Programmed cell death of stressed keratinocytes and its inhibition by vitamin D: The role of death and survival signaling pathways

Quantitative proteomic and metabolomic profiling reveals different osmoregulation mechanisms of tilapia cells coping with different hyperosmotic stress

This study aimed to investigate the different regulatory mechanisms of euryhaline fish under regular hyperosmotic and extreme hyperosmotic stress. The OmB (Oreochromis mossambicus brain) cells were exposed to three treatments: control, regular hyperosmotic stress and extreme hyperosmotic stress. After 12 h exposure, proteomics, metabolomics analyses and integrative analyses were explored. Both kinds of stress lead to lowering cell growth and morphology changes, while under regular hyperosmotic stress, the up-regulated processes related with compatible organic osmolytes synthesis are crucial strategy for the euryhaline fish cell line to survive; On the other hand, under extreme hyperosmotic stress, the processes related with cell apoptosis and cell cycle arrest are dominant. Furthermore, down-regulated pyrimidine metabolism and several ribosomal proteins partially participated in the lowered cell metabolism and increased cell death under both kinds of hyperosmotic stress. The PI3K-Akt and p53 signaling pathways were involved in the stagnant stage of cell cycles and induction of cell apoptosis under both kinds of hyperosmotic stress. However, HIF-1, FoxO, JAK-STAT and Hippo signaling pathways mainly contribute to disrupting the cell cycle, metabolism and induction of cell apoptosis under extreme hyperosmotic stress. SIGNIFICANCE: In the past, the research on fish osmoregulation mainly focused on the transcription factors and ion transporters of osmoregulation, the processes between osmotic sensing and signal transduction, and the associations between signaling pathways and regulation processes have been poorly understood. Investigating fish cell osmoregulation and potential signal transduction pathways is necessary. With the advancements in omics research, it is now feasible to investigate the relationship between environmental stress and molecular responses. In this study, we aimed to explore the signaling pathways and substance metabolism mode during hyper-osmoregulation in OmB cell line, to reveal the key factors that are critical to cell osmoregulation.

Vitamin D and Ocular Diseases: A Systematic Review

The contributory roles of vitamin D in ocular and visual health have long been discussed, with numerous studies pointing to the adverse effects of vitamin D deficiency. In this paper, we provide a systematic review of recent findings on the association between vitamin D and different ocular diseases, including myopia, age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), dry eye syndrome (DES), thyroid eye disease (TED), uveitis, retinoblastoma (RB), cataract, and others, from epidemiological, clinical and basic studies, and briefly discuss vitamin D metabolism in the eye. We searched two research databases for articles examining the association between vitamin D deficiency and different ocular diseases. One hundred and sixty-two studies were found. There is evidence on the association between vitamin D and myopia, AMD, DR, and DES. Overall, 17 out of 27 studies reported an association between vitamin D and AMD, while 48 out of 54 studies reported that vitamin D was associated with DR, and 25 out of 27 studies reported an association between vitamin D and DES. However, the available evidence for the association with other ocular diseases, such as glaucoma, TED, and RB, remains limited.

NUTRITION AND BULLOUS DISEASES

Although relatively uncommon, autoimmune bullous diseases carry the risk of increased mortality and can significantly impact quality of life. This group of diseases is broad and encompasses subepidermal conditions like bullous pemphigoid, cicatricial pemphigoid, epidermolysis bullosa acquisita, dermatitis herpetiformis, and linear IgA bullous dermatosis, as well as intraepidermal conditions like pemphigus and its variants. The pathophysiology of each condition is incompletely understood but broadly involves the formation of autoantibodies targeting skin adhesion proteins, a process which relies on a complex interplay between a dysregulated immune system, genetic predisposition, and environmental factors. We review the impact of nutrition on pathogenesis, clinical course, and treatment of various autoimmune bullous diseases.

Vitamin D and Age-Related Macular Degeneration

In recent years, the relationship between vitamin D and health has received growing attention from the scientific and medical communities. Vitamin D deficiencies have been repeatedly associated with various acute and chronic diseases, including age-related macular degeneration (AMD). Its active metabolite, 1α,25-dihydoxy vitamin D, acts as a modulator of cell proliferation, differentiation and apoptosis, and cumulative data from experimental and observational studies suggest that relatively a lower vitamin D status could be a potential risk factor for the development of early and/or late AMD. Herein, we made a narrative review of the mechanisms linking a potential role of vitamin D with the current concepts of AMD pathophysiology.

Role of macrophage migration inhibitory factor in heat-induced apoptosis in keratinocytes

In human skin, keratinocytes are constantly challenged by adverse influences, such as hot and cold temperatures; however, the effects of heat on apoptosis induction in keratinocytes are not well understood. Macrophage migration inhibitory factor (MIF) is a potent cytokine that overcomes p53 function by suppressing its transcriptional activity. Here, we evaluated the effects of MIF on hyperthermia (HT)-induced apoptosis in MIF-deficient [knockout (KO)] and MIF-transgenic (Tg) mouse keratinocytes. Cells were exposed to HT at 44°C, and increased apoptosis was observed in MIF-KO and wild-type (WT) cells compared with MIF-Tg cells. To determine the mechanism, MIF-mediated changes in the cellular p53 level and its effects on p53-dependent death signaling (Bax and p21) and JNK signaling (p-JNK, JNK, p-Bad, and Bad) were investigated. MIF-Tg cells exhibited substantially decreased levels of p53 after HT treatment compared with WT and MIF-KO cells. In addition, HT treatment caused decreased expression of p-JNK and p-Bad in MIF-Tg cells; however, no such changes were observed in MIF-KO and WT cells. These results showed that the activation of JNK (p-JNK and p-Bad) and p53 may be involved in HT-induced apoptosis in keratinocytes and that enhanced endogenous MIF expression suppressed apoptosis.-Yoshihisa, Y., Rehman, M. U., Kondo, T., Shimizu, T. Role of macrophage migration inhibitory factor in heat-induced apoptosis in keratinocytes.

Vitamin D derivatives enhance cytotoxic effects of H2O2 or cisplatin on human keratinocytes

Although the skin production of vitamin D is initiated by ultraviolet radiation type B (UVB), the role vitamin D plays in antioxidative or pro-oxidative responses remains to be elucidated. We have used immortalized human HaCaT keratinocytes as a model of proliferating epidermal cells to test the influence of vitamin D on cellular response to H2O2 or the anti-cancer drug, cisplatin. Incubation of keratinocytes with 1,25(OH)2D3 or its low calcemic analogues, 20(OH)D3, 21(OH)pD or calcipotriol, sensitized cells to ROS resulting in more potent inhibition of keratinocyte proliferation by H2O2 in the presence of vitamin D compounds. These results were supported by cell cycle and apoptosis analyses, and measurement of the mitochondrial transmembrane potentials (MMP), however some unique properties of individual secosteroids were observed. Furthermore, in HaCaT keratinocytes treated with H2O2, 1,25(OH)2D3, 21(OH)pD and calcipotriol stimulated the expression of SOD1 and CAT genes, but not SOD2, indicating a possible role of mitochondria in ROS-modulated cell death. 1,25(OH)2D3 also showed a short-term, protective effect on HaCaT keratinocytes, as exemplified by the inhibition of apoptosis and the maintenance of MMP. However, with prolonged incubation with H2O2 or cisplatin, 1,25(OH)2D3 caused an acceleration in the death of the keratinocytes. Therefore, we propose that lead vitamin D derivatives can protect the epidermis against neoplastic transformation secondary to oxidative or UV-induced stress through activation of vitamin D-signaling. Furthermore, our data suggest that treatment with low calcemic vitamin D analogues or the maintenance of optimal level of vitamin D by proper supplementation, can enhance the anticancer efficacy of cisplatin.

TNF-α increases the expression and activity of vitamin D receptor in keratinocytes: role of c-Jun N-terminal kinase

Several inflammatory mediators increase calcitriol production by epidermal keratinocytes. In turn calcitriol attenuates the keratinocyte inflammatory response. Since the effect of the in-situ generated calcitriol depends also on the sensitivity to the hormone we studied the effect of inflammatory cytokines on the response of HaCaT human keratinocytes to calcitriol by examining the expression and transcriptional activity of VDR. Treatment with TNF, but not with IL-1β or interferon γ, increased VDR protein level, while decreasing the level of its heterodimerization partner RXRα. This was associated with increased VDR mRNA levels. c-Jun N-terminal kinase, but not P38 MAPK or NFκB, was found to participate in the upregulation of VDR by TNF. The functional significance of the modulation of VDR and RXRα levels by TNF is manifested by increased induction of VDR target gene CYP24A1 by calcitriol. Calcitriol, in turn, inhibited the enhanced expression of VDR by TNF. In conclusion, the inflammatory cytokine TNF increases the response of keratinocytes to calcitriol through upregulation of its receptor VDR, which in turn is subject to negative feedback by the hormone accelerating the return of the keratinocyte vitamin D system to its basal activity. We surmise that the increased generation and sensitivity to calcitriol in keratinocytes play a role in the resolution of epidermal inflammation.

Vitamin D Induces Cyclooxygenase 2 Dependent Prostaglandin E2 Synthesis in HaCaT Keratinocytes

The active metabolite of vitamin D calcitriol and its analogs are well-known for their anti-inflammatory action in the skin, while their main side effect associated with topical treatment of inflammatory disorders is irritant contact dermatitis. Prostaglandin E2 (PGE2 ) is pro-inflammatory at the onset of inflammation and anti-inflammatory at its resolution. We hypothesized that induction of PGE2 synthesis by calcitriol in epidermal keratinocytes may contribute both to its pro-inflammatory and anti-inflammatory effects on the skin. Treatment of human immortalized HaCaT keratinocytes with calcitriol (3-100 nM, 2-24 h) increased PGE2 production due to increased mRNA and protein expression of COX-2, but not to increase of COX-1 or release of arachidonic acid. The effect of calcitriol on COX-2 mRNA was observed also in primary human keratinocytes. The increase in COX-2 mRNA is associated with COX-2 transcript stabilization. Calcitriol exerts this effect by a rapid (2 h) and protein synthesis independent mode of action that is dependent on PKC and Src kinase activities. Treatment with a COX-2 inhibitor partially prevented the attenuation of the keratinocyte inflammatory response by calcitriol. We conclude that upregulation of COX-2 expression with the consequent increase in PGE2 synthesis may be one of the mechanisms explaining the Janus face of calcitriol as both a promoter and attenuator of cutaneous inflammation. J. Cell. Physiol. 231: 837-843, 2016. © 2015 Wiley Periodicals, Inc.

Activation of the low molecular weight protein tyrosine phosphatase in keratinocytes exposed to hyperosmotic stress

Herein, we provide new contribution to the mechanisms involved in keratinocytes response to hyperosmotic shock showing, for the first time, the participation of Low Molecular Weight Protein Tyrosine Phosphatase (LMWPTP) activity in this event. We reported that sorbitol-induced osmotic stress mediates alterations in the phosphorylation of pivotal cytoskeletal proteins, particularly Src and cofilin. Furthermore, an increase in the expression of the phosphorylated form of LMWPTP, which was followed by an augment in its catalytic activity, was observed. Of particular importance, these responses occurred in an intracellular milieu characterized by elevated levels of reduced glutathione (GSH) and increased expression of the antioxidant enzymes glutathione peroxidase and glutathione reductase. Altogether, our results suggest that hyperosmostic stress provides a favorable cellular environment to the activation of LMWPTP, which is associated with increased expression of antioxidant enzymes, high levels of GSH and inhibition of Src kinase. Finally, the real contribution of LMWPTP in the hyperosmotic stress response of keratinocytes was demonstrated through analysis of the effects of ACP1 gene knockdown in stressed and non-stressed cells. LMWPTP knockdown attenuates the effects of sorbitol induced-stress in HaCaT cells, mainly in the status of Src kinase, Rac and STAT5 phosphorylation and activity. These results describe for the first time the participation of LMWPTP in the dynamics of cytoskeleton rearrangement during exposure of human keratinocytes to hyperosmotic shock, which may contribute to cell death.

Estimation of vitamin D levels in patients with pemphigus vulgaris

BACKGROUND

Keratinocyte acantholysis as a result of pathogenic Dsg3-antibodies production by B cells leads to Pemphigus vulgaris (PV). Vitamin D, through its participation in several immune modulatory functions including B cells apoptosis, Th2 cell differentiation, apoptotic enzyme regulation and Tregs functions, may be actively involved in the immune regulation of PV.

OBJECTIVE

To evaluate Vitamin D status in PV patients in comparison to controls in an attempt to determine its role in this autoimmune disease.

METHODS

Using ELISA technique, 25-hydroxyvitamin D (25OHD) was determined for 34 pemphigus vulgaris patients and 20 healthy volunteers. Phosphorus and parathormone were also determined in the patient group.

RESULTS

25OHD was significantly lower in patients than controls (P = 0.008). There was a statistically significant difference between both groups regarding suboptimal Vit. D levels (P = 0.007).

CONCLUSION

Patients with PV have significantly lower serum vitamin D levels in comparison to controls and that these low levels were not related to age, BMI or pattern of sun exposure. The associated Vitamin D insufficiency in patients with PV may possibly exacerbate their disease through various immune related mechanisms.

Vitamin D and death by sunshine

Exposure to sunlight is the major cause of skin cancer. Ultraviolet radiation (UV) from the sun causes damage to DNA by direct absorption and can cause skin cell death. UV also causes production of reactive oxygen species that may interact with DNA to indirectly cause oxidative DNA damage. UV increases accumulation of p53 in skin cells, which upregulates repair genes but promotes death of irreparably damaged cells. A benefit of sunlight is vitamin D, which is formed following exposure of 7-dehydrocholesterol in skin cells to UV. The relatively inert vitamin D is metabolized to various biologically active compounds, including 1,25-dihydroxyvitamin D3. Therapeutic use of vitamin D compounds has proven beneficial in several cancer types, but more recently these compounds have been shown to prevent UV-induced cell death and DNA damage in human skin cells. Here, we discuss the effects of vitamin D compounds in skin cells that have been exposed to UV. Specifically, we examine the various signaling pathways involved in the vitamin D-induced protection of skin cells from UV.

The inflammatory response of keratinocytes and its modulation by vitamin D: the role of MAPK signaling pathways

The hormonal form of vitamin D, calcitriol, and its analogs are known for their beneficial effect in the treatment of inflammatory skin disorders. Keratinocytes play a role in epidermal inflammatory responses invoked by breeching of the epidermal barrier, by infectious agents and by infiltrating immune cells. We studied the role of calcitriol in the initiation of keratinocyte inflammatory response by the viral and injury mimic polyinosinic-polycytidylic acid (poly(I:C)) and in its maintenance by tumor-necrosis-factor α (TNFα) and investigated the role of the mitogen-activated protein kinase cascades in these processes and their regulation by calcitriol. The inflammatory response of human HaCaT keratinocytes to poly(I:C) or TNFα was assessed by measuring mRNA levels of 13 inflammation-related molecules by real-time PCR microarray and by in-depth investigation of the regulation of interleukin 8, intercellular-adhesion-molecule 1, and TNFα expression. We found that while calcitriol had only a minor effect on the keratinocyte response to poly(I:C) and a modest effect on the early response (2 h) to TNFα, it markedly attenuated the later response (16-24 h) to TNFα. The expression of CYP27B1, the enzyme responsible for calcitriol production, was marginally increased by poly(I:C) and markedly by TNFα treatment. This pattern suggests that while allowing the initial keratinocyte inflammatory response to proceed, calcitriol contributes to its timely resolution. Using pharmacological inhibitors we found that while the p38 MAPK and the extracellular signal-regulated kinase have only a minor role, c-Jun N-terminal kinase plays a pivotal role in the induction of the pro-inflammatory genes and its modulation by calcitriol.

Podocytopathy in diabetes: a metabolic and endocrine disorder

Diabetic nephropathy (DN) represents a major public health cost. Tight glycemic and blood pressure control can dramatically slow, but not stop, the progression of the disease, and a large number of patients progress toward end-stage renal disease despite currently available interventions. An early and key event in the development of DN is loss of podocyte function (or glomerular visceral epithelial cells) from the kidney glomerulus, where they contribute to the integrity of the glomerular filtration barrier. Recent evidence suggests that podocytes can be the direct target of circulating hormones, lipids, and adipokines that are affected in diabetes. We review the clinical and experimental evidence implicating novel endocrine and metabolic pathways in the pathogenesis of podocyte dysfunction and the development of DN.

Vitamin D inhibits captopril-induced cell detachment and apoptosis in keratinocytes

BACKGROUND

Captopril, an angiotensin I-converting enzyme inhibitor, is a commonly prescribed antihypertensive drug. Its cutaneous side-effects include pemphigus vulgaris acantholysis and bullous pemphigoid-like cell-matrix detachment. This medication also triggers apoptosis in human keratinocytes. Calcitriol, the hormonally active vitamin D metabolite, protects keratinocytes from programmed cell death induced by various noxious stimuli.

OBJECTIVES

To examine if calcitriol protects proliferating keratinocytes from the damage inflicted by captopril.

METHODS

Autonomously proliferating HaCaT keratinocytes, used as a model for basal layer keratinocytes, were exposed to captopril. Cell detachment was examined visually by light microscopy. Cytotoxicity was assessed by Hoechst 33342 staining and lactate dehydrogenase release. Apoptotic death was assessed by monitoring caspase 3-like activity.

RESULTS

Cells exposed to captopril detached and became round. This process was accompanied by programmed cell death. From time-dependent monitoring of cell detachment and apoptosis, and examination of pan-caspase inhibitor effects on cell detachment we concluded that cell death is the consequence of cell detachment from the culture plate and not vice versa. Pretreatment with calcitriol significantly attenuated these events. The effects of calcitriol were already evident at 1 nmol L(-1) concentration of the hormone.

CONCLUSIONS

The results of this study show that calcitriol protects keratinocytes from captopril-induced cell detachment and apoptosis.

Keratinocyte growth factor protected cultured human keratinocytes exposed to oxidative stress

PURPOSE

To evaluate effects of oxidative stress and supplementation of keratinocyte growth factor (KGF) on cultivated human keratinocytes.

METHODS

Oxidative stress was produced through addition of hydrogen peroxide (H(2)O(2)) to the culture medium. Cultivated human keratinocytes were divided in 4 groups: Group control (G C), Group KGF (G KGF), Group H(2)O(2) (G H(2)O(2)), Group H(2)O(2) and KGF (G H(2)O(2)-KGF). Each experiment was accomplished with the same lineage cultivated keratinocytes, in triplicate. Cell viability was evaluated by trypan blue exclusion assay.

RESULTS

The results showed that the culture medium supplemented with KGF presented a small rate of cell viability when compared to cells only in culture medium (p<0,001). It demonstrated that only the growth factor does not have protector effects for cells in vitro. However, in front of the oxidative stress produced by addition of hydrogen peroxide to the medium, KGF showed a beneficial effect, protecting cells when compared to the group that suffered hydrogen peroxide action but had not been exposed to KGF (p<0,001).

CONCLUSION

KGF determined protection to the primary human keratinocytes exposed to oxidative stress.

Protection against cellular stress by 25-hydroxyvitamin D3 in breast epithelial cells

25-Hydroxyvitamin D(3) (25(OH)D(3)) is a prohormone and a major vitamin D metabolite. The discovery of (25(OH)D(3)) 1 alpha-hydroxylase in many vitamin D target organs has yielded an increased interest in defining the role(s) of 25(OH)D(3) in these tissues. The etiology of cancer appears to be complex and multi-factorial. Cellular stress (e.g., DNA damage, hypoxia, oncogene activation) has been identified as one of the key factors responsible for initiating the carcinogenesis process. In this study, we investigated whether 25(OH)D(3) protects breast epithelial cells from cellular stress using an established breast epithelial cell line MCF12F. To better elucidate the role of 25(OH)D(3) in the stress response, we used multiple in vitro stress models including serum starvation, hypoxia, oxidative stress, and apoptosis induction. Under all these stress conditions, 25(OH)D(3) (250 nmol/L) treatment significantly protected cells against cell death. Low-serum stress induced p53 expression accompanied with downregulation of PCNA, the presence of 25(OH)D(3) consistently inhibited the alteration of p53 and PCNA, suggesting that these molecules were involved in the stress process and may be potential target genes of 25(OH)D(3). miRNA microarray analysis demonstrated that stress induced by serum starvation caused significant alteration in the expression of multiple miRNAs including miR182, but the presence of 25(OH)D(3) effectively reversed this alteration. These data suggest that there is a significant protective role for 25(OH)D(3) against cellular stress in the breast epithelial cells and these effects may be mediated by altered miRNA expression.

The impact of methylmercury on 1,25-dihydroxyvitamin D3-induced transcriptomic responses in dolphin skin cells

The Atlantic bottlenose dolphin has been the focus of much attention owing to the considerable impact of environmental stress on its health and the associated implications for human health. Here, we used skin cells from the dolphin to investigate the protective role of the vitamin D pathway against environmental stressors. We previously reported that dolphin skin cells respond to 1,25-dihydroxyvitamin D3 (1,25D3), the bioactive metabolite of vitamin D3, by upregulation of the vitamin D receptor (VDR) and expression of several genes. Methylmercury is a highly bioaccumulative environmental stressor of relevance to the dolphin. We currently report that in dolphin cells sublethal concentrations of methylmercury compromise the ability of 1,25D3 to upregulate VDR, to transactivate a vitamin D-sensitive promoter, and to express specific target genes. These results help elucidate the effects of vitamin D and methylmercury on innate immunity in dolphin skin and potentially in human skin as well, considering similarities in the vitamin D pathway between the two species.

Upregulation of MMP-9 production by TNFalpha in keratinocytes and its attenuation by vitamin D

MMP-9, a member of the matrix metalloproteinase family that degrades collagen IV and processes chemokines and cytokines, participates in epidermal remodeling in response to stress and injury. Limited activity of MMP-9 is essential while excessive activity is deleterious to the healing process. Tumor necrosis factor (TNFalpha), a key mediator of cutaneous inflammation, is a powerful inducer of MMP-9. Calcitriol, the hormonally active vitamin D metabolite, and its analogs are known to attenuate epidermal inflammation. We aimed to examine the modulation of MMP-9 by calcitriol in TNFalpha-treated keratinocytes. The immortalized HaCaT keratinocytes were treated with TNFalpha in the absence of exogenous growth factors or active ingredients. MMP-9 production was quantified by gelatin zymography and real-time RT-PCR. Activation of signaling cascades was assessed by western blot analysis and DNA-binding activity of transcription factors was determined by EMSA. Exposure to TNFalpha markedly increased the protein and mRNA levels of MMP-9, while pretreatment with calcitriol dose dependently reduced this effect. Employing specific inhibitors we established that the induction of MMP-9 by TNFalpha was dependent on the activity of the epidermal growth factor receptor, c-Jun-N-terminal kinase (JNK), NFkappaB and extracellular signal-regulated kinase-1/2. The effect of calcitriol was associated with inhibition of JNK activation and reduction of DNA-binding activities of the transcription factors activator protein-1 (AP-1) and NFkappaB following treatment with TNFalpha. By down-regulating MMP-9 levels active vitamin D derivatives may attenuate deleterious effects due to excessive TNFalpha-induced proteolytic activity associated with cutaneous inflammation.

Vimentin phosphorylation as a target of cell signaling mechanisms induced by 1alpha,25-dihydroxyvitamin D3 in immature rat testes

The effects of 1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] are mainly mediated by nuclear receptors modulating gene expression. However, there are increasing evidences of nongenomic mechanisms of this hormone associated with kinase- and calcium-activated signaling pathways. In this context, the aim of the present work was to investigate the signaling pathways involved in the mechanism of action of 1,25(OH)(2)D(3) on vimentin phosphorylation in 15-day-old rat testes. Results showed that 1,25(OH)(2)D(3) at concentrations ranging from 1 nM to 1 microM increased vimentin phosphorylation independent of protein synthesis. We also demonstrated that the mechanisms underlying the hormone action involve protein kinase C activation in a phospholipase C-independent manner. Moreover, we showed that the participation of protein kinase A, extracellular regulated protein kinase (ERK), and intra- and extracellular Ca(2+) mediating the effects of 1,25(OH)(2)D(3) on the cytoskeleton. In addition, we investigated the effect of different times of exposure to the hormone on total and phosphoERK1/2 or c-Jun N-terminal kinases 1/2 (JNK1/2) in immature rat testis. Results showed that the total levels of ERK1/2 and JNK1/2 were unaltered from 1 to 15 min exposure to 1,25(OH)(2)D(3). However, the phosphoERK1/2 levels significantly increased at 1 and 5 min 1,25(OH)(2)D(3) treatment. Furthermore, phosphoJNK1 levels were decreased at 10 and 15 min 1,25(OH)(2)D(3) exposure, while phosphoJNK 2 levels were diminished at 5, 10 and 15 min treatment with the hormone. These findings demonstrate that 1,25(OH)(2)D(3) may modulate vimentin phosphorylation through nongenomic Ca(2+)-dependent mechanisms in testis cells.

Enamel matrix derivative protects human gingival fibroblasts from TNF-induced apoptosis by inhibiting caspase activation

Emdogain, a formulation of enamel matrix derivative (EMD), is used clinically for regeneration of the periodontium (tooth supporting tissues), but the molecular mechanisms of its action have not been elucidated. Several clinical studies suggested that EMD may also improve gingival healing after periodontal surgery and thus affect the fate of gingival fibroblasts (GFs). Since these cells are targets for local inflammatory mediators such as TNF, a pro-apoptotic cytokine, during the course of periodontal disease, we tested whether EMD protects human GFs (hGFs) from TNF-induced cytotoxicity. Quiescent primary hGFs were challenged with TNF (10-100 ng/ml) with or without EMD (100 microg/ml) pretreatment. Cell viability was assessed by neutral red staining, cell death by LDH release and apoptosis by caspase activity. Signaling pathways were evaluated by Western blotting and pharmacological inhibitors. TNF induced classical signs of apoptosis in hGFs, including typical cellular morphology and increased caspase activity. TNF-induced cytotoxicity was entirely caspase-dependent. Pretreatment (4-24 h) with EMD dramatically inhibited the activation of initiator and executioner caspases and enhanced hGF survival. Although TNF induced the activation of p38 MAPK, JNK, ERK and PI-3K signaling, these pathways were not crucial for EMD protection of hGFs. However, EMD increased the levels of c-FLIP(L), an anti-apoptotic protein located upstream of caspase activation. These data demonstrate, for the first time, that EMD protects hGFs from inflammatory cytokines and, together with our recent reports that EMD stimulates rat and human GF proliferation, could help explain the mechanisms whereby in vivo use of EMD promotes gingival healing.

A two-phase strategy for treatment of oxidant-dependent cancers

In many cancers, a chronic increase in oxidant stress - associated with elevated levels of hydrogen peroxide - contributes to the increased proliferative rate, diminished apoptosis, increased angiogenic and metastatic capacity, and chemoresistance that often characterize advanced malignancies. This oxidant stress often reflects up-regulation of expression and activity of NADPH oxidase, and/or decreased activity of catalase, which functions as suppressor gene in oxidant-dependent cancers. These characteristics of oxidant-dependent cancers suggest a dual strategy for treatment of these cancers. Since ascorbate can react spontaneously with molecular oxygen to generate hydrogen peroxide, high-dose intravenous ascorbate should be selectively toxic to tumors that are low in catalase activity - as suggested by numerous cell culture studies. Measures which concurrently improve the oxygenation of hypoxic tumor regions would be expected to boost the efficacy of such therapy; calcitriol and high-dose selenium might also be useful in this regard. Secondly, during the intervals between sessions of ascorbate therapy, administration of agents which can safely inhibit NADPH oxidase would be expected to slow the proliferation and spread of surviving tumor cells - while providing selection pressure for a further decline in catalase activity. In effect, cancers treated in this way would be whipsawed between lethally excessive and inadequately low oxidant stress. An additional possibility is that ascorbate-induced oxidant stress in tumors might potentiate the cell kill achieved with concurrently administered cytotoxic drugs, inasmuch as oxidant mechanisms appear to play a mediating role in the apoptosis induced by many such drugs, largely via activation of c-Jun NH(2)-terminal kinase; cell culture studies would be useful for evaluating this possibility.