Expression of TGF-betas and their receptors is differentially modulated by reactive oxygen species and nitric oxide in human articular chondrocytes

GDF15 enhances proliferation of aged chondrocytes by phosphorylating SMAD2

BACKGROUND

Aging is one of the primary factors influencing development of osteoarthritis, and the TGF-β pathway plays an important role in age-related osteoarthritis. Specifically, GDF15 phosphorylates SMAD2/3 in the TGF-β pathway to inhibit cardiomyocyte hypertrophy, and promote proliferation of chondrocytes. However, age-dependent changes in the level of GDF15 are unclear, as is whether GDF15 phosphorylates SMAD2/3 in the TGF-β pathway to promote proliferation of old chondrocytes. This study, therefore, sought to examine the effect of various GDF15 concentrations on old chondrocyte proliferation.

METHODS

Serum and cartilage specimens of young adults and older adults were collected, and GDF15 expression was quantified. Human chondrocytes were then cultured following routine protocols, and different concentrations of recombinant human GDF15 or pSMAD2 inhibitor were added into the culture medium. After 48 h of culturing, the proliferation of chondrocytes was detected by EdU, and the expression MMP13, SMAD2, and pSMAD2 was detected in chondrocytes via western blot and qRT-PCR analysis.

RESULTS

The GDF15 content in serum and cartilage of young adults was higher than that of older adults (p < 0.05). The number of EdU-positive cells in the experimental group (containing recombinant human GDF15) was higher than that in the control group (medium only) (p < 0.05). Compared with the control group, chondrocytes in the experimental group showed increased pSMAD2 and type II collagen content (p < 0.05) and decreased MMP13 (p < 0.05), with no significant difference in SMAD2 content (p > 0.05). Moreover, no significant differences were observed between the control group and the TGF-β signaling inhibitor group. The gene expression level of each index was consistent with the protein expression level.

CONCLUSIONS

The GDF15 content of serum and cartilage in young adults is higher than in older adults, and GDF15 functions to promote the proliferation of chondrocytes by phosphorylating SMAD2 in older individuals.

T-2 toxin induces articular cartilage damage by increasing the expression of MMP-13 via the TGF-β receptor pathway

T-2 toxin pre-disposes individuals to osteoarthritis, Kashin-Beck disease (KBD). The major pathological change associated with KBD is the degradation of the articular cartilage matrix. Herein, we investigated the key molecules that regulate T-2 toxin-mediated cartilage degradation. Potential KBD treatments were also investigated. Sprague Dawley rats were divided into the T-2 toxin group and the control group. The T-2 toxin group received 100 ng/g BW/day, whereas the control group received a similar dose of PBS. The expression of matrix metalloproteinase-13 (MMP-13) and TGF-β receptor I/II (TGF-βRI/II) was analyzed using immunohistochemical staining. C28/I2 chondrocytes were exposed to TGF-βRI/II binding inhibitor (GW788388) for 24 h before incubation in different T-2 toxin concentrations (0, 6, 12, and 24 ng/mL for 72 h). The expression of mRNA for TGF-βRI/II, MMP-13 and proteins for MMP-13, and Smad-2 in chondrocytes were analyzed using RT-PCR and western blot, respectively. Safranin O staining revealed that T-2 toxin treatment modulated the expression of articular cartilage matrix. On the other hand, T-2 toxin treatment sharply increased the expression of MMP-13, TGF-βRI, and TGF-βRII in the rat cartilages. Interestingly, blocking the TGF-βRs-smad 2 signaling pathway using GW788388 abrogated the effect of T-2 toxin on upregulating MMP-13 expression. The expression of MMP-13 in chondrocytes induced with T-2 toxin is regulated via the TGF-βRs signaling pathway. As such, inhibiting the expression of TGF-βRs is a potential KBD treatment.

ROS and TGFβ: from pancreatic tumour growth to metastasis

Transforming growth factor β (TGFβ) signalling pathway switches between anti-tumorigenic function at early stages of cancer formation and pro-tumorigenic effects at later stages promoting cancer metastasis. A similar contrasting role has been uncovered for reactive oxygen species (ROS) in pancreatic tumorigenesis. Down-regulation of ROS favours premalignant tumour development, while increasing ROS level in pancreatic ductal adenocarcinoma (PDAC) enhances metastasis. Given the functional resemblance, we propose that ROS-mediated processes converge with the spatial and temporal activation of TGFβ signalling and thereby differentially impact early tumour growth versus metastatic dissemination. TGFβ signalling and ROS could extensively orchestrate cellular processes and this concerted function can be utilized by cancer cells to facilitate their malignancy. In this article, we revisit the interplay of canonical and non-canonical TGFβ signalling with ROS throughout pancreatic tumorigenesis and metastasis. We also discuss recent insight that helps to understand their conflicting effects on different stages of tumour development. These considerations open new strategies in cancer therapeutics.

Lipopolysaccharide-induced expression of astrocyte elevated gene-1 promotes degeneration and inflammation of chondrocytes via activation of nuclear factor-κB signaling

Osteoarthritis is an inflammatory disease characterized by joint degeneration and inflammation. Astrocyte elevated gene-1 (AEG-1) has been suggested as a novel inflammation-related factor in the pathological processes of various inflammatory diseases. To date, little is known about the role of AEG-1 in osteoarthritis. The aim of the present study was to explore the potential role of AEG-1 in the regulation of lipopolysaccharide-induced apoptosis and inflammation of chondrocytes. The results showed that AEG-1 expression was significantly upregulated in chondrocytes following exposure to lipopolysaccharide. Knockdown of AEG-1 increased the survival and decreased the expression of matrix metalloproteinases in chondrocytes treated with lipopolysaccharide. Moreover, silencing of AEG-1 restricted the lipopolysaccharide-induced production of proinflammatory cytokines. In contrast, AEG-1 overexpression caused opposite effects. Notably, we found that AEG-1 inhibition blocked the lipopolysaccharide-induced activation of nuclear factor-κB signaling through impeding the nuclear translocation of nuclear factor-κB p65 subunit. Additionally, inhibition of nuclear factor-κB partially reversed the AEG-1-mediated promotion of lipopolysaccharide-induced inflammatory injury in chondrocytes. In conclusion, our results demonstrate that inhibition of AEG-1 expression attenuates lipopolysaccharide-induced degeneration and inflammation of chondrocytes through suppressing the activation of nuclear factor-κB signaling. This work therefore highlights a potential role of AEG-1 in the pathogenesis of osteoarthritis, and indicates its potential as a therapeutic target.

Lipopolysaccharide Activates Toll-Like Receptor 4 and Prevents Cardiac Fibroblast-to-Myofibroblast Differentiation

Bacterial lipopolysaccharide (LPS) is a known ligand of Toll-like receptor 4 (TLR4) which is expressed in cardiac fibroblasts (CF). Differentiation of CF to cardiac myofibroblasts (CMF) is induced by transforming growth factor-β1 (TGF-β1), increasing alpha-smooth muscle actin (α-SMA) expression. In endothelial cells, an antagonist effect between LPS-induced signaling and canonical TGF-β1 signaling was described; however, it has not been studied whether in CF and CMF the expression of α-SMA induced by TGF-β1 is antagonized by LPS and the mechanism involved. In adult rat CF and CMF, α-SMA, ERK1/2, Akt, NF-κβ, Smad3, and Smad7 protein levels were determined by western blot, TGF-β isoforms by ELISA, and α-SMA stress fibers by immunocytochemistry. CF and CMF secrete the three TGF-β isoforms, and the secretion levels of TGF-β2 was affected by LPS treatment. In CF, LPS treatment decreased the protein levels of α-SMA, and this effect was prevented by TAK-242 (TLR4 inhibitor) and LY294002 (Akt inhibitor), but not by BAY 11-7082 (NF-κβ inhibitor) and PD98059 (ERK1/2 inhibitor). TGF-β1 increased α-SMA protein levels in CF, and LPS prevented partially this effect. In addition, in CMF α-SMA protein levels were decreased by LPS treatment, which was abolished by TAK-242. Finally, in CF LPS decreased the p-Smad3 phosphorylation and increased the Smad7 protein levels. LPS treatment prevents the CF-to-CMF differentiation and reverses the CMF phenotype induced by TGF-β1, through decreasing p-Smad3 and increasing Smad7 protein levels.

The effect of N-acetylcysteine and calcium hydroxide on TNF-α and TGF-β1 in lipopolysaccharide-activated macrophages

OBJECTIVE

The present study was designed to evaluate the pro- and anti-inflammatory effects of NAC and calcium hydroxide (Ca(OH)2) on lipopolysaccharide-stimulated human macrophage cell lines.

DESIGN

THP-1 human monocyte precursor cells were differentiated into macrophage adherent cells. Cell cytotoxicity was measured by flow cytometry analysis. NAC and Ca(OH)2 were applied in the presence or absence of lipopolysaccharides (LPS) for time periods of 4, 8, and 24h. Protein and mRNA levels of tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta1 (TGF-β1) were determined using ELISA and qRT-PCR. The data were statistically analyzed by three-way ANOVA followed by Bonferroni test at α=0.05.

RESULTS

In LPS-stimulated cell lines, while the TNF-α protein and mRNA levels were reduced in the first 4h, only the TGF-β1 mRNA levels increased in the 24th hour following treatment with Ca(OH)2 and NAC when compared with the control group (p<0.001). In LPS-unstimulated cells, the TNF-α protein level was significantly decreased by NAC and Ca(OH)2 at the 4th hour. Additionally, while the TGF-β1 mRNA levels were significantly reduced, the protein level of TGF-β1 was increased at the 24th hour.

CONCLUSIONS

It was concluded that NAC, similar to Ca(OH)2, has anti-inflammatory properties and might be considered an alternate candidate therapeutical agent to Ca(OH)2.

Immunosuppressive and Prometastatic Functions of Myeloid-Derived Suppressive Cells Rely upon Education from Tumor-Associated B Cells

Myeloid-derived suppressive cells (MDSC) have been reported to promote metastasis, but the loss of cancer-induced B cells/B regulatory cells (tBreg) can block metastasis despite MDSC expansion in cancer. Here, using multiple murine tumor models and human MDSC, we show that MDSC populations that expand in cancer have only partially primed regulatory function and limited prometastatic activity unless they are fully educated by tBregs. Cancer-induced tBregs directly activate the regulatory function of both the monocyte and granulocyte subpopulations of MDSC, relying, in part, on TgfβR1/TgfβR2 signaling. MDSC fully educated in this manner exhibit an increased production of reactive oxygen species and NO and more efficiently suppress CD4(+) and CD8(+) T cells, thereby promoting tumor growth and metastasis. Thus, loss of tBregs or TgfβR deficiency in MDSC is sufficient to disable their suppressive function and to block metastasis. Overall, our data indicate that cancer-induced B cells/B regulatory cells are important regulators of the immunosuppressive and prometastatic functions of MDSC.

Exercise modulates the expression of IL-1β and IL-10 in the articular cartilage of normal and osteoarthritis-induced rats

After a joint lesion, high-impact exercise is a risk factor for the development of osteoarthritis (OA). The degradation of articular cartilage in OA has been associated with the activation of inflammatory cytokine signaling pathways. However, differences in cytokine expression in healthy and injured cartilage after exercise have not yet been analyzed. We used immunofluorescence and Western blot to study the expression of IL-1β and IL-10 in the articular cartilage of normal (N), sham-operated (S), and menisectomized (OA) rats subjected or not to high-impact exercise (E) for 3, 6, and 10 days (N, NE, S, SE, and OA groups). Cartilage integrity and proteoglycan content were only affected in the OA groups. Exercise increased the amount of IL-1β and IL-10 positive chondrocytes in NE and SE groups compared with non-exercised groups (N and S). The expression of IL-1β was up-regulated over time in the NE and OA groups, although in the late stages the increase was higher in the OA groups. In contrast, the expression of anti-inflammatory IL-10 was low in the OA group, whereas in the NE groups expression levels were higher at each time point analyzed. These results suggest that anti- and pro-inflammatory molecules in the cartilage might be tightly regulated to maintain the integrity of the tissue and that when this equilibrium is broken (when the meniscus is removed), the pro-inflammatory cytokines take over and OA develops.

The sympathetic nervous system modulates CD4(+)FoxP3(+) regulatory T cells via a TGF-beta-dependent mechanism

CD4(+)FoxP3(+) Tregs are essential mediators of the peripheral immune response to self-antigens. Accordingly, the homeostatic regulation of Treg activity and number would impact on the immune response to both self- and non-self antigens. Because the sympathetic nervous system (SNS) interacts chemically and physically with the central and peripheral immune system and exerts a direct influence on antigen-presenting cells and effector lymphocytes, we have investigated the effect of chemical ablation of the SNS on the number and function of peripheral Treg. Removal of murine peripheral sympathetic innervation by 6-hydroxydopamine induced an increase in splenic and lymph node CD4(+)FoxP3(+) Tregs by a TGF-beta-dependent mechanism. Further, this increase in Tregs coincides with an inhibition of the induction of experimental autoimmune encephalomyelitis. Our results demonstrate that the SNS is an important contributor to the maintenance of peripheral Treg and TGF-beta acts as a bridge between the immune system and the nervous system. Neurological events mediated by the SNS, such as a stress response, may affect the number of T cells that regulate an immune response. Additionally, targeting Tregs via the SNS may be a novel approach to the prevention or treatment of autoimmune diseases.

Lung responses to secondary endotoxin challenge in rats exposed to pig barn air

BACKGROUND

Swine barn air contains endotoxin and many other noxious agents. Single or multiple exposures to pig barn air induces lung inflammation and loss of lung function. However, we do not know the effect of exposure to pig barn air on inflammatory response in the lungs following a secondary infection. Therefore, we tested a hypothesis that single or multiple exposures to barn air will result in exaggerated lung inflammation in response to a secondary insult with Escherichia coli LPS (E. coli LPS).

METHODS

We exposed Sprague-Dawley rats to ambient (N = 12) or swine barn air (N = 24) for one or five days and then half (N = 6/group) of these rats received intravenous E. coli LPS challenge, observed for six hours and then euthanized to collect lung tissues for histology, immunohistochemistry and ELISA to assess lung inflammation.

RESULTS

Compared to controls, histological signs of lung inflammation were evident in barn exposed rat lungs. Rats exposed to barn air for one or five days and challenged with E. coli LPS showed increased recruitment of granulocytes compared to those exposed only to the barn. Control, one and five day barn exposed rats that were challenged with E. coli LPS showed higher levels of IL-1beta in the lungs compared to respective groups not challenged with E. coli LPS. The levels of TNF-alpha in the lungs did not differ among any of the groups. Control rats without E. coli LPS challenge showed higher levels of TGF-beta2 compared to controls challenged with E. coli LPS.

CONCLUSION

These results show that lungs of rats exposed to pig barn air retain the ability to respond to E. coli LPS challenge.

Role of TGF-beta1 and nitric oxide in the bystander response of irradiated glioma cells

The radiation-induced bystander effect (RIBE) increases the probability of cellular response and therefore has important implications for cancer risk assessment following low-dose irradiation and for the likelihood of secondary cancers after radiotherapy. However, our knowledge of bystander signaling factors, especially those having long half-lives, is still limited. The present study found that, when a fraction of cells within a glioblastoma population were individually irradiated with helium ions from a particle microbeam, the yield of micronuclei (MN) in the nontargeted cells was increased, but these bystander MN were eliminated by treating the cells with either aminoguanidine (an inhibitor of inducible nitric oxide (NO) synthase) or anti-transforming growth factor beta1 (anti-TGF-beta1), indicating that NO and TGF-beta1 are involved in the RIBE. Intracellular NO was detected in the bystander cells, and additional TGF-beta1 was detected in the medium from irradiated T98G cells, but it was diminished by aminoguanidine. Consistent with this, an NO donor, diethylamine nitric oxide (DEANO), induced TGF-beta1 generation in T98G cells. Conversely, treatment of cells with recombinant TGF-beta1 could also induce NO and MN in T98G cells. Treatment of T98G cells with anti-TGF-beta1 inhibited the NO production when only 1% of cells were targeted, but not when 100% of cells were targeted. Our results indicate that, downstream of radiation-induced NO, TGF-beta1 can be released from targeted T98G cells and plays a key role as a signaling factor in the RIBE by further inducing free radicals and DNA damage in the nontargeted bystander cells.

Reactive oxygen species induce expression of vascular endothelial growth factor in chondrocytes and human articular cartilage explants

Vascular endothelial growth factor (VEGF) promotes cartilage-degrading pathways, and there is evidence for the involvement of reactive oxygen species (ROS) in cartilage degeneration. However, a relationship between ROS and VEGF has not been reported. Here, we investigate whether the expression of VEGF is modulated by ROS. Aspirates of synovial fluid from patients with osteoarthritis (OA) were examined for intra-articular VEGF using ELISA. Immortalized C28/I2 chondrocytes and human knee cartilage explants were exposed to phorbol myristate acetate (PMA; 0-20 microg/ml), which is a ROS inducer, or 3-morpholino-sydnonimine hydrochloride (SIN-1; 0-20 microM), which is a ROS donor. The levels of VEGF protein and nitric oxide (NO) production were determined in the medium supernatant, using ELISA and Griess reagent, respectively. Gene expression of VEGF-121 and VEGF-165 was determined by splice variant RT-PCR. Expression of VEGF and VEGF receptors (VEGFR-1 and VEGFR-2) was quantified by real-time RT-PCR. Synovial fluid from OA patients revealed markedly elevated levels of VEGF. Common RT-PCR revealed that the splice variants were present in both immortalized chondrocytes and cartilage discs. In immortalized chondrocytes, stimulation with PMA or SIN-1 caused increases in the levels of VEGF, VEGFR-1 and VEGFR-2 mRNA expression. Cartilage explants produced similar results, but VEGFR-1 was only detectable after stimulation with SIN-1. Stimulation with PMA or SIN-1 resulted in a dose-dependent upregulation of the VEGF protein (as determined using ELISA) and an increase in the level of NO in the medium. Our findings indicate ROS-mediated induction of VEGF and VEGF receptors in chondrocytes and cartilage explants. These results demonstrate a relationship between ROS and VEGF as multiplex mediators in articular cartilage degeneration.

Modulation of intracellular reactive oxygen species level in chondrocytes by IGF-1, FGF, and TGF-beta1

Growth factors are important in the development, maintenance and repair of cartilage. The principal aim of this study was to test the capacity of three growth factors with established roles in cartilage, namely insulin-like growth factor (IGF)-1, fibroblast growth factor (FGF) and transforming growth factor (TGF)-beta 1, to alter intracellular reactive oxygen species (ROS) levels. Explants of articular cartilage from young, mature, and aged rats were pretreated with IGF-1, FGF, or TGF-beta 1 and intracellular ROS levels were quantified using the free radical sensing probe dihydrorhodamine 123 (DHR 123), confocal microscopy, and densitometric image analysis. Viability of chondrocytes following ROS stress and growth factor treatment was assessed using the live/dead cytotoxicity assay, and the activities of the antioxidant enzymes--catalase (CAT), total superoxide dismutase (SOD), and glutathione peroxidase (GPX)--were measured spectrophotometrically by decay of the substrate from the reaction mixture. The effect of IGF-1 on ROS levels in cultured human chondrocytes also was examined. In rat cartilage, FGF did not significantly affect ROS levels or antioxidant enzyme activity in any age group. TGF-beta1 significantly increased cellular ROS levels in mature and old cartilage whereas in marked contrast, IGF-1 significantly and age-dependently reduced ROS levels. IGF-1 also had a potent antioxidant effect on cultured human chondrocytes. Pretreatment of rat cartilage with IGF-1 significantly enhanced the activity of GPX, without altering the activity of SOD or CAT, and protected chondrocytes against ROS-induced cell death. TGF-beta 1 had no significant effect on the activity of the antioxidant enzymes. Despite promoting ROS production, TGF-beta 1 was not cytotoxic. We concluded that TGF-beta 1 exhibits an acute pro-oxidant effect in cartilage that is not cytotoxic, suggesting a role in physiological cell signalling. In marked contrast, IGF-1 is a potent antioxidant in mature and aged rat and human chondrocytes, protecting cells against ROS-induced cell death probably through the enhancement of the activity of the antioxidant enzyme GPX.

Effects of TGF-beta1 and triiodothyronine on cartilage maturation: in vitro analysis using long-term high-density micromass cultures of chick embryonic limb mesenchymal cells

Endochondral ossification is initiated by differentiation of mesenchymal cells into chondrocytes, which produce a cartilaginous matrix, proliferate, mature, and undergo hypertrophy, followed by matrix calcification, and substitution of cartilage by bone. A number of hormones and growth factors have been implicated in this process. Using in vitro, long-term, high-density, micromass cultures of chick embryonic mesenchyme, that recapitulate the process of chondrogenesis, chondrocyte maturation, and hypertrophy, we have investigated the importance of a balance between proliferation and apoptosis in cartilage maturation, focusing specifically on the effects of transforming growth factor-beta1 (TGF-beta1) and the thyroid hormone, triiodothyronine (T3). Our results showed that TGF-beta1 stimulates proliferation, by week 2 of culture, and T3 inhibits proliferation by week 3. Cell size increases in cultures treated with T3. Collagen type X is expressed in all culture, and delay in matrix deposition is seen only in the cultures treated with TGF-beta1. T3 stimulates alkaline phosphatase activity, but not calcification. T3 enhances apoptosis, as seen by TUNEL staining, and internucleosomal DNA fragmentation. The results support the roles of T3 and TGF-beta in cartilage maturation, i.e., TGF-beta stimulates proliferation and suppresses hypertrophy, while T3 stimulates hypertrophy and apoptosis.

Calcium Fluxes Modulate the Radiation-Induced Bystander Responses in Targeted Glioma and Fibroblast Cells

Bystander responses have been reported to be a major determinant of the response of cells to radiation exposure at low doses, including those of relevance to therapy. This study investigated the role of changes in calcium levels in bystander responses leading to chromosomal damage in nonirradiated T98G glioma cells and AG01522 fibroblasts that had been either exposed to conditioned medium from irradiated cells or co-cultured with a population where a fraction of cells were individually targeted through the nucleus or cytoplasm with a precise number of microbeam helium-3 particles. After the recipient cells were treated with conditioned medium from T98G or AG01522 cells that had been irradiated through either nucleus or cytoplasm, rapid calcium fluxes were monitored in the nonirradiated recipient cells. Their characteristics were dependent on the source of the conditioned medium but had no dependence on radiation dose. When recipient cells were co-cultured with an irradiated population of either T98G or AG01522 cells, micronuclei were induced in the nonirradiated cells, but this response was eliminated by treating the cells with calcicludine (CaC), a potent blocker of Ca(2+) channels. Moreover, both the calcium fluxes and the bystander effect were inhibited when the irradiated T98G cells were treated with aminoguanidine, an inhibitor of nitric oxide synthase (NOS), and when the irradiated AG01522 cells were treated with DMSO, a scavenger of reactive oxygen species (ROS), which indicates that NO and ROS were involved in the bystander responses generated from irradiated T98G and AG01522 cells, respectively. Our findings indicate that calcium signaling may be an early response in radiation-induced bystander effects leading to chromosome damage.

ATR-dependent radiation-induced γH2AX foci in bystander primary human astrocytes and glioma cells

Radiotherapy is an important treatment for patients suffering from high-grade malignant gliomas. Non-targeted (bystander) effects may influence these cells' response to radiation and the investigation of these effects may therefore provide new insights into mechanisms of radiosensitivity and responses to radiotherapy as well as define new targets for therapeutic approaches. Normal primary human astrocytes (NHA) and T98G glioma cells were irradiated with helium ions using the Gray Cancer Institute microbeam facility targeting individual cells. Irradiated NHA and T98G glioma cells generated signals that induced gammaH2AX foci in neighbouring non-targeted bystander cells up to 48 h after irradiation. gammaH2AX bystander foci were also observed in co-cultures targeting either NHA or T98G cells and in medium transfer experiments. Dimethyl sulphoxide, Filipin and anti-transforming growth factor (TGF)-beta 1 could suppress gammaH2AX foci in bystander cells, confirming that reactive oxygen species (ROS) and membrane-mediated signals are involved in the bystander signalling pathways. Also, TGF-beta 1 induced gammaH2AX in an ROS-dependent manner similar to bystander foci. ROS and membrane signalling-dependent differences in bystander foci induction between T98G glioma cells and normal human astrocytes have been observed. Inhibition of ataxia telangiectasia mutated (ATM) protein and DNA-PK could not suppress the induction of bystander gammaH2AX foci whereas the mutation of ATM- and rad3-related (ATR) abrogated bystander foci induction. Furthermore, ATR-dependent bystander foci induction was restricted to S-phase cells. These observations may provide additional therapeutic targets for the exploitation of the bystander effect.

Bystander signaling between glioma cells and fibroblasts targeted with counted particles

Radiation-induced bystander effects may play an important role in cancer risks associated with environmental, occupational and medical exposures and they may also present a therapeutic opportunity to modulate the efficacy of radiotherapy. However, the mechanisms underpinning these responses between tumor and normal cells are poorly understood. Using a microbeam, we investigated interactions between T98G malignant glioma cells and AG01522 normal fibroblasts by targeting cells through their nuclei in one population, then detecting cellular responses in the other co-cultured non-irradiated population. It was found that when a fraction of cells was individually irradiated with exactly 1 or 5 helium particles ((3)He(2+)), the yield of micronuclei (MN) in the non-irradiated population was significantly increased. This increase was not related to the fraction of cells targeted or the number of particles delivered to those cells. Even when one cell was targeted with a single (3)He(2+), the induction of MN in the bystander non-irradiated population could be increased by 79% for AG01522 and 28% for T98G. Furthermore, studies showed that nitric oxide (NO) and reactive oxygen species (ROS) were involved in these bystander responses. Following nuclear irradiation in only 1% of cells, the NO level in the T98G population was increased by 31% and the ROS level in the AG0 population was increased by 18%. Treatment of cultures with 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (c-PTIO), an NO scavenger, abolished the bystander MN induction in non-irradiated AG01522 cells but only partially in non-irradiated T98G cells, and this could be eliminated by treatment with either DMSO or antioxidants. Our findings indicate that differential mechanisms involving NO and ROS signaling factors play a role in bystander responses generated from targeted T98G glioma and AG0 fibroblasts, respectively. These bystander interactions suggest that a mechanistic control of the bystander effect could be of benefit to radiotherapy.

Targeted cytoplasmic irradiation induces bystander responses

The observation of radiation-induced bystander responses, in which cells respond to their neighbors being irradiated, has important implications for understanding mechanisms of radiation action particularly after low-dose exposure. Much of this questions the current dogma of direct DNA damage driving response in irradiated systems. In this study, we have used a charged-particle microbeam to target individual helium ions ((3)He(2+)) to individual cells within a population of radioresistant glioma cells cultured alone or in coculture with primary human fibroblasts. We found that even when a single cell within the glioma population was precisely traversed through its cytoplasm with one (3)He(2+) ion, bystander responses were induced in the neighboring nonirradiated glioma or fibroblasts so that the yield of micronuclei was increased by 36% for the glioma population and 78% for the bystander fibroblast population. Importantly, the yield of bystander-induced micronuclei was independent of whether the cytoplasm or nucleus of a cell was targeted. The bystander responses were fully eliminated when the populations were treated with 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide or filipin, which scavenge nitric oxide (NO) and disrupt membrane rafts, respectively. By using the probe 4-amino-5-methylamino-2',7'-difluorofluorescein, it was found that the NO level in the glioma population was increased by 15% after 1 or 10 cytoplasmic traversals, and this NO production was inhibited by filipin. This finding shows that direct DNA damage is not required for switching on of important cell-signaling mechanisms after low-dose irradiation and that, under these conditions, the whole cell should be considered a sensor of radiation exposure.

Early gene expression analyzed by cDNA microarray and RT-PCR in osteoblasts cultured with water-soluble and low molecular chitooligosaccharide

Chitosan has a variety of biological activities. However, little is known about how chitosan modulates the hard tissue forming cells. When we cultured an osteoblastic cell line in alpha-MEM supplemented with 10% FBS and 0.005% chitooligosaccharide for 3 days, alkaline phosphatase (ALP) activity was significantly high compared with the control culture group (p<0.05). This study was focused on gene expression in osteoblasts cultured with water-soluble chitooligosaccharide. cDNA probes were synthesized from isolated RNA and labeled with fluorescent dye. They were hybridized with Human 1.0((R)) cDNA microarray, and fluorescent signal was analyzed. cDNA microarray analysis revealed that 16 genes were expressed at >/=1.5-fold higher signal ratio levels in the experimental group compared with the control group after 3 days. RT-PCR analysis showed that chitosan oligomer induced an increase in the expression of two genes, CD56 antigen and tissue-type plasminogen activator. Furthermore, the expression of mRNAs for BMP-2 was almost identical in the experimental and control groups after 3 days of culture, but slightly increased after 7 days of culture with chitosan oligomer. These results suggest that a super-low concentration of chitooligosaccharide could modulate the activity of osteoblastic cells through mRNA levels and that the genes concerning cell proliferation and differentiation can be controlled by water-soluble chitosan.