The mechanism of oxythiamine-induced collagen biosynthesis in cultured fibroblasts

HMGA1 promotes the progression of esophageal squamous cell carcinoma by elevating TKT-mediated upregulation of pentose phosphate pathway

Esophageal squamous cell carcinoma (ESCC) possesses a poor prognosis and treatment outcome. Dysregulated metabolism contributes to unrestricted growth of multiple cancers. However, abnormal metabolism, such as highly activated pentose phosphate pathway (PPP) in the progression of ESCC remains largely unknown. Herein, we report that high-mobility group AT-hook 1 (HMGA1), a structural transcriptional factor involved in chromatin remodeling, promoted the development of ESCC by upregulating the PPP. We found that HMGA1 was highly expressed in ESCC. Elevated HMGA1 promoted the malignant phenotype of ESCC cells. Conditional knockout of HMGA1 markedly reduced 4-nitroquinoline-1-oxide (4NQO)-induced esophageal tumorigenesis in mice. Through the metabolomic analysis and the validation assay, we found that HMGA1 upregulated the non-oxidative PPP. With the transcriptome sequencing, we identified that HMGA1 upregulated the expression of transketolase (TKT), which catalyzes the reversible reaction in non-oxidative PPP to exchange metabolites with glycolytic pathway. HMGA1 knockdown suppressed the PPP by downregulating TKT, resulting in the reduction of nucleotides in ESCC cells. Overexpression of HMGA1 upregulated PPP and promoted the survival of ESCC cells by activating TKT. We further characterized that HMGA1 promoted the transcription of TKT by interacting with and enhancing the binding of transcription factor SP1 to the promoter of TKT. Therapeutics targeting TKT with an inhibitor, oxythiamine, reduced HMGA1-induced ESCC cell proliferation and tumor growth. Together, in this study, we identified a new role of HMGA1 in ESCCs by upregulating TKT-mediated activation of PPP. Our results provided a new insight into the role of HMGA1/TKT/PPP in ESCC tumorigenesis and targeted therapy.

In Vitro and In Silico Studies on Cytotoxic Properties of Oxythiamine and 2'-Methylthiamine

It is important to search for cytostatic compounds in order to fight cancer. One of them could be 2'-methylthiamine, which is a thiamine antimetabolite with an additional methyl group at the C-2 carbon of thiazole. So far, the cytostatic potential of 2'-methylthiamine has not been studied. We have come forward with a simplified method of synthesis using commercially available substrates and presented a comparison of its effects, as boosted by oxythiamine, on normal skin fibroblasts and HeLa cancer cells, having adopted in vitro culture techniques. Oxythiamine has been found to inhibit the growth and metabolism of cancer cells significantly better than 2'-methylthiamine (GI50 36 and 107 µM, respectively), while 2'-methylthiamine is more selective for cancer cells than oxythiamine (SI = 180 and 153, respectively). Docking analyses have revealed that 2'-methylthiamine (ΔG -8.2 kcal/mol) demonstrates a better affinity with thiamine pyrophosphokinase than thiamine (ΔG -7.5 kcal/mol ) and oxythiamine (ΔG -7.0 kcal/mol), which includes 2'-methylthiamine as a potential cytostatic. Our results suggest that the limited effect of 2'-methylthiamine on HeLa arises from the related arduous transport as compared to oxythiamine. Given that 2'-methylthiamine may possibly inhibit thiamine pyrophosphokinase, it could once again be considered a potential cytostatic. Thus, research should be carried out in order to find the best way to improve the transport of 2'-methylthiamine into cells, which may trigger its cytostatic properties.

Deciphering the underlying wound healing mechanisms of Streptocaulon juventas (Lour.) Merr. by integrating network pharmacology, transcriptomics, and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Streptocaulon juventas (Lour.) Merr. (SJ), a traditional Chinese folk medicine, has been widely used for the treatment of dysentery and traumatic injuries since ancient times. However, the mechanisms underlying its wound healing activity remain unclear.

AIM OF THE STUDY

The aim of this study was to evaluate the wound healing activity of SJ and clarify the underlying molecular mechanisms.

MATERIALS AND METHODS

The wound healing activity of an ethanol extract of SJ (ESJ) was confirmed in rat full-thickness wound models. UPLC-Q-TOF-MS/MS was used to analyze the composition of ESJ. Potential molecular targets and signaling pathways involved in the wound healing activity of ESJ were predicted using network pharmacology and transcriptomic analyses. In addition, the L929 cells were used to evaluate the in vitro wound healing activity of ESJ and to verify the predicted pathways.

RESULTS

In rat wound models, ESJ significantly accelerated wound healing and promoted hydroxyproline production in wounds. Network pharmacology and transcriptomic analyses results revealed that ESJ might promote wound healing by activating the AKT and MAPK pathways. In L929 cells, ESJ significantly promoted cell proliferation, migration, and expression of collagen I and α-SMA. Additionally, ESJ treatment increased the phosphorylation of AKT, mTOR, ERK, and p38 in a time- and dose-dependent manner.

CONCLUSIONS

ESJ significantly promoted wound healing in vivo and in vitro. AKT-mTOR and ERK-p38 signaling pathways were involved in the wound healing activity of ESJ.

Cell energy metabolism and bone formation

Energy metabolism plays an important role in cell and tissue ability to effectively function, maintain homeostasis, and perform repair. Yet, the role of energy metabolism in skeletal tissues in general and in bone, in particular, remains understudied. We, here, review the aspects of cell energy metabolism relevant to bone tissue, such as: i) availability of substrates and oxygen; ii) metabolism regulatory mechanisms most active in bone tissue, e.g. HIF and BMP; iii) crosstalk of cell bioenergetics with other cell functions, e.g. proliferation and differentiation; iv) role of glycolysis and mitochondrial oxidative phosphorylation in osteogenic lineage; and v) most significant changes in bone energy metabolism observed in aging and other pathologies. In addition, we review available methods to study energy metabolism on a subcellular, cellular, tissue, and live animal levels.

Differences in the efficiency of 3-deazathiamine and oxythiamine pyrophosphates as inhibitors of pyruvate dehydrogenase complex and growth of HeLa cells in vitro

Oxythiamine (OT) and 3-deazathiamine (DAT) are the antimetabolites of thiamine. The aim of study was to compare the effects of OT and DAT pyrophosphates (-PP) on the kinetics of mammalian pyruvate dehydrogenase complex (PDHC) and the in vitro culture of HeLa cells. The kinetic study showed that 3-deazathiamine pyrophosphate (DATPP) was a much stronger competitive inhibitor (K_i = 0.0026 μM) of PDHC than OTPP (K_i = 0.025 μM). Both K_i values were much lower versus K_m for thiamine pyrophosphate (0.06 μM). However, DATPP added to the culture medium for the HeLa cells culture did not hamper the rate of cell growth and showed not significant impact on the viability of the cells, whereas OTPP and OT showed a significant cytostatic effect. The differences between the thiamine antivitamins in their effect on cell growth in vitro may be due to differences in physicochemical properties and difficulty in DAT transport across the cell membrane.

The phosphoenolpyruvate carboxykinase (PEPCK) inhibitor, 3-mercaptopicolinic acid (3-MPA), induces myogenic differentiation in C2C12 cells

Phosphoenolpyruvate carboxykinase (PEPCK) is a gluconeogenic enzyme with a cytosolic (Pck1/PEPCK-C) and mitochondrial (Pck2/PEPCK-M) isoform. Here we investigate the effect of 3-mercaptopicolinic acid (3-MPA), a PEPCK inhibitor, on C2C12 muscle cells. We report that Pck2 mRNA is 50–5000-fold higher than Pck1 during C2C12 myogenesis, indicating Pck2 is the predominant PEPCK isoform. C2C12 cell proliferation was inhibited in a dose-dependent manner following 48 h 3-MPA treatment (0.01–1 mM). C2C12 myogenic differentiation was significantly induced following 3-MPA treatment (0.25, 0.5, 1 mM) from day 0 of differentiation, demonstrated by increased creatine kinase activity, fusion index and myotube diameter; likewise, the myosin heavy chain (MyHC)-IIB isoform (encoded by Myh4) is an indicator of hypertrophy, and both porcine MYH4-promoter activity and endogenous Myh4 mRNA were also significantly induced. High doses (0.5 and/or 1 mM) of 3-MPA reduced mRNA expression of Pck2 and genes associated with serine biosynthesis (Phosphoglycerate dehydrogenase, Phgdh; phosphoserine aminotransferase-1, Psat1) following treatment from days 0 and 4. To conclude, as Pck2/PEPCK-M is the predominant isoform in C2C12 cells, we postulate that 3-MPA promoted myogenic differentiation through the inhibition of PEPCK-M. However, we were unable to confirm that 3-MPA inhibited PEPCK-M enzyme activity as 3-MPA interfered with the PEPCK enzyme assay, particularly at 0.5 and 1 mM.

Proline-dependent regulation of collagen metabolism

This review is focused on recent data on the role of proline (Pro) in collagen biosynthesis and cellular metabolism. It seems obvious that one of the main substrates for collagen biosynthesis Pro is required to form collagen molecule. The question raised in this review is whether the Pro for collagen biosynthesis is synthesized "de novo", comes directly from degraded proteins or it is converted from other amino acids. Recent data provided evidence that extracellular Pro (added to culture medium) had significant, but relatively little impact on collagen biosynthesis in fibroblasts (the main collagen synthesized cells) cultured in the presence of glutamine (Gln). However, extracellular Pro drastically increased collagen biosynthesis in the cells cultured in Gln-free medium. It suggests that Pro availability determines the rate of collagen biosynthesis and demand for Pro in fibroblasts is predominantly met by conversion from Gln. The potential mechanism of this process as well as possible implication of this knowledge in pharmacotherapy of connective tissue diseases is discussed in this review.

Thiamine and selected thiamine antivitamins - biological activity and methods of synthesis

Thiamine plays a very important coenzymatic and non-coenzymatic role in the regulation of basic metabolism. Thiamine diphosphate is a coenzyme of many enzymes, most of which occur in prokaryotes. Pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes as well as transketolase are the examples of thiamine-dependent enzymes present in eukaryotes, including human. Therefore, thiamine is considered as drug or diet supplement which can support the treatment of many pathologies including neurodegenerative and vascular system diseases. On the other hand, thiamine antivitamins, which can interact with thiamine-dependent enzymes impeding their native functions, thiamine transport into the cells or a thiamine diphosphate synthesis, are good propose to drug design. The development of organic chemistry in the last century allowed the synthesis of various thiamine antimetabolites such as amprolium, pyrithiamine, oxythiamine, or 3-deazathiamine. Results of biochemical and theoretical chemistry research show that affinity to thiamine diphosphate-dependent enzymes of these synthetic molecules exceeds the affinity of native coenzyme. Therefore, some of them have already been used in the treatment of coccidiosis (amprolium), other are extensively studied as cytostatics in the treatment of cancer or fungal infections (oxythiamine and pyrithiamine). This review summarizes the current knowledge concerning the synthesis and mechanisms of action of selected thiamine antivitamins and indicates the potential of their practical use.

Panax ginseng total protein promotes proliferation and secretion of collagen in NIH/3T3 cells by activating extracellular signal-related kinase pathway

BACKGROUND

Recently, protein from ginseng was studied and used for the treatment of several kinds of diseases. However, the effect of ginseng total protein (GTP) on proliferation and wound healing in fibroblast cells remains unclear.

METHODS

In this study, cell viability was analyzed using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Cell cycle distribution was analyzed by flow cytometer. The levels of transforming growth factor β1, vascular endothelial growth factor, and collagens were analyzed by enzyme-linked immunosorbent assay and immunofluorescence staining. The expressions of cyclin A, phosphorylation of extracellular signal-related kinase (p-ERK1/2), and ERK1/2 were analyzed by Western blotting.

RESULTS

Our results showed that GTP promoted cell proliferation and increased the percentage of cells in S phase through the upregulation of cyclin A in NIH/3T3 cells. We also found that GTP induced the secretion of type I collagen, and promoted the expression of other factors that regulate the synthesis of collagen such as transforming growth factor β1 and vascular endothelial growth factor. In addition, the phosphorylation of ERK1/2 at Thr202/Tyr204 was also increased by GTP.

CONCLUSION

Our studies suggest that GTP promoted proliferation and secretion of collagen in NIH/3T3 cells by activating the ERK signal pathway, which shed light on a potential function of GTP in promoting wound healing.

Prolidase-proline dehydrogenase/proline oxidase-collagen biosynthesis axis as a potential interface of apoptosis/autophagy

Prolidase is a cytosolic imidodipeptidase that specifically splits imidodipeptides with C-terminal proline or hydroxyproline. The enzyme plays an important role in the recycling of proline from imidodipeptides for resynthesis of collagen and other proline-containing proteins. The mechanism of prolidase-dependent regulation of collagen biosynthesis was found at both transcriptional and post-transcriptional level. The increase in the enzyme activity is due to its phosphorylation on serine/threonine residues. Prolidase-dependent transcriptional regulation of collagen biosynthesis was found at the level of NF-κB, known inhibitor of type I collagen gene expression. Proline dehydrogenase/proline oxidase (PRODH/POX) is flavin-dependent enzyme associated with the inner mitochondrial membrane. The enzyme catalyzes conversion of proline into Δ(1) -pyrroline-5-carboxylate (P5C), during which reactive oxygen species (ROS) are produced, inducing intrinsic and extrinsic apoptotic pathways. Alternatively, under low glucose stress, PRODH/POX activation produces ATP for energy supply and survival. Of special interest is that PRODH/POX gene is induced by P53 and peroxisome proliferator-activated gamma receptor (PPARγ). Among down-regulators of PRODH/POX is an oncogenic transcription factor c-MYC and miR-23b*. On the other hand, PRODH/POX suppresses HIF-1α transcriptional activity, the MAPK pathway, cyclooxygenase-2, epidermal growth factor receptor and Wnt/b-catenin signaling. PRODH/POX expression is often down-regulated in various tumors, limiting mitochondrial proline utilization to P5C. It is accompanied by increased cytoplasmic level of proline. Proline availability for PRODH/POX-dependent ATP or ROS generation depends on activity of prolidase and utilization of proline in process of collagen biosynthesis. Therefore, Prolidase-PRODH/POX-Collagen Biosynthesis axis may represent potential interface that regulate apoptosis and survival. © 2016 BioFactors, 42(4):341-348, 2016.

Thiamine antivitamins--an opportunity of therapy of fungal infections caused by Malassezia pachydermatis and Candida albicans

Severe skin diseases and systemic fungaemia are caused by Malassezia pachydermatis and Candida albicans respectively. Antifungal therapies are less effective because of chronic character of infections and high percentage of relapses. Therefore, there is a great need to develop new strategies of antifungal therapies. We previously found that oxythiamine decreases proliferation of yeast (Saccharomyces cerevisiae), therefore we suggest that thiamine antivitamins can be considered as antifungal agents. The aim of this study was the comparison of thiamine antivitamins (oxythiamine, amprolium, thiochrome, tetrahydrothiamine and tetrahydrooxythiamine) inhibitory effect on the growth rate and energetic metabolism efficiency in non-pathogenic S. cerevisiae and two potentially pathogenic species M. pachydermatis and C. albicans. Investigated species were cultured on a Sabouraud medium supplemented with trace elements in the presence (40 mg l(-1)) or absence of each tested antivitamins to estimate their influence on growth rate, enzyme activity and kinetic parameters of pyruvate decarboxylase and malate dehydrogenase of each tested species. Oxythiamine was the only antivitamin with antifungal potential. M. pachydermatis and S. cerevisiae were the most sensitive, whereas C. albicans was the least sensitive to oxythiamine action. Oxythiamine can be considered as supportive agent in superficial mycoses treatment, especially those caused by species from the genus Malassezia.