering Co., Ltd., J-TEC, was launched in 1999 to industrialize regenerative medicine in Japan. We developed the first regenerative medicine product, JACE (autologous cultured epidermis), which received PMDA approval for treating serious burns in 2007. Then, JACC (autologous cultured cartilage), the second product, was approved in 2012 for efficacy on traumatic cartilage defects. In 2014, the Pharmaceutical Affairs Law was revised to the Pharmaceutical and Medical Device Act, and regenerative medicine products, including gene therapies, were newly classified to accelerate productization. Subsequently, Nepic (autologous cultured corneal epithelium) and Ocural (autologous cultured oral mucosal epithelium) for epithelialization of limbal stem cell deficiencies in ophthalmology were approved in 2020 and 2021, respectively. Furthermore, a new product, JACEMIN (autologous cultured epidermis maintaining melanocyte) for vitiligo treatment was approved in 2023. We have developed five products of regenerative medicine that construct human tissues to graft rather than injectable cell suspensions like drugs. To develop regenerative medicine products, it is necessary to ensure the safety of raw materials, standardize the cultivation process, examine cell characteristics on GLP tests, construct transportation methods, build GCTP facilities, and conduct clinical trials on GCP. Re-examinations of JACE for serious burns and JACC for cartilage defects were completed after 7 years of all-case postmarketing surveillance. The commercialization of these products has become a benchmark for domestic regulation and has induced the development of a regenerative medicine industry promoted by Japan.

Agent-based approach for elucidating the release from collective arrest of cell motion in corneal epithelial cell sheet

Changes in cell fluidity have been observed in various cellular tissues and are strongly linked to biological phenomena such as self-organization. Recent studies suggested variety of mechanisms and factors, which are still being investigated. This study aimed to investigate changes in cell fluidity in multi-layered cell sheets, by exploring the collective arrest of cell motion and its release in cultures of corneal epithelial cells. We constructed mathematical models to simulate the behaviors of individual cells, including cell differentiation and time-dependent changes in cell-cell connections, which are defined by stochastic or kinetic rules. Changes in cell fluidity and cell sheet structures were expressed by simulating autonomous cell behaviors and interactions in tissues using an agent-based model. A single-cell level spatiotemporal analysis of cell state transition between migratable and non-migratable states revealed that the release from collective arrest of cell motion was initially triggered by a decreased ability to form cell-cell connections in the suprabasal layers, and was propagated by chain migration. Notably, the disruption of cell-cell connections and stratification occurred in the region of migratable state cells. Hence, a modeling approach that considers time-dependent changes in cell properties and behavior, and spatiotemporal analysis at the single-cell level can effectively delineate emergent phenomena arising from the complex interplay of cells.

A novel approach for wound treatment using dried cultured epidermal allograft: A phase I/II, single-center, open-label clinical trial

BACKGROUND

Autologous cultured epidermis (CE) is successfully used in burn care, but it requires a manufacturing time of three weeks and is very expensive owing to its custom-made nature of treatment. To compensate this disadvantage, dried allogeneic CE promises a novel therapeutic approach; and previous reports have demonstrated its efficacy in promoting wound healing using a murine skin defect model. Herein, a prospective clinical study was conducted to confirm the safety and efficacy of dried allogeneic CE for wound treatment.

METHODS

Dried CE was manufactured using donor keratinocytes obtained from excess surgical skin and applied to skin defects that were at least 3 cm in length and less than 10 % of the body surface area of the patients. The patients were observed for 14 days after CE application. The primary endpoint was the incidence of adverse events and the secondary endpoint was the percentage of wound healed since baseline, on days 7 and 14. Furthermore, as a stratified analysis, the percentage of wound healed, specified as deep dermal burns, was calculated.

RESULTS

Six patients (five burns and one skin ulcer after necrotizing fasciitis) enrolled in the study. As a serious adverse event, a local infection was observed in one patient, which resolved by debridement and conventional skin grafting. Other adverse events that were potentially related to this treatment included two cases of skin erosion, and one case of systemic fever. No unresolved adverse events remained at the end of the study period. The percentage of wound healed was 73.4 ± 19.2 % on Day 7, and 92.2 ± 11.8 % on Day 14. When the targeted disease was restricted to deep dermal burns, the percentage of wound healed was 69.9 ± 28.9 % on Day 7 and 90.5 ± 13.2 % on Day 14.

CONCLUSION

Treatment with dried CE was safely performed without any unresolved severe adverse effects. Dried CE is a new and promising modality for skin defect treatment, such as burns and ulcers, and is expected to compensate for the disadvantages of autologous CE. However, large-scale clinical trials are required to confirm their efficacy.

Dried human-cultured epidermis accelerates wound healing in a porcine partial-thickness skin defect model

Introduction

Autologous cultured epidermis (CE) is an effective approach for overcoming the deficiency of donor sites to treat extensive burns. However, the production of autologous CE takes 3-4 weeks, which prevents its use during the life-threatening period of severe burns. In contrast, allogeneic CE can be prepared in advance and used as a wound dressing, releasing several growth factors stimulating the activity of recipient cells at the application site. Dried CE is prepared by drying CEs under controlled temperature and humidity conditions until all the water is completely removed and no viable cells are present. Dried CE accelerates wound healing in a murine skin defect model and is potentially a new therapeutic strategy. However, the dried CE safety and efficacy have not yet been studied in large animal models. Therefore, we studied the safety and efficacy of human-dried CE in wound healing using a miniature swine model.

Methods

Human CE was manufactured using Green's method from donor keratinocytes. Three types of CEs (Fresh, Cryopreserved, and Dried) were prepared, and the ability of each CE to promote keratinocyte proliferation was confirmed in vitro. Extracts of the three CEs were added to keratinocytes seeded in 12-well plates, and cell proliferation was evaluated using the WST-8 assay for 7 days. Next, we prepared a partial-thickness skin defect on the back of a miniature swine and applied three types of human CE to evaluate wound healing promotion. On days 4 and 7, the specimens were harvested for hematoxylin-eosin, AZAN, and anti-CD31 staining to assess epithelialization, granulation tissue, and capillary formation.

Results

The conditioned medium containing dried CE extract significantly enhanced keratinocyte proliferation compared to the control group (P < 0.05). In vivo experiments revealed that human-dried CE significantly accelerated epithelialization at day 7 to the same extent as fresh CE, compared to the control group (P < 0.05). The three CE groups similarly affected granulation formation and neovascularization.

Conclusions

Dried CE accelerated epithelialization in a porcine partial-thickness skin defect model, suggesting that it may be an effective burn treatment alternative. A clinical study with a long-term follow-up is needed to assess the applicability of CEs in clinics.

Establishment of a keratinocyte and fibroblast bank for clinical applications in Japan

Regenerative medicine products using allogeneic cells, such as allogeneic cultured epidermis (allo-CE), have become a more critical therapeutic method for the treatment of burns. However, there are no clinically available allo-CE products in Japan. Therefore, establishing a quality-controlled cell bank is mandatory to create regenerative medical products using allogeneic cells. In this study, we selected ten patients from the Department of Plastic Surgery of Kyoto University Hospital to become cell donors. We performed medical interviews and blood sampling for the donor to ensure virus safety. We examined the tissues and isolated cells by performing a nucleic acid test (NAT). To establish a master cell bank, quality evaluation was performed according to the International Conference of Harmonization (ICH) Q5A. Serological tests of the blood samples from the ten donors showed that two of them were ineligible. The cells registered in the cell bank were found to be compatible after virus testing was performed, and a master cell bank was constructed. Hence, we established a keratinocyte and fibroblast bank of clinically usable human cultured cells in Japan for the first time.

Clinical Trial of Autologous Cultivated Limbal Epithelial Cell Sheet Transplantation for Patients with Limbal Stem Cell Deficiency

OBJECTIVE OR PURPOSE

To confirm the efficacy and safety of Good Manufacturing Practice (GMP)-compliant autologous cultivated limbal epithelial cell sheets in government-controlled clinical trials that adhered to Good Clinical Practice stipulations for patients with unilateral limbal stem cell deficiency (LSCD).

DESIGN

A prospective, multi-center, open-label, uncontrolled, single-arm clinical trial.

SUBJECTS, PARTICIPANTS OR CONTROLS

Ten consecutive eyes of 10 patients with unilateral LSCD were followed for two years after surgery. Preoperative LSCD stage was IIB in four eyes and III in six eyes.

METHODS

A limbal tissue biopsy was obtained from the healthy eye, after which limbal stem cells were dissociated and cultivated on temperature-responsive culture surfaces. All cell sheets were fabricated in a GMP-grade facility under established standard operating procedures. Cell sheets were evaluated using defined shipment criteria before transplantation, and only those that met the criteria were used. The cell sheet was transplanted onto each of the patients' diseased eye after removing the conjunctival scar tissue that covered the corneal surface. The severity of LSCD was determined according to a staging method agreed upon by global consensus, with eyes evaluated as being in stages IA-C representing successful corneal epithelial reconstruction. LSCD diagnosis and staging were determined by the trial's Eligibility Judgment Committee and Effect Assessment Committee using slit-lamp photographs including fluorescein staining. Both committees comprised two or three third-party cornea specialists, who were provided with information anonymously and randomly.

MAIN OUTCOME MEASURE

Corneal epithelial reconstruction rate was the primary endpoint.

RESULTS

Corneal epithelial reconstruction was successful in six of 10 eyes (60%) one year postoperatively and was significantly higher than the 15% clinically significant efficacy rate achieved by allogeneic limbal transplantation. The reconstruction rate was 70% of eyes two years postoperatively. Additionally, improvements in visual acuity were noted in 50% and 60% of eyes at one and two years, respectively. No clinically significant transplantation-related adverse events were observed.

CONCLUSION

The efficacy and safety of cultivated limbal epithelial cell sheet transplantation were thus confirmed, and the cell sheet, named Nepic, is now approved as a Cellular and Tissue-Based Product in Japan.

Dried human cultured epidermis accelerates wound healing in diabetic mouse skin defect wounds

Cryopreserved allogeneic cultured epidermis (CE) is used for treating second-degree burn wounds and diabetic foot ulcers; however, the need for cryopreservation limits its use. We have previously reported that CE accelerates wound healing irrespective of its viability and hypothesized that dehydrated CEs lacking living cells may act as an effective wound dressing. We prepared dried CE and investigated its morphological and physical properties and wound-healing effects and compared them with those of cryopreserved CE. Hematoxylin-eosin staining, immunostaining for basement membrane, and electron microscopy revealed that the morphologies of dried CE and cryopreserved CE were comparable and that the membrane structure was not damaged. The breaking strength, modulus of elasticity, and water permeability of dried CE were comparable with those of the cryopreserved CE. Furthermore, the levels of various active cytokines and chemokines in dried CE were comparable with those in cryopreserved CE. Dried CE applied to skin defect in diabetic mice significantly reduced the wound area and increased the new epithelium length 4 and 7 days after implantation, similar to that observed for cryopreserved CE. Consequently, dried CE had similar morphological and physical properties and wound-healing effects compared with those of cryopreserved CE and can be a physiological and versatile wound-dressing.

Cultured epidermal autografts for treatment of stable vitiligo: Quantitative analysis of color matching with surrounding normally pigmented skin

Cultured epidermal autografts (CEA) are surgical therapeutic alternatives for patients with stable vitiligo resistant to conventional medical treatments. In the present study, we assessed color matching before and at 12 months after CEA treatment. Eleven patients with 16 vitiligo lesions were included in this prospective study. The recipient sites were prepared by CO₂ laser superficial ablation and subjected to CEA application. We clinically evaluated and categorized the color matching of the repigmented skin as well as the percentage of repigmentation. We also obtained three color values (L*a*b*) for the vitiligo lesions and surrounding normally pigmented skin. We then calculated the color differences between the two regions and compared them before and at 12 months after treatment. The mean percentage of repigmentation was 63.3% at 12 months. Six of the 16 lesions were categorized as “same as” and had color difference values of ≤5 at 12 months after treatment. Clinical evaluation of the color matching coincided well with the calculated color difference values. CEA application after CO₂ laser superficial ablation was useful for treating vitiligo assessed by the percentage of repigmentation and color matching. Quantification of color differences may be a useful parameter for evaluating color matching in vitiligo.

Human cultured epidermis accelerates wound healing regardless of its viability in a diabetic mouse model

Allogeneic cultured epidermis (allo-CE) is a cultured keratinocyte sheet manufactured from donor cells and promotes wound healing when used in deep dermal burns, donor sites, and chronic ulcers and serves as a wound dressing. Allo-CE is usually cryopreserved to be ready to use. However, the cryopreservation procedure will damage the cell viability, and the influence of Allo-CE, according to its viability or wound healing process, has not been evaluated sufficiently. In this study, we aimed to prove the influence of keratinocyte viability contained in allo-CEs on wound healing. We prepared CEs with Green’s method using keratinocytes obtained from a polydactyly patient and then prepared four kinds of CEs with different cell viabilities [fresh, cryopreserved, frozen, and FT (freeze and thaw)]. The cell viabilities of fresh, cryopreserved, frozen, and FT CEs were 95.7%, 59.9%, 16.7%, and 0.0%, respectively. The four CEs had homogeneous characteristics, except for small gaps found in the FT sheet by transmission electron microscopy observation. The four CEs were applied on the full-thickness skin defect of diabetic mice (BKS.Cg-Dock 7^m +/+ Lepr^db/Jcl), and the wound area and neoepithelium length were evaluated on days 4, 7, and 14. As a result, FT CEs without viable cells similarly promoted epithelialization on days 4 and 7 (p<0.05) and accelerated wound closure on day 7 (p<0.01) as fresh CEs compared with the control group. In conclusion, the promoting effect of allo-CE on wound healing does not depend on cell viability. Lyophilized CEs may be a suitable wound dressing with a long storage period at room temperature.

Cell jamming, stratification and p63 expression in cultivated human corneal epithelial cell sheets

Corneal limbal epithelial stem cell transplantation using cultivated human corneal epithelial cell sheets has been used successfully to treat limbal stem cell deficiencies. Here we report an investigation into the quality of cultivated human corneal epithelial cell sheets using time-lapse imaging of the cell culture process every 20 minutes over 14 days to ascertain the level of cell jamming, a phenomenon in which cells become smaller, more rounded and less actively expansive. In parallel, we also assessed the expression of p63, an important corneal epithelial stem cell marker. The occurrence of cell jamming was variable and transient, but was invariably associated with a thickening and stratification of the cell sheet. p63 was present in all expanding cell sheets in the first 9 days of culture, but it's presence did not always correlate with stratification of the cell sheet. Nor did p63 expression necessarily persist in stratified cell sheets. An assessment of cell jamming, therefore, can shed significant light on the quality and regenerative potential of cultivated human corneal epithelial cell sheets.

Cultured Epidermal Autografts from Clinically Revertant Skin as a Potential Wound Treatment for Recessive Dystrophic Epidermolysis Bullosa

Inherited skin disorders have been reported recently to have sporadic normal-looking areas, where a portion of the keratinocytes have recovered from causative gene mutations (revertant mosaicism). We observed a case of recessive dystrophic epidermolysis bullosa treated with cultured epidermal autografts (CEAs), whose CEA-grafted site remained epithelized for 16 years. We proved that the CEA product and the grafted area included cells with revertant mosaicism. Based on these findings, we conducted an investigator-initiated clinical trial of CEAs from clinically revertant skin for recessive dystrophic epidermolysis bullosa. The donor sites were analyzed by genetic analysis, immunofluorescence, electron microscopy, and quantification of the reverted mRNA with deep sequencing. The primary endpoint was the ulcer epithelization rate per patient at 4 weeks after the last CEA application. Three patients with recessive dystrophic epidermolysis bullosa with 8 ulcers were enrolled, and the epithelization rate for each patient at the primary endpoint was 87.7%, 100%, and 57.0%, respectively. The clinical effects were found to persist for at least 76 weeks after CEA transplantation. One of the three patients had apparent revertant mosaicism in the donor skin and in the post-transplanted area. CEAs from clinically normal skin are a potentially well-tolerated treatment for recessive dystrophic epidermolysis bullosa.

Gene Expression and Methylation Analysis in Melanomas and Melanocytes From the Same Patient: Loss of NPM2 Expression Is a Potential Immunohistochemical Marker for Melanoma

DNA methylation is considered the primary epigenetic mechanism underlying the development of malignant melanoma. Since DNA methylation can be influenced by environmental factors, it is preferable to compare cancer and normal cells from the same patient. In order to compare the methylation status in melanoma tissues and melanocytes from the same individuals, we employed a novel epidermal sheet cultivation technique to isolate normal melanocytes from unaffected sites of melanoma patients. We also analyzed primary and metastatic melanoma samples, three commercially available melanocytes, and four melanoma cell lines. Cluster analysis of DNA methylation data classified freshly isolated melanomas and melanocytes into the same group, whereas the four melanoma cell lines were clustered together in a distant clade. Moreover, our analysis discovered methylation at several novel loci (KRTCAP3, AGAP2, ZNF490), in addition to those identified in previous studies (COL1A2, GPX3); however, the latter two were not observed in fresh melanoma samples. Subsequent studies revealed that NPM2 was hypermethylated and downregulated in melanomas, which was consistent with previous reports. In many normal melanocytes, NPM2 showed distinct immunohistochemical staining, while its expression was lost in malignant melanoma cells. In particular, intraepithelial lesions of malignant melanoma, an important challenge in clinical practice, could be distinguished from benign nevi. The present findings indicate the importance of using fresh melanoma samples, not melanoma cell lines and melanocytes in epigenetic studies. In addition, NPM2 immunoreactivity could be used to differentiate melanomas from normal melanocytes or benign disease.

Inactivation of Human Nevus Tissue Using High Hydrostatic Pressure for Autologous Skin Reconstruction: A Novel Treatment for Giant Congenital Melanocytic Nevi

Giant congenital melanocytic nevi are intractable lesions associated with a risk of melanoma. High hydrostatic pressure (HHP) technology is a safe physical method for producing decellularized tissues without chemicals. We have reported that HHP can inactivate cells present in various tissues without damaging the native extracellular matrix (ECM). The objectives of this study were to inactivate human nevus tissue using HHP and to explore the possibility of reconstructing skin using inactivated nevus in combination with cultured epidermis (CE). Human nevus specimens 8 mm in diameter were pressurized by HHP at 100, 200, 500, and 1000 MPa for 10 min. The viability of specimens just after HHP, outgrowth of cells, and viability after cultivation were evaluated to confirm the inactivation by HHP. Histological evaluation using hematoxylin-eosin staining and immunohistochemical staining for type IV collagen was performed to detect damage to the ECM of the nevus. The pressurized nevus was implanted into the subcutis of nude mice for 6 months to evaluate the retention of human cells. Then, human CE was applied on the pressurized nevus and implanted into the subcutis of nude mice. The viability of pressurized nevus was not detected just after HHP and after cultivation, and outgrowth of fibroblasts was not observed in the 200, 500, and 1000 MPa groups. Human cells were not observed after 6 months of implantation in these groups. No apparent damage to the ECM was detected in all groups; however, CE took on nevus in the 200 and 500 MPa groups, but not in the 1000 MPa group. These results indicate that human nevus tissue was inactivated by HHP at more than 200 MPa; however, HHP at 1000 MPa might cause damage that prevents the take of CE. In conclusion, all cells in nevus specimens were inactivated after HHP at more than 200 MPa and this inactivated nevus could be used as autologous dermis for covering full-thickness skin defects after nevus removal. HHP between 200 and 500 MPa will be optimal to reconstruct skin in combination with cultured epidermal autograft without damage to the ECM.

Preparation of Inactivated Human Skin Using High Hydrostatic Pressurization for Full-Thickness Skin Reconstruction

We have reported that high-hydrostatic-pressure (HHP) technology is safe and useful for producing various kinds of decellularized tissue. However, the preparation of decellularized or inactivated skin using HHP has not been reported. The objective of this study was thus to prepare inactivated skin from human skin using HHP, and to explore the appropriate conditions of pressurization to inactivate skin that can be used for skin reconstruction. Human skin samples of 8 mm in diameter were packed in bags filled with normal saline solution (NSS) or distilled water (DW), and then pressurized at 0, 100, 150, 200 and 1000 MPa for 10 minutes. The viability of skin after HHP was evaluated using WST-8 assay. Outgrowth cells from pressurized skin and the viability of pressurized skin after cultivation for 14 days were also evaluated. The pressurized skin was subjected to histological evaluation using hematoxylin and eosin staining, scanning electron microscopy (SEM), immunohistochemical staining of type IV collagen for the basement membrane of epidermis and capillaries, and immunohistochemical staining of von Willebrand factor (vWF) for capillaries. Then, human cultured epidermis (CE) was applied on the pressurized skin and implanted into the subcutis of nude mice; specimens were subsequently obtained 14 days after implantation. Skin samples pressurized at more than 200 MPa were inactivated in both NSS and DW. The basement membrane and capillaries remained intact in all groups according to histological and immunohistological evaluations, and collagen fibers showed no apparent damage by SEM. CE took on skin pressurized at 150 and 200 MPa after implantation, whereas it did not take on skin pressurized at 1000 MPa. These results indicate that human skin could be inactivated after pressurization at more than 200 MPa, but skin pressurized at 1000 MPa had some damage to the dermis that prevented the taking of CE. Therefore, pressurization at 200 MPa is optimal for preparing inactivated skin that can be used for skin reconstruction.

Long-term subculture of human keratinocytes under an anoxic condition

The serial subculturing of human keratinocyte cells under the anoxic and normoxic conditions was examined. The cumulative number of population doublings in the subcultures under the former condition increased 2.1-fold while maintaining an appreciable growth rate of cells, as compared with that under the latter condition. Moreover, the migration ability, which was estimated by the rotation rate of paired cells, was maintained accompanied by fully developed filopodia of F-actin filaments under the anoxic condition, despite of the poor development of stress fibers at the center of the cellular body. The cells passaged under the anoxic condition possessed the sufficient clonogenic potential to form epithelial sheets, supporting the view that the long-term subculture of keratinocytes under the anoxic condition can be applied for cell expansion in the practical production of epithelial sheets.

Combination of short-pulsed CO2 laser resurfacing and cultured epidermal sheet autografting in the treatment of vitiligo: a preliminary report

Cultured epidermal autografting has been employed in a variety of clinical treatments including vitiligo management. In this study, we successfully treated 2 patients with vitiligo using a short-pulsed CO2 laser and by grafting the autologous cultured epidermis. Small pieces of uninvolved skin (2 x 1 cm) were taken for cultivation from a pudendal or axillary area and were expanded into 2 pieces of epidermal sheets 100 cm. Before grafting, the lesions were abraded superficially using a short-pulsed CO2 laser with a computerized pattern generator. After successful grafting, repigmentation was visible within 1 to 2 months. One year after grafting, the skin color was almost the same as that of the surrounding normal skin. Thus, the combination of short-pulsed CO2 laser resurfacing and cultured epidermal grafting is a powerful option for treating an asymmetric and wide vitiliginous lesion.

Histamine H2 receptor antagonism by T-593: studies on cAMP generation in Hepa cells expressing histamine H2 receptor

Histamine H2 receptor antagonism by T-593 was investigated in Hepa cells expressing canine histamine H2 receptors. T-593 inhibited generation of cAMP in Hepa cells stimulated by 10(-5) mol/l histamine with an IC50 value of 2.3 x 10(-6) mol/l, (S)-(-)-T-593, one of the enantiomers comprising racemic T-593, inhibited cAMP generation with an IC50 value of 6.1 x 10(-7) mol/l. On the other hand, the other enantiomer (R)-(+)-T-593 exhibited only a negligible effect. Incubation of the cell with (S)-(-)-T-593 for 60 min depressed the maximal response of the concentration-response curve of histamine with a nonparallel rightward shift. The slope of a Schild plot was 1.27. In contrast, (S)-(-)-T-593 caused a parallel rightward shift of the curve, with a Schild plot slope that did not significantly differ from unity, by treating the cells for 15 min. The H2 receptor-blocking action of (S)-(-)-T-593 remained almost unaffected after washing out the drug, whereas the effect of ranitidine was reversible after washing. These results suggest that T-593 possesses a time-dependent insurmountable antagonistic action against histamine H2 receptor. T-593 may interact with the histamine H2 receptor molecule in a slowly associable and dissociable manner.

Histamine H2-receptor antagonism of T-593, an anti-ulcer agent: studies on aminopyrine accumulation in isolated canine gastric mucosal cells

Histamine H2-receptor antagonistic properties of the anti-ulcer agent T-593, (+/-)-(E)-1-[2-hydroxy-2-(4-hydroxyphenyl)ethyl] -3-[2[[[5-(methylamino)methyl-2-furyl]methyl]thio] ethyl] -2-(methylsulfonyl)guanidine, were investigated on [14C]aminopyrine accumulation in isolated canine gastric mucosal cells and compared with those of ranitidine and famotidine. The potency of T-593-inhibition of [14C]aminopyrine accumulation stimulated by 10(-4) M histamine, with an IC50 value of 1.85 x 10(-6) M, was approximately 5 times greater than that of ranitidine, but half that of famotidine. T-593 did not affect [14C]aminopyrine accumulation stimulated by carbachol or dibutyryl-cAMP. T-593 depressed the maximal response of the histamine concentration-response curve with a dose-related displacement to the right, indicating that the nature of the H2-receptor antagonism of T-593 was insurmountable and included non-competitive inhibition. The inhibitory efficacy of T-593 was time-dependent and was retained after the cells were washed. The inhibitory potency of (-)-S-T-593, one of the enantiomers, on the [14C]aminopyrine accumulation stimulated by histamine was approximately twice that of racemic T-593 and it also behaved as an insurmountable H2-receptor antagonist. However, the potency of (+)-R-T-593 was markedly weak. These results suggest that T-593 has H2-receptor antagonism that is insurmountable and this agent slowly associates and dissociates with the receptor in isolated canine gastric mucosal cells and that the specific substance causing H2-receptor antagonism is (-)-S-T-593.

The Cl- channel in hog gastric vesicles is part of the function of H,K-ATPase

Hog gastric vesicles showed Cl- conductance when treated with Cu2+-o-phenanthroline, an S-S cross-linking reagent. An IgG monoclonal antibody caused dose-dependent inhibition of Cl- conductance that had been induced by S-S cross-linking. The antibody did not cause intervesicular aggregation, as determined by measurement of vesicle size. These results show that Cl- conductance, the stimulation and inhibition of which are regulated reversibly by S-S----2SH transformation, is due to native, physiological channels. The antibody also dose dependently inhibited the activities of H,K-ATPase and p-nitrophenyl phosphatase in gastric vesicles, but did not inhibit Na,K-ATPase obtained from dog kidney. Immunoblotting with the antibody of vesicle proteins solubilized in sodium dodecyl sulfate-polyacrylamide gel showed that the antibody binds to a 95-kDa subunit of H,K-ATPase and its dimeric 180-kDa polypeptide. The antibody-binding sites of H,K-ATPase activity and the Cl- channel for the inhibition were present on the external (cytosolic) surface of the transmembraneous ATPase. A gastric antisecretory compound, 2-methyl-8-(phenylmethoxy)imidazo[1,2 alpha] pyridine-3-acetonitrile (SCH 28080), competitively bound to the high affinity site of K+ on the internal (luminal) surface of H,K-ATPase, and its half-maximal inhibitory concentration for H,K-ATPase activity in tight vesicles was 0.2 microM in the presence of valinomycin. SCH 28080 also dose dependently inhibited opening of Cl- channels by S-S cross-linking, the regulatory site being present on the cytosolic side and more internally than the antibody binding site. The half-inhibitory concentration of SCH 28080 was 0.3 microM. The present results with the antibody and SCH 28080 indicate that the Cl- channel is part of the function of H,K-ATPase.