Discovering a New Okadaic Acid Derivative, a Potent HIV Latency Reversing Agent from Prorocentrum lima PL11: Isolation, Structural Modification, and Mechanistic Study

Marine toxins (MTs) are a group of structurally complex natural products with unique toxicological and pharmacological activities. In the present study, two common shellfish toxins, okadaic acid (OA) (1) and OA methyl ester (2), were isolated from the cultured microalgae strain Prorocentrum lima PL11. OA can significantly activate the latent HIV but has severe toxicity. To obtain more tolerable and potent latency reversing agents (LRAs), we conducted the structural modification of OA by esterification, yielding one known compound (3) and four new derivatives (4–7). Flow cytometry-based HIV latency reversal activity screening showed that compound 7 possessed a stronger activity (EC50 = 46 ± 13.5 nM) but was less cytotoxic than OA. The preliminary structure–activity relationships (SARs) indicated that the carboxyl group in OA was essential for activity, while the esterification of carboxyl or free hydroxyls were beneficial for reducing cytotoxicity. A mechanistic study revealed that compound 7 promotes the dissociation of P-TEFb from the 7SK snRNP complex to reactivate latent HIV-1. Our study provides significant clues for OA-based HIV LRA discovery.

Homo/Hetero-Dimers of Aromatic Bisabolane Sesquiterpenoids with Neuroprotective Activity from the Fungus Aspergillus versicolor A18 from South China Sea

Chromatographic fractionation of the EtOH extracts of the marine-derived fungus Aspergillus versicolor A18 has led to the isolation of 11 homo/hetero-dimers of aromatic bisabolane sesquiterpenoids including eight diphenyl ether-coupled aromatic bisabolanes (1a/1b and 5−10) and three homodimers (2−4), together with their monomers including three aromatic bisabolanes (11−13) and two diphenyl ethers (14 and 15). Their structures and absolute configurations were elucidated by extensive spectroscopic analysis including HRESIMS, 1D/2D NMR, calculated ECD, and the optical rotatory data. Among the four new compounds, (+/−)-asperbisabol A (1a/1b), asperbisabol B (2), and asperbisabol C (3), the enantiomers 1a and 1b represent an unprecedented skeleton of diphenyl ether-coupled aromatic bisabolane sesquiterpenoids with a spiroketal core moiety. The neuroprotective effects of selected compounds against sodium nitroprusside (SNP)-induced injury were evaluated in PC12 cells by the MTT assay. Five compounds (1a, 6, and 8−10) showed remarkable neuroprotective activities at 10 μM, being more active than the positive control edaravone.

Germ plasm and the origin of the primordial germ cells in the oriental river prawn Macrobrachium nipponense

Germ plasm is a special cytoplasmic component containing special RNAs and proteins, and is located in specific regions of oocytes and embryos. Only the blastomeres inheriting the germ plasm can develop into primordial germ cells (PGCs). By using Vasa mRNA as a germline marker, we previously demonstrated that germline specification followed the preformation mode in the prawn Macrobrachium nipponense. In this study, we raised the Vasa antibody to identify germ plasm in the oocyte and trace the origin and migration of PGCs. In previtellogenic oocytes, Vasa protein was detected in the perinuclear region, in which electron-dense granules associated with numerous mitochondria were mostly visualized under a transmission electron microscope. In mature oocytes, immunosignal was localized to a large granule under the plasma membrane. During early embryogenesis, the granule was inherited by a single blastomere from 1-cell to 16-cell stages, and thereafter was segregated into two daughter blastomeres at the 32-cell stage. In gastrula, the Vasa-positive cells were large with typical PGC characteristics, containing a big round nucleus and a prominent nucleolus. The immunosignal was localized to the perinuclear region again. In the zoea stage, the Vasa-positive cells migrated toward the genital ridge and clustered in the dorsomedial region close to the yolk portion. Accordingly, we concluded that the prawn PGCs could be specified from the 16-cell stage by inheriting the germplasm. To our knowledge, this is the first report on the identification of the prawn germ plasm and PGCs. The continuous expression of Vasa protein throughout oogenesis and embryogenesis suggests that Vasa protein could be an important factor in germ plasm that functions in early germ cell specification.

Research Progress on Secondary Metabolites from the Ascidians of Aplidium Genus

Abstract:

Ascidians (tunicates) are widely recognized as one of the most prolific producers of bioactive natural products in the marine environment. This present study reviewed the chemical diversity of marine ascidians from the Aplidium genus and their pharmacological applications since Jan 2005. The resources of this genus from China Seas, including the changes of their names in the family Polydinidae were also summarized in this paper. In addition, a concise outlook on their chemical and pharmaceutical investigation is made to support further development.

Eosinophilic gastroenteritis with abdominal pain and ascites: A case report

BACKGROUND

Eosinophilic gastroenteritis (EGE) is a rare disease that presents many unspecific gastroenterological symptoms. The disease includes three types depending on the depth of eosinophil infiltration in the gastrointestinal tract. The serosal type is the most rare, presenting as ascites.

CASE SUMMARY

A 34-year-old man presented with abdominal pain, diarrhea without bloody stool, or nausea. Laboratory test results revealed a peripheral blood eosinophil count (4.85 × 10⁹/L), which was remarkedly elevated. Computed tomography scan demonstrated extensive intestinal wall edema thickening in the duodenum, jejunum, ascending colon and transverse colon; multiple exudative effusion surrounding the intestinal tract, and ascites in the abdominal cavity. A series of examinations excluded eosinophil elevation in secondary diseases. Endoscopic multipoint biopsy detected eosinophilic infiltration in the mucous layer of the transverse colon, with ≥ 50 eosinophils/high power field. All symptoms vanished after a few days of steroid therapy and ascites disappeared within 2 wk.

CONCLUSION

EGE should be considered in patients with abdominal pain, ascites, and eosinophilia. Multiple point biopsies are essential for diagnosis.

Identification of a novel germ cell marker MnTdrd from the oriental river prawn Macrobrachium nipponense

Germ cell-specific genes play an important role in establishing the reproductive system in sexual organisms and have been used as valuable markers for studying gametogenesis and sex differentiation. Previously, we isolated a vasa transcript as a germ cell marker to trace the origin and migration of germ cells in the oriental river prawn Macrobrachium nipponense. Here, we identified a new germ cell-specific marker MnTdrd RNA and assessed its temporal and spatial expression during oogenesis and embryogenesis. MnTdrd transcripts were expressed in high abundance in unfertilized eggs and embryos at cleavage stage and then dropped significantly during late embryogenesis, suggesting that MnTdrd mRNA is maternally inherited. In situ hybridization of ovarian tissue showed that MnTdrd mRNA was initially present in the cytoplasm of previtellogenic oocyte and localized to the perinuclear region as the accumulation of yolk in vitellogenic oocyte. Whole-mount in situ hybridization of embryos showed that MnTdrd-positive signals were only localized in one blastomere until 16-cell stage. In the blastula, there were approximately 16 MnTdrd-positive blastomeres. During embryonized-zoea stage, the MnTdrd-positive cells aggregated as a cluster and migrated to the genital rudiment which would develop into primordial germ cells (PGCs). The localized expression pattern of MnTdrd transcripts resembled that of the previously identified germ cell marker vasa, supporting the preformation mode of germ cell specification. Therefore, we concluded that MnTdrd, together with vasa, is a component of the germ plasm and might have critical roles in germ cell formation and differentiation in the prawn. Thus, MnTdrd can be used as a novel germ cell marker to trace the origin and migration of germ cells.

Hexagonal layered group IV-VI semiconductors and derivatives: fresh blood of the 2D family

New phases of group IV-VI semiconductors in 2D hexagonal structures are predicted and their unusual physical properties are revealed. The structures of monolayer group IV-VI semiconductors are similar to those of blue phosphorene and each unit has the same ten valence electrons. The band gap of 2D hexagonal group IV-VI semiconductors depends on both the thickness and stacking order. Atomic functionalization can induce ferromagnetism, and the Curie temperature can be tuned. Gapped Dirac fermions with zero mass are developed and this makes it exceed that of graphene. The Fermi velocity can be compared to or even above that of graphene.

The in vitro and vivo anti-tumor effects and molecular mechanisms of suberoylanilide hydroxamic acid (SAHA) and MG132 on the aggressive phenotypes of gastric cancer cells

Here, we found that both SAHA and MG132 synergistically inhibited proliferation, glycolysis and mitochondrial oxidization, induced cell cycle arrest and apoptosis in MGC-803 and MKN28 cells. SAHA increased cell migration and invasionat a low concentration. SAHA induced the overexpression of acetyl histone 3 and 4, which were recruited to p21, p27, Cyclin D1, c-myc and nanog promoters to transcriptionally up-regulate the former two and down-regulate the latter three. The expression of acetyl-histone 3 and 4 was increased during gastric carcinogenesis and positively correlated with cancer differentiation. SAHA and MG132 exposure suppressed tumor growth by inhibiting proliferation and inducing apoptosis in nude mice, increased serum ALT and AST levels and decreased hemaglobin level, white blood cell and neutrophil numbers. These data indicated that SAHA and MG132 in vivo and vitro synergistically induced cytotoxicity and apoptosis, suppressed proliferation, growth, migration and invasion of gastric cancer cells. Therefore, they might potentially be employed as chemotherapeutic agents if the hepatic injury and the killing effects of peripheral blood cells are avoided or ameliorated.

Highly Tunable Electronic Structures of Phosphorene/Carbon Nanotube Heterostructures through External Electric Field and Atomic Intercalation

Black phosphorene (BP)/carbon nanotube (CNT) heterostructures can be classified as either type I or II, depending on the size of the CNTs. An external electric field (E_ext) can modulate the interfacial electronic structures and separate the electron and hole carriers of the BP/CNT heterostructures. The giant Stark effect is observed, and the band gap of the semiconducting heterostructures can vary several-fold. The intercalation of 3d transition metals can strongly bond BP and CNTs together. Furthermore, strong ferromagnetism with Curie temperature (T_C) above room temperature is predicted. It is expected that these BP/CNT heterostructures will provide new opportunities and applications in the fields of optoelectronics and electronics as well as spintronics.

Efficient Split-Lanczos propagator for strong-field ionization of atoms

High angular momentum partial waves are indispensable in the numerical calculations of the time-dependent Schrödinger equation (TDSE) for the interaction between atoms and strong long-wavelength laser pulses. In these cases, the widely-applied Lanczos propagator, used to solve the TDSE, requires an extremely small time step to be convergent. By splitting out the centrifugal potential from the whole Hamiltonian, we demonstrate that the stiffness of the TDSE can be reduced and a rather large time step is allowed for the present Split-Lanczos propagator. Compared with the ordinary Lanczos propagator, the efficiency of the propagation can be improved by more than 100 times for large angular momentum in present tests.

Downregulation of ZNF278 arrests the cell cycle and decreases the proliferation of colorectal cancer cells via inhibition of the ERK/MAPK pathway

Zinc finger protein 278 is a zinc finger transcription factor encoded on the 22q12.2 chromosome. Previous studies revealed that ZNF278 expression was significantly upregulated in colorectal cancer (CRC) tissue compared to adjacent non-tumor tissue. However, the expression and specific roles of ZNF278 in CRC remain unknown. ZNF278 expression was knocked down using specific siRNAs, which was confirmed by western blotting, and the effects of ZNF278 siRNAs on CRC cell proliferation were investigated. In addition, the effects of ZNF278 overexpression were confirmed by western blotting and cell proliferation assay. Correlations between ZNF278 and the ERK/MAPK pathway were also detected by western blotting. We found that ZNF278 knockdown significantly induced cell cycle arrest, resulting in cyclin D1/E1 downregulation and p21 upregulation. Moreover, we demonstrated that downregulation of ZNF278 decreased the proliferation of CRC cells via inhibition of the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) pathway for the first time. In conclusion, ZNF278 played a prominent role in the pathogenesis of CRC, and promoted CRC cell proliferation via the ERK/MAPK pathway, suggesting that it may act as a potential target in the diagnosis or treatment of CRC.

Unusual Cytotoxic Steroidal Saponins from the Gorgonian Astrogorgia dumbea

Three steroidal saponins, including astrogorgiosides A (1) and B (2) bearing acetamido-glucose moieties, and astrogorgioside C (3) with a 19-nor and bearing an aromatized B ring steroid aglycone, together with a known major saponin dimorphoside A (4), were obtained from the gorgonian Astrogorgia dumbea collected near Dongshan Island in East China Sea. Structures of these compounds were elucidated by in-depth spectral and chemical methods, including 2D-NMR, HR-ESI-MS spectra, and acidic hydrolysis. For the first time, acetamido-glucose moiety is being reported from a gorgonian. The B-ring aromatized steroid aglycone of compound 3 is also rare in marine natural products. Compounds 1-3 exhibited moderate cytotoxic activity with IC50 values of 26.8-45.6 µM against human tumor cells Bel-7402 and K562.

Screening of potential diagnostic markers and therapeutic targets against colorectal cancer

Objective

To identify genes with aberrant promoter methylation for developing novel diagnostic markers and therapeutic targets against primary colorectal cancer (CRC).

Methods

Two paired CRC and adjacent normal tissues were collected from two CRC patients. A Resi: MBD2b protein-sepharose-4B column was used to enrich the methylated DNA fragments. Difference in the average methylation level of each DNA methylation region between the tumor and control samples was determined by log₂ fold change (FC) in each patient to screen the differentially methylated DNA regions. Genes with log₂FC value ≥4 or ≤−4 were identified to be hypermethylated and hypomethylated, respectively. Then, the underlying functions of methylated genes were speculated by Gene Ontology database and pathway enrichment analyses. Furthermore, a protein–protein interaction network was built using Search Tool for the Retrieval of Interacting Genes/Proteins database, and the transcription factor binding sites were screened via the Encyclopedia of DNA Elements (ENCODE) database.

Results

Totally, 2,284 and 1,142 genes were predicted to have aberrant promoter hypermethylation or hypomethylation, respectively. MAP3K5, MAP3K8, MAPK14, and MAPK9 with promoter hypermethylation functioned via MAPK signaling pathway, focal adhesion, or Wnt signaling pathway, whereas MAP2K1, MAPK3, MAPK11, and MAPK7 with promoter hypomethylation functioned via TGF-beta signaling pathway, neurotrophin signaling pathway, and chemokine signaling pathway. CREBBP, PIK3R1, MAPK14, APP, ESR1, MAPK3, and HRAS were the seven hubs in the constructed protein–protein interaction network. RPL22, RPL36, RPLP2, RPS7, and RPS9 were commonly regulated by transcription factors, and YY1 and IRF4 were hypermethylated.

Conclusion

MAPK14, MAPK3, HRAS, YY1, and IRF4 may be considered as potential biomarkers for early diagnosis and therapy of CRC.

[Purine and carboline alkaloids from ascidian Symplegma oceania]

Five purine and carboline alkaloids were isolated from the methanol extract of the ascidian Symplegma oceania. Classic chromatographies including preparative HPLC were used for isolation and purification of the compounds. The structures were established as 6-methoxy-7-methyl-8-oxoguanine (1), 2-methylimino-3-methyl-6-methylamino- 9H-purine (2), 1,2,3,4-tetrahydro-betacarboline (3), 1,2,3,4-tetrahydro-1-methyl-beta-carboline (4) and 1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (5) by comparison the spectroscopic data (MS, 1H, 13C-NMR) with those reported in the literatures. Compounds 2-5 were reported from the the genus Symplegma for the first time. The purine and carboline were the major alkaloid types of S. oceania.

mTOR signaling pathway is a target for the treatment of colorectal cancer

BACKGROUND

mTOR signaling has been suggested to be an important factor involved in tumorigenesis, but its role in human colorectal cancer (CRC) has not been completely elucidated. Herein, the purpose of this study was to analyze the distribution pattern of mTOR signaling components in CRC and adenoma and to determine whether targeted inhibition of mTOR could be a potential therapeutic strategy for CRC.

METHODS

Immunohistochemical analysis was performed on human CRC and adenoma for mTOR signaling components, including mTOR, p70s6 K, and 4EBP1. HCT116 and SW480 human CRC cell lines were treated with siRNA directed against mTOR, and cell viability, cell cycle, and apoptosis were assessed. HCT116 and SW480 cells were injected into athymic nude mice to establish a CRC xenograft model. Mice were randomly transfected with either nontargeting control or mTOR siRNA, and tumor volume, mTOR signaling activity, and apoptosis were evaluated.

RESULTS

mTOR signaling components, including mTOR, p70s6 K, and 4EBP1, were highly activated in glandular elements of CRC and colorectal adenomas with high-grade intraepithelial neoplasia (HIN), with a correlation between staining intensity and depth of infiltration in CRC. Inhibition of mTOR expression using a specific mTOR siRNA resulted in considerably decreased in vitro and in vivo cell growth.

CONCLUSIONS

mTOR signaling is associated with the clinical pathological parameters of human CRC. siRNA-mediated gene silencing of mTOR may be a novel therapeutic strategy for CRC.

Combined inhibition of Dnmt and mTOR signaling inhibits formation and growth of colorectal cancer

BACKGROUND AND AIMS

Although the anticancer effects of rapamycin (RPM) and 5-aza-deoxycytidine (AZA) have been studied extensively, the combined effect of these two drugs on colorectal cancer (CRC) is still unknown. This study addresses the effect of AZA and RPM combination therapy on CRC and its influence on the mammalian target of rapamycin (mTOR) and its signal transduction pathway.

SUBJECTS AND METHODS

Human CRC cell line HCT116 was treated with AZA alone, RPM alone, or concurrently with a combination of both drugs. Cell viability, apoptosis, and cell cycle distribution were analyzed. CRC was initiated in S-ICR mice, which were then treated with the drugs mentioned above, and tumor incidence and volume were measured. The activity of the mTOR signal transduction pathway was detected by Western blot analysis or immunohistochemistry.

RESULTS

Combination treatment with AZA and RPM inhibited the growth of HCT116 cells, induced apoptosis, arrested the cell cycle, and reduced the incidence and tumor volume of CRC in mice, as well as inhibited the phosphorylation of components of the mTOR signal transduction pathway. These effects were more significant than those of single-drug treatments.

CONCLUSION

Combination treatment with AZA and RPM inhibits the formation and growth of CRC. These findings may provide a novel strategy for CRC treatment.

Combined inhibition of MEK and mTOR signaling inhibits initiation and progression of colorectal cancer

The role of the mTOR signal pathway in colorectal cancer (CRC) pathogenesis remains unclear, and the combination effect of PD98059 (an inhibitor for MEK) and rapamycin (an inhibitor for mTOR) on CRC is still unknown. Here, we found that combination treatment with PD98059 and rapamycin suppressed the proliferation of CRC cells, induced apoptosis, arrested cell cycle, and reduced the incidence and volume of CRC in mice, as well as inhibited phosphorylation of mTOR and the MEK signal pathway components, of which the effects were more significant than single-drug treatments. These findings indicate that PD98059 combined with rapamycin appears to be a promising strategy for inhibiting the initiation, and progression of CRC, which may provide a novel strategy for CRC prevention.

Folic acid and sodium butyrate prevent tumorigenesis in a mouse model of colorectal cancer

Colorectal cancer is a leading cause of morbidity and mortality worldwide, and its incidence has been increasing in recent years. The role of epigenetic modifications, including DNA methylation and histone modifications, has only recently been investigated. In this study, the effects of epigenetic agents such as folic acid (FA) and sodium butyrate (NaBu) on the development of colorectal cancer induced by 1,2-dimethylhydrazine (DMH) using ICR mice was examined. Of the mice treated in a chemopreventive manner with epigenetic agents, FA and NaBu, 15-50% developed colorectal cancer at 24 weeks compared with a 95% incidence of colorectal cancer in DMH-treated control mice. Folate deficiency can alter cytosine methylation in DNA leading to inappropriate activation of the proto-oncogene c-myc. We detected lower levels of p21(WAF1) gene expression in colorectal cancer samples, as well as significantly lower levels of acetylated histone H3, compared with samples from corresponding normal colorectal mucosa. In contrast, administration of NaBu increased levels of p21(WAF1) mRNA and p21(WAF1) protein, and was associated with an accumulation of histone acetylation. In summary, our results show that FA and NaBu reduce the incidence of colorectal cancer induced by DMH-induced in ICR mice, and therefore we hypothesize that targeting epigenetic targets should be further investigated for the prevention of colorectal cancer in humans.

Inhibition of the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway decreases DNA methylation in colon cancer cells

The extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK-MAPK) pathway is a critical intermediary for cell proliferation, differentiation, and survival. In the human colon cancer cell line SW1116, treatment with the DNA methyltransferase 1 (DNMT1) inhibitor 5-aza-2'-deoxycytidine (5-aza-dC) or the ERK-MAPK inhibitors PD98059 or rottlerin, or transient transfection with the MAP/ERK kinase (MEK)1/2 small interfering RNA down-regulates DNMT1 and proliferating cell nuclear antigen levels. In this report, we found that drug treatment or small interfering RNA transfection of SW1116 cells induced promoter demethylation of the p16(INK4A) and p21(WAF1) genes, which up-regulated their mRNA and protein expression levels. Flow cytometry revealed that rottlerin treatment induced cell cycle arrest at phase G(1) (p < 0.05). Thus, the ERK-MAPK inhibitor treatment or siRNA-mediated knockdown of ERK-MAPK decreases DNA methylation via down-regulating DNMT1 expression and other unknown mediator(s) in SW1116 colon cancer cells.

A human skin equivalent model that mimics the photoproduction of vitamin D3 in human skin

A human skin equivalent was prepared by culturing human keratinocytes on the surface of nylon filtration meshes containing human skin fibroblasts and by growing the epidermal cells at the air-liquid interface. This human skin equivalent model was used to mimic the photoproduction of vitamin D3 in human skin. It was found that the concentration of 7-dehydrocholesterol and its photoconversion to previtamin D3 and its subsequent thermal isomerization to vitamin D3 in the human skin equivalent was essentially identical to that of human skin. The 7-dehydrocholesterol content in the skin equivalent and human skin was 2187 +/- 296 and 2352 +/- 320 ng/cm2, respectively. The percentage of the major photoproducts of 7-dehydrocholesterol in the skin equivalent following ultraviolet B radiation (0.5 J/cm2) was 35% pre-vitamin D3, 29% lumisterol, and 6% tachysterol; 30% remained as 7-dehydrocholesterol. Similarly, in human skin they were 36%, 29%, 7%, and 28%, respectively. After incubation at 37 degrees C for 30 min, 11% and 12% of the previtamin D3 had thermally isomerized to vitamin D3 in the skin equivalent and human skin. In conclusion, compared with cultured keratinocytes or fibroblasts, the human skin equivalent model provides a superior in vitro system that better mimics the physiology and biochemistry of the photosynthesis of vitamin D3 in human skin.

A liposomal model that mimics the cutaneous production of vitamin D3. Studies of the mechanism of the membrane-enhanced thermal isomerization of previtamin D3 to vitamin D3

We reported previously that the rate of previtamin D3 (preD3) <==> vitamin D3 isomerization was enhanced by about 10 times in the skin compared with that in organic solvents. To elucidate the mechanism by which the rate of this reaction is enhanced in the skin, we developed a liposomal model that mimicked the enhanced isomerization of preD3 to vitamin D3 that was described in human skin. Using this model we studied the effect of changing the polarity of preD3 as well as changing the chain length and the degree of saturation of liposomal phospholipids on the kinetics of preD3 <==> vitamin D3 isomerization. We found that a decrease in the hydrophilic interaction of the preD3 with liposomal phospholipids by an esterification of the 3beta-hydroxy of preD3 (previtamin D3-3beta-acetate) reduced the rate of the isomerization by 67%. The addition of a hydroxyl on C-25 of the hydrophobic side chain (25-hydroxyprevitamin D3), which decreased the hydrophobic interaction of preD3 with the phospholipids, reduced the rate by 87%. In contrast, in an isotropic n-hexane solution, there was little difference among the rates of the conversion of preD3, its 3beta-acetate, and 25-hydroxy derivatives to their corresponding vitamin D3 compounds. We also determined rate constants (k) of preD3 <==> vitamin D3 isomerization in liposomes containing phosphatidylcholines with different carbon chain lengths. The rates of the reaction were found to be enhanced as the number of carbons (Cn) in the hydrocarbon chain of the phospholipids increased from 10 to 18. In conclusion, these results support our hypothesis that amphipathic interactions between preD3 and membrane phospholipids stabilize preD3 in its "cholesterol like" cZc-conformer, the only conformer of preD3 that can convert to vitamin D3. The stronger these interactions were, the more preD3 was likely in its cZc conformation at any moment and the faster was the rate of its conversion to vitamin D3.

1,25-dihydroxyvitamin D3: a novel agent for enhancing wound healing

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3), has diverse effects in a variety of tissues and cell types, including skin. Since 1,25(OH)2D3 affects both fibroblast and keratinocytes, we evaluated the effect of 1,25(OH)2D3 on wound healing. We investigated the effect of the topically applied 1,25(OH)2D3 or vehicle on the healing of cutaneous wounds in rats in a blinded manner. Wound areas were measured by planimetry technique. Healing was expressed as the percentage of the original wound area that was healed. 1,25(OH)2D3 at concentrations between 5 and 50 ng/day caused a dose-dependent acceleration of healing. Time course and specificity studies indicated that 1,25(OH)2D3 specifically promoted healing between 1-5 days after wounding as compared with vitamin D (0.5 microgram/day), which showed no significant improvement over control. Our results suggest that 1,25(OH)2D3 and its analogues may be a new class of compounds that could be developed to enhance wound healing.

Catalyzed thermal isomerization between previtamin D3 and vitamin D3 via beta-cyclodextrin complexation

To examine the effect of microenvironments on previtamin D3<==>vitamin D3 isomerization, we have conducted kinetic studies of the reaction in an aqueous solution of beta-cyclodextrin. Our results showed that at 5 degrees C, the forward (k1) and reverse (k2) rate constants for previtamin D3<==>vitamin D3 isomerization were increased by more than 40 and 600 times, respectively, compared with those in n-hexane (k1, 8.65 x 10(-6) versus 1.76 x 10(-7) s-1; k2, 8.48 x 10(-6) versus 1.40 x 10(-8) s-1), the fastest rate of this isomerization ever reported at this temperature. Thermodynamic studies revealed that the equilibrium constant of the reaction was significantly reduced by more than 12-fold when compared to that in n-hexane at 5 degrees C, and the percentage of vitamin D3 at equilibrium was increased as the temperature was increased in beta-cyclodextrin. When complexed with beta-cyclodextrin, the previtamin D3<==>vitamin D3 isomerization became endothermic (delta H zero = 13.05 kJ mol-1) in contrast to being exothermic in other media. We propose that thermodynamically unfavorable cZc conformers of previtamin D3 are stabilized by beta-cyclodextrin, and thus the rate of the isomerization is increased. This conformation-controlled process may play an important role in the modulation of previtamin D3<==>vitamin D3 endocrine system in vivo such as in the sea urchin.

Evolutionary importance for the membrane enhancement of the production of vitamin D3 in the skin of poikilothermic animals

The photoproduction of vitamin D in the skin was essential for the evolutionary development of terrestrial vertebrates. During exposure to sunlight, previtamin D3 formed in the skin is isomerized to vitamin D3 (calciol) by a temperature-dependent process. Since early land vertebrates were poikilothermic, the relatively slow conversion of previtamin D3 to vitamin D3 at ambient temperature put them at serious risk for developing vitamin D deficiency, thus leading to a poorly mineralized skeleton that could have ultimately halted further evolutionary development of vertebrates on land. We evaluated the rate of isomerization of previtamin D3 to vitamin D3 in the skin of iguanas and found the isomerization rate was enhanced by 1100% and 1700% at 25 degrees C and 5 degrees C, respectively. It is likely that the membrane entrapment of previtamin D3 in its s-cis,s-cis conformation is responsible for the markedly enhanced conversion of previtamin D3 to vitamin D3. The membrane-enhanced production of vitamin D3 ensures the critical supply of vitamin D3 to poikilothermic animals such as iguanas.

Characterization of the translocation process of vitamin D3 from the skin into the circulation

The cutaneous synthesis of vitamin D3 and the subsequent translocation of vitamin D3 into the circulation are two key steps in the vitamin D endocrine system. To study the kinetic aspects of cutaneous synthesis and translocation of vitamin D3, both in vitro and in vivo chicken models have been developed. To assess the capacity of chicken skin to generate vitamin D3, the concentrations of 7-dehydrocholesterol (7-DHC) in different skin areas were determined. It was found that the highest concentration of 7-DHC was in the leg skin (3524 +/- 937 ng cm-2), which was about 30 times greater than that in the back (120 +/- 62 ng cm-2). Whole body exposure of chickens to UV-B radiation (0.5 J cm-2) resulted in the production of previtamin D3 (preD3) in the skin of the legs and feet (43 +/- 7 and 54 +/- 17 ng cm-2, respectively), whereas no preD3 was detected in the back skin. In vitro, at 40 C, the forward (k1) and reverse (k2) rate constants of the preD3<-->vitamin D3 reaction in the leg skin were greatly increased compared to those in n-hexane (k1, 0.367 vs. 0.0369 h-1; k2, 0.042 vs. 0.0059 h-1). In vivo, the determined rate constants k1, k2, and k3 for the consecutive reactions preD3<-->vitamin D3-->vitamin D3 were 0.257, 0.034, and 0.114 h-1, respectively. To evaluate the circulating concentration of vitamin D3 in response to UV-B radiation, chicken legs were irradiated. The time course revealed a 4-fold increase in the circulating concentration of vitamin D3, with a peak about 30 h postradiation. No appreciable amount of preD3 could be detected in the circulation in the early hours after UV-B radiation, suggesting the existence of a process responsible for the specific translocation of vitamin D3 from the skin into the circulation.

Kinetic and thermodynamic studies of the conversion of previtamin D3 to vitamin D3 in human skin

The thermoisomerization of previtamin D3 to vitamin D3 is the last step in the synthesis of vitamin D3 in human skin. Kinetic and thermodynamic studies of this reaction in human skin and an organic solvent revealed that not only the equilibrium of the reaction was shifted in favor of vitamin D3 formation in human skin (equilibrium constant K at 37 degrees C = 11.44) compared to hexane (K = 6.15), but also the rate of the reaction was increased by more than 10-fold in human skin (T1/2 at 37 degrees C = 2.5 h) when compared to hexane (T1/2 = 30 30 h). This extraordinarily fast reaction rate was also confirmed in vitro in chicken skin and in vivo in human subjects. The enthalpy change for the reaction determined by the van't Hoff plot was delta H degree = -21.58 kJ mol-1 in human skin and delta H degree = -15.60 kJ mol-1 in hexane. Arrhenius plots showed that the activation energies for both the forward and the reverse reactions were lower in human skin (Ea1 = 71.05 kJ mol-1 and Ea2 = 92.63 kJ mol-1) than in hexane (Ea1 = 84.90 kJ mol-1 and Ea2 = 100.5 kJ mol-1). Activation parameters for the reaction in human skin and in hexane were also reported. Subcellular fractionation of human epidermal tissue revealed that most epidermal 7-dehydrocholesterol and previtamin D3 were in the membrane fraction, while only 20% were in the cytosol. The interaction of previtamin D3 with intracellular lipids and/or proteins in skin may be responsible for the increased vitamin D3 formation rate in the skin.