Reduction in lipopolysaccharide-induced apoptosis of fibroblasts obtained from a patient with gingival overgrowth during nifedipine-treatment

Cyclosporine A causes gingival overgrowth via reduced G1 cell cycle arrest in gingival fibroblasts

Gingival overgrowth caused by cyclosporine A is due to increased fibroblast proliferation in gingival tissues. Cell cycle system balances proliferation and anti-proliferation of gingival fibroblasts and plays a role in the maintenance of its population in gingival tissues. When cells detect and respond to abnormalities (e.g. DNA damage), cell cycle progression is arrested in the G1 phase until the completion of damage restoration. In this study, we investigated the effects of cyclosporine A on G1 cell cycle arrest and on its regulators in gingival fibroblasts to clarify the mechanism of cyclosporine A-induced gingival overgrowth. Human gingival fibroblasts from healthy donors were cultured to semi-confluence and were then treated with or without 200 ng/mL (166 nM) cyclosporine A in D-MEM with 2% fetal bovine serum. Cell proliferation was assessed by counting total cell numbers. The distribution of cell cycle phases was assessed using flow cytometric analysis. The levels of mRNA and protein expression for cell cycle regulators were quantified using reverse transcription-quantitative PCR and western blot analysis, respectively. Treatment with cyclosporine A markedly increased cell proliferation, inhibited G1 cell cycle arrest, significantly increased CDC25A and CYCLIN E1 mRNA expression levels, significantly decreased P21, SMAD3 and SMAD4 mRNA expression levels, significantly upregulated the protein expression levels of CDC25A, CYCLIN E1, pCDK2 and pRB1 and significantly downregulated the protein expression levels of P21, SMAD3 and SMAD4. Treatment with cyclosporine A also increased MYC and ATM mRNA expression levels and decreased CDK2, ATR, P27, P53 and RB1 mRNA expression levels but not significantly. These results demonstrate that cyclosporine A causes gingival overgrowth due to the following mechanism in gingival fibroblasts: cyclosporine A increases levels of phospho-CDK2 and CYCLIN E1 by upregulating CDC25A and downregulating P21 with the downregulation of SMAD3 and SMAD4, which results in the inhibition of G1 cell cycle arrest.

Cyclosporine A Causes Gingival Overgrowth by Promoting Entry into the S Phase at the G1/S Cell Cycle Checkpoint in Gingival Fibroblasts Exposed to Lipopolysaccharide

OBJECTIVES

Cyclosporine A promotes gingival fibrosis by enhancing the proliferation of gingival fibroblasts, leading to gingival overgrowth. The population of gingival fibroblasts is regulated by cell cycle machinery, which balances cell growth and inhibition. Cells that detect DNA damage pause at the G1/S checkpoint to repair the damage instead of progressing to the S phase. Previous studies have linked drug-induced gingival overgrowth to the response of fibroblasts to lipopolysaccharide (LPS) and cyclosporine A. This research investigates the effects of cyclosporine A on the G1/S checkpoint and its mediators in LPS-treated gingival fibroblasts to clarify the mechanisms behind cyclosporine-A-induced gingival overgrowth.

METHODS

Semi-confluent human gingival fibroblasts were treated with LPS or cyclosporine A in DMEM. Cell proliferation was evaluated by counting the total number of cells. The distribution of the cell cycle phases was analyzed using flow cytometry. Additionally, the expression levels of mRNAs and proteins related to cell cycle regulators were quantified by reverse-transcription quantitative PCR and Western blotting, respectively.

RESULTS

Cyclosporine A treatment significantly enhanced cell proliferation and the G1-S cell cycle transition. It increased the mRNA levels of CDC25A and CYCLIN D while decreasing those of RB1, SMAD3, and SMAD4. Additionally, it upregulated the protein levels of CDC25A, CYCLIN D, CDK4, CDK6, and pRB and downregulated the protein levels of SMAD3 and SMAD4.

CONCLUSIONS

Gingival overgrowth induced by cyclosporine A could be attributed to these alterations.

18‑α‑glycyrrhetinic acid induces apoptosis in gingival fibroblasts exposed to phenytoin

Phenytoin (PHT)-induced gingival overgrowth is caused by the increased proliferation and reduced apoptosis of gingival fibroblasts in inflammatory gingiva. Licorice has long been used as a component of therapeutic preparations. It inhibits cell proliferation, induces cell apoptosis and has anti-inflammatory effects. 18-α-glycyrrhetinic acid (18α-GA), the active compound in licorice, promotes apoptosis in various types of cells. The present study determined whether 18α-GA affects apoptosis in gingival fibroblasts exposed to PHT. The present study aimed to establish a basis for the therapeutic application of 18α-GA to treat the gingival overgrowth induced by PHT. Human gingival fibroblasts from healthy donors were cultured to semi-confluence and then stimulated in serum-free DMEM containing PHT with or without 18α-GA for subsequent experiments. Apoptotic cells were detected by ELISA. Analysis of the distribution of cell cycle phases and the apoptotic cell population was performed by flow cytometry. The expression levels of mRNAs and proteins of apoptotic regulators were measured using reverse transcription-quantitative PCR and western blotting, respectively. Caspase (CASP) activities were assessed by an ELISA. Treatment with 18α-GA markedly increased the number of apoptotic cells, reduced BCL2 mRNA expression, increased CASP2 and receptor (TNFRSF)-interacting serine-threonine kinase 1 (RIPK1) domain containing adaptor with death domain, Fas (TNFRSF6)-associated via death domain, RIPK1, tumor necrosis factor receptor superfamily; member 1A, TNF receptor-associated factor 2, CASP2, CASP3 and CASP9 mRNA expression, and also upregulated the protein expression levels and activities of caspase-2, caspase-3 and caspase-9. These results demonstrated that 18α-GA induced apoptosis through the activation of the Fas and TNF pathways in the death receptor signaling pathway in gingival fibroblasts treated with PHT. 18α-GA exhibited therapeutic potential for the treatment of PHT-induced gingival overgrowth.

Phenytoin-induced gingival overgrowth caused by death receptor pathway malfunction

OBJECTIVE

In this study, we investigated the role of phenytoin (PHT) in death receptor-induced apoptosis of gingival fibroblasts to clarify the mechanism of PHT-induced gingival overgrowth.

METHODS

Human gingival fibroblasts were cultured to semiconfluence and treated with PHT (0.025, 0.1, 0.25, and 1.0 μM) for 48 h, and then, the apoptotic cell numbers were relatively determined by absorptiometry. After 24 h of 0.25 μM PHT treatment, caspase activity was measured by absorptiometry, apoptotic and cell cycle phase distribution was analyzed by flow cytometry, expression levels of apoptotic genes were quantified by real-time qPCR, and expression of apoptotic proteins was detected by Western blot analysis. After 48 h of 0.25 μM PHT treatment, appearance of apoptotic cells was detected by TUNEL assay.

RESULTS

PHT treatment decreased the proportion of apoptotic cells in gingival fibroblasts compared to a serum-free control culture in response to the protein changes as follows: PHT upregulated c-FLIP and, in turn, downregulated FADD, caspase-8, and caspase-3; PHT upregulated c-IAP2 and downregulated TRAF2; PHT downregulated caspase-9 and caspase-3 via decreased RIPK1 activity and increased Bcl-2 activity.

CONCLUSION

PHT-induced gingival overgrowth may result from the above-mentioned mechanisms involving apoptosis inhibition in gingival fibroblasts.

Possible pharmacotherapy for nifedipine-induced gingival overgrowth: 18α-glycyrrhetinic acid inhibits human gingival fibroblast growth

BACKGROUND AND PURPOSE

This investigation aimed to establish the basis of a pharmacotherapy for nifedipine-induced gingival overgrowth. Gingival overgrowth has been attributed to the enhanced growth of gingival fibroblasts. In this study, we investigated the effects of 18-α-glycyrrhetinic acid (18α-GA) on growth, the cell cycle, and apoptosis and on the regulators of these processes in gingival fibroblasts isolated from patients who presented with nifedipine-induced gingival overgrowth.

EXPERIMENTAL APPROACH

Gingival fibroblasts were cultured in medium containing 1% FBS with/without 10 μM 18α-GA for 24 or 48 h, and the cell number, cell cycle phase distribution, relative DNA content, apoptotic cell number and morphological characteristics of the cells undergoing apoptosis were measured together with the levels of proteins that regulate these processes and the level of caspase activity.

KEY RESULTS

18α-GA significantly decreased cell numbers and significantly increased the percentage of cells in the sub-G1 and G0 /G1 phases of the cell cycle and the number of apoptotic cells. Nuclear condensation and fragmentation of cells into small apoptotic bodies appeared in the fibroblasts treated with 18α-GA. In addition, 18α-GA significantly decreased the protein levels of cyclins A and D1, CDKs 2 and 6, phosphorylated Rb (ser(780) and ser(807/811)), Bcl-xL and Bcl-2 and increased the protein levels of p27, cytosolic cytochrome c, pro-caspase-3, and cleaved caspase-3 and the activities of caspases 3 and 9.

CONCLUSIONS AND IMPLICATIONS

18α-GA inhibited gingival fibroblast growth by suppressing the G1 /S phase transition and inducing apoptosis. In conclusion, 18α-GA may be used as a pharmacotherapy for nifedipine-induced gingival overgrowth.

Modulation of inflammatory response of wounds by antimicrobial photodynamic therapy

BACKGROUND AND AIMS

Management of infections caused by Pseudomonas aeruginosa is becoming difficult due to the rapid emergence of multi-antibiotic resistant strains. Antimicrobial photodynamic therapy (APDT) has a lot of potential as an alternative approach for inactivation of antibiotic resistant bacteria. In this study we report results of our investigations on the effect of poly-L-lysine conjugate of chlorine p6 (pl-cp6) mediated APDT on the healing of P.aeruginosa infected wounds and the role of Nuclear Factor kappa B (NF-kB) induced inflammatory response in this process.

MATERIALS AND METHOD

Excisional wounds created in Swiss albino mice were infected with ∼10(7) colony forming units of P.aeruginosa. Mice with wounds were divided into three groups: 1) Uninfected, 2) Infected, untreated control (no light, no pl-cp6), 3) Infected, APDT. After 24 h of infection (day 1 post wounding), the wounds were subjected to APDT [pl-cp6 applied topically and exposed to red light (660 ± 25 nm) fluence of ∼ 60 J/cm(2)]. Subsequent to APDT, on day 2 and 5 post wounding (p.w), measurements were made on biochemical parameters of inflammation [toll like receptor-4 (TLR-4), NF-kB, Inteleukin (IL)-[1α, IL-β, and IL-2)] and cell proliferation [(fibroblast growth factor-2 (FGF-2), alkaline phosphatase (ALP)].

RESULTS

In comparison with untreated control, while expression of TLR-4, NF-kB (p105 and p50), and proinflammatory interleukins (IL-1α, IL-1β,IL-2) were reduced in the infected wounds subjected to APDT, the levels of FGF-2 and ALP increased, on day 5 p.w.

CONCLUSION

The measurements made on the inflammatory markers and cell proliferation markers suggest that APDT reduces inflammation caused by P.aeruginosa and promotes cell proliferation in wounds.

Epigenetic regulation of Thy-1 gene expression by histone modification is involved in lipopolysaccharide-induced lung fibroblast proliferation

Lipopolysaccharide (LPS)-induced pulmonary fibrosis is characterized by aberrant proliferation and activation of lung fibroblasts. Epigenetic regulation of thymocyte differentiation antigen 1 (Thy-1) is associated with lung fibroblast phenotype transformation that results in aberrant cell proliferation. However, it is not clear whether the epigenetic regulation of Thy-1 expression is required for LPS-induced lung fibroblast proliferation. To address this issue and better understand the relative underlying mechanisms, we used mouse lung fibroblasts as model to observe the changes of Thy-1 expression and histone deacetylation after LPS challenge. The results showed that cellular DNA synthesis, measured by BrdU incorporation, was impacted less in the early stage (24 hrs) after the challenge of LPS, but significantly increased at 48 or 72 hrs after the challenge of LPS. Meanwhile, Thy-1 expression, which was detected by real-time PCR and Western blot, in lung fibroblasts decreased with increased time after LPS challenge and diminished at 72 hrs. We also found that the acetylation of either histone H3 or H4 decreased in the LPS-challenged lung fibroblasts. ChIP assay revealed that the acetylation of histone H4 (Ace-H4) decreased in the Thy-1 promoter region in response to LPS. In addition, all the above changes could be attenuated by depletion of TLR4 gene. Our studies indicate that epigenetic regulation of Thy-1 gene expression by histone modification is involved in LPS-induced lung fibroblast proliferation.

Inhibition of G₁ cell cycle arrest in human gingival fibroblasts exposed to phenytoin

Gingival overgrowth is caused in response to the antiepileptic drug phenytoin (PHT). PHT-induced gingival overgrowth is characterized by the proliferation of fibroblasts and increased collagen formation in gingiva. Fibroblast proliferation is regulated through the cell cycle. Thus, in the present study, we examined the effects of PHT on the cell cycle, the expression of cell cycle control proteins and the proliferation in human gingival fibroblasts (hGFs). Cells were stimulated in serum-free DMEM with or without 0.25 μm PHT. Subsequently, the cell cycle phase distribution and the protein expression after 24 h and the cell proliferation after 24, 48 and 72 h were evaluated. PHT significantly inhibited synchronization at the G₀/G₁ phase of the cell cycle in hGFs through serum starvation. Stimulation with PHT for 48 and 72 h significantly induced a proliferative response in hGFs. PHT decreased the expression of the Cdk-inhibitory proteins p21 and p27 and increased the levels of the S phase-promoting proteins phospho-Thr160-Cdk2 and phospho-Ser807/811-Rb in serum-free DMEM. The inhibition of G₁ cell cycle arrest in hGFs may result from an increase in phosphorylated Cdk2 and Rb proteins and decreased levels of p21 and p27 proteins by PHT. The gingival overgrowth may be caused by the failure of the G1 cell cycle arrest in GFs exposed to PHT.

Lipopolysaccharide induces lung fibroblast proliferation through Toll-like receptor 4 signaling and the phosphoinositide3-kinase-Akt pathway

Pulmonary fibrosis is characterized by lung fibroblast proliferation and collagen secretion. In lipopolysaccharide (LPS)-induced acute lung injury (ALI), aberrant proliferation of lung fibroblasts is initiated in early disease stages, but the underlying mechanism remains unknown. In this study, we knocked down Toll-like receptor 4 (TLR4) expression in cultured mouse lung fibroblasts using TLR4-siRNA-lentivirus in order to investigate the effects of LPS challenge on lung fibroblast proliferation, phosphoinositide3-kinase (PI3K)-Akt pathway activation, and phosphatase and tensin homolog (PTEN) expression. Lung fibroblast proliferation, detected by BrdU assay, was unaffected by 1 mug/mL LPS challenge up to 24 hours, but at 72 hours, cell proliferation increased significantly. This proliferation was inhibited by siRNA-mediated TLR4 knockdown or treatment with the PI3K inhibitor, Ly294002. In addition, siRNA-mediated knockdown of TLR4 inhibited the LPS-induced up-regulation of TLR4, down-regulation of PTEN, and activation of the PI3K-Akt pathway (overexpression of phospho-Akt) at 72 hours, as detected by real-time PCR and Western blot analysis. Treatment with the PTEN inhibitor, bpV(phen), led to activation of the PI3K-Akt pathway. Neither the baseline expression nor LPS-induced down-regulation of PTEN in lung fibroblasts was influenced by PI3K activation state. PTEN inhibition was sufficient to exert the LPS effect on lung fibroblast proliferation, and PI3K-Akt pathway inhibition could reverse this process. Collectively, these results indicate that LPS can promote lung fibroblast proliferation via a TLR4 signaling mechanism that involves PTEN expression down-regulation and PI3K-Akt pathway activation. Moreover, PI3K-Akt pathway activation is a downstream effect of PTEN inhibition and plays a critical role in lung fibroblast proliferation. This mechanism could contribute to, and possibly accelerate, pulmonary fibrosis in the early stages of ALI/ARDS.