Interleukin-4 and interferon-gamma inhibit prostaglandin production by interleukin-1beta-stimulated human periodontal ligament fibroblasts

Clustering human dental pulp fibroblasts spontaneously activate NLRP3 and AIM2 inflammasomes and induce IL-1β secretion

Objectives

The objective of the present study was to investigate whether NOD-like receptor family pyrin domain-containing 3 (NLRP3) and absent in melanoma 2 (AIM2) inflammasomes pathways were involved in an experimental model of fibroblast activation named nemosis, which was used to mimic circumstances without bacteria stimulation.

Methods

Nemosis of human dental pulp fibroblast (DPFs) was induced by three-dimensional culture in U-shaped 96-well plates and investigated by scanning electron microscopy (SEM). DPFs monolayers were used as control. Annexin V-FITC/7-AAD apoptosis assay was performed on the DPFs spheroids by flowcytometry. Caspase-1 activity detection assay was conducted on the DPFs spheroids. Quantitative real-time polymerase chain reaction (qRT-PCR), cytokine measurements, Western blot and the effect of COX-2 inhibitor on spheroids was studied.

Results

SEM study observed human dental pulp fibroblast clusters and cell membranes damage on the surface of DPFs spheroids. The percentages of necrotic cells from DPFs spheroids gradually increased as the incubation time increased. A statistically significant increase in caspase-1 activity was observed after DPFs spheroids formation. DPFs spheroids displayed significant amounts of NLRP3, AIM2 mRNA and protein expression, caspase-1 mRNA expression and cleaved Caspase-1 protein expression and high IL-1β concentrations (P < 0.05) than DPFs monolayers. Specific COX-2 inhibitor (NS-398) decreased NLRP3 mRNA and protein expression, cleaved Caspase-1 protein expression, Caspase-1 activity and IL-1β mRNA expression and IL-1β concentrations (P < 0.05). However, Specific COX-2 inhibitor had no impact on AIM2 mRNA and protein expression, caspase-1 mRNA expression and pro-Caspase-1 protein expression.

Conclusions

In conclusion, clustering human DPFs spontaneously activated NLRP3 and AIM2 inflammasomes and induced IL-1β secretion which could be partially attenuated by COX-2 inhibitor. Thus, nemosis could become a powerful model for studying mechanisms underlying aseptic pulpitis.

Regulation of inflammation by lipid mediators in oral diseases

Lipid mediators (LM) of inflammation are a class of compounds derived from ω-3 and ω-6 fatty acids that play a wide role in modulating inflammatory responses. Some LM possess pro-inflammatory properties, while others possess proresolving characteristics, and the class switch from pro-inflammatory to proresolving is crucial for tissue homeostasis. In this article, we review the major classes of LM, focusing on their biosynthesis and signaling pathways, and their role in systemic and, especially, oral health and disease. We discuss the detection of these LM in various body fluids, focusing on diagnostic and therapeutic applications. We also present data showing gender-related differences in salivary LM levels in healthy controls, leading to a hypothesis on the etiology of inflammatory diseases, particularly Sjögren's syndrome. We conclude by enumerating open areas of research where further investigation of LM is likely to result in therapeutic and diagnostic advances.

Resolvin D1 protects periodontal ligament

Resolution agonists are endogenous mediators that drive inflammation to homeostasis. We earlier demonstrated in vivo activity of resolvins and lipoxins on regenerative periodontal wound healing. The goal of this study was to determine the impact of resolvin D1 (RvD1) on the function of human periodontal ligament (PDL) fibroblasts, which are critical for wound healing during regeneration of the soft and hard tissues around teeth. Primary cells were cultured from biopsies obtained from three individuals free of periodontal diseases. Peripheral blood mononuclear cells were isolated by density gradient centrifugation from whole blood of healthy volunteers. PGE2, leukotriene B4 (LTB4), and lipoxin A4 (LXA4) in culture supernatants were measured by ELISA. The direct impact of RvD1 on PDL fibroblast proliferation was measured and wound closure was analyzed in vitro using a fibroblast culture "scratch assay." PDL fibroblast function in response to RvD1 was further characterized by basic FGF production by ELISA. IL-1β and TNF-α enhanced the production of PGE2. Treatment of PDL cells and monocytes with 0.1-10 ng/ml RvD1 (0.27-27 M) reduced cytokine induced production of PGE2 and upregulated LXA4 production by both PDL cells and monocytes. RvD1 significantly enhanced PDL fibroblast proliferation and wound closure as well as basic FGF release. The results demonstrate that anti-inflammatory and proresolution actions of RvD1 with upregulation of arachidonic acid-derived endogenous resolution pathways (LXA4) and suggest resolution pathway synergy establishing a novel mechanism for the proresolution activity of the ω-3 docosahexaenoic acid-derived resolution agonist RvD1.

Regulation of T helper cell subsets by cyclooxygenases and their metabolites

Cyclooxygenases and their metabolites are important regulators of inflammatory responses and play critical roles in regulating the differentiation of T helper cell subsets in inflammatory diseases. In this review, we highlight new information on regulation of T helper cell subsets by cyclooxygenases and their metabolites. Prostanoids influence cytokine production by both antigen presenting cells and T cells to regulate the differentiation of naïve CD4(+) T cells to Th1, Th2 and Th17 cell phenotypes. Cyclooxygenases and PGE2 generally exacerbate Th2 and Th17 phenotypes, while suppressing Th1 differentiation. Thus, cycloxygenases may play a critical role in diseases that involve immune cell dysfunction. Targeting of cyclooxygenases and their eicosanoid products may represent a new approach for treatment of inflammatory diseases, tumors and autoimmune disorders.

Effect of interleukin-4 on vascular endothelial growth factor production in rheumatoid synovial fibroblasts

Interleukin (IL)-4 has been demonstrated to have anti-inflammatory and anti-tumour activity. Because aberrant angiogenesis is a significant pathogenic component of tumour growth and chronic inflammation, we investigated the effect of IL-4 on the production of vascular endothelial growth factor (VEGF) by synovial fibroblasts derived from patients with rheumatoid arthritis (RA). Fibroblast-like synoviocytes (FLS) were prepared from synovial tissues of RA and incubated with different concentrations of IL-4 in the presence or absence of transforming growth factor (TGF)-beta. VEGF level was measured by enzyme-linked immunosorbent assay and semiquantitative reverse transcription--polymerase chain reaction. Treatment of FLS with IL-4 alone caused a dose-dependent increase in VEGF levels. In contrast, IL-4 exhibited the inhibitory effect on VEGF production when FLS were stimulated with TGF-beta. Combined treatment of IL-4 and IL-10 inhibited TGF-beta-induced VEGF production in an additive fashion. TGF-beta increased the induction of cyclooxygenase-2 mRNA, which was inhibited significantly by the treatment of IL-4. NS-398, a COX-2 inhibitor, inhibited TGF-beta-induced VEGF production in a dose-dependent manner. Furthermore, exogenous addition of prostaglandin E2 (PGE2) restored IL-4 inhibition on TGF-beta induced VEGF production. Collectively, our results suggest that IL-4 have an anti-angiogenic effect, especially in the inflammatory milieu of RA by inhibiting the VEGF production in synovial fibroblasts.

Interleukin-1β–Induced Prostaglandin E2Production by Human Gingival Fibroblasts Is Upregulated by Glycine

BACKGROUND

Human gingival fibroblasts (GFB) may produce prostaglandin E(2) (PGE(2)) in response to proinflammatory cytokines. Elevated concentrations of glycine were previously found in periodontal pockets and saliva of periodontitis patients and, therefore, we aimed to study the influence of glycine on PGE(2) production.

METHODS

Human GFB were cultured in the presence of various concentrations of glycine and/or interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and IL-10 and their influence on PGE(2) production was measured. The expression of cyclooxygenases (COX) was analyzed by Western blot and immunocytochemistry.

RESULTS

The PGE(2) production by IL-1beta-stimulated GFB was significantly upregulated by glycine. The effect of glycine on IL- 1beta-induced cell proliferation and PGE(2) production was concentration- dependent, reached a peak at 3 mM, and declined slowly at higher doses. The synthesis of PGE(2) by human GFB cultured in the absence of glycine was significantly inhibited by IL-10 and partially induced in cells cultured with glycine. Glycine had no effect on TNF-alpha-induced PGE(2) production. The IL-1beta-driven PGE(2) synthesis was blocked by indomethacin, a COX-1/COX-2 inhibitor, and by COX-2 inhibitor NS-398. The expression of COX-2 protein was slightly induced by glycine, more evidently by IL-1beta, and mostly enhanced by combined IL-1beta with glycine.

CONCLUSION

Since PGE(2) is a potent stimulator of bone resorption, and production of PGE(2) and COX-2 protein is augmented by glycine, our results strongly suggest that glycine may be involved in the pathogenesis of periodontitis.

Protection from fluorescein isothiocyanate-induced fibrosis in IL-13-deficient, but not IL-4-deficient, mice results from impaired collagen synthesis by fibroblasts

Intratracheal injection of FITC results in acute lung injury and progresses to fibrosis by day 21 postchallenge. In response to FITC, BALB/c mice produce IL-4 and IL-13 in the lung. To investigate whether IL-4 and/or IL-13 were important profibrotic mediators in this model, we examined the fibrotic response to FITC in mice that were genetically deficient in IL-4 (IL-4(-/-)), IL-13 (IL-13(-/-)), or IL-4 and IL-13 combined (IL-4/13(-/-)). Baseline levels of collagen were similar in all mice. In response to FITC, both BALB/c and IL-4(-/-) mice developed fibrosis, whereas the IL-13(-/-) and IL-4/13(-/-) mice were significantly protected, as measured by total lung collagen levels and histology. Total leukocyte recruitment to the lung was similar in all four strains of mice when measured on days 7, 14, and 21 post-FITC. BALB/c mice showed prominent eosinophilia on day 7 that was absent in IL-4(-/-), IL-13(-/-), and IL-4/13(-/-) mice, suggesting that eosinophilia is not necessary for development of a fibrotic response. There were no significant differences in the percentages of any other leukocytes analyzed between the genotypes. Similarly, protection in IL-13(-/-) mice was not associated with alterations in cytokine or eicosanoid profiles. Interestingly, TGF-beta1 production was not reduced in IL-13(-/-) mice. Analyses of fibroblasts isolated from the four genotypes demonstrated that although there were similar numbers of fibroblasts present in cultures of lung minces, fibroblasts from IL-13-deficient strains have reduced basal and stimulated levels of collagen production. IL-13Ralpha1 expression increases on fibroblasts during fibrotic responses in vivo, and IL-13 increases collagen synthesis in fibroblasts. Thus, IL-13 mediates its profibrotic actions through direct effects on fibroblast production of extracellular matrix.

Pronounced induction of testicular PGF2$alpha; and suppression of testosterone by cadmium?prevention by zinc

In order to investigate the effects of cadmium (Cd) on testicular prostaglandin F(2 alpha) (PGF(2 alpha)) production, adult male Sprague-Dawley rats were exposed to CdCl(2) by subcutaneous injections. Dose-response as well as temporal-response experiments were performed, and PGF(2 alpha) levels were determined by radioimmunoassay (RIA). The highest cadmium dose (10 micromol/kg) caused a dramatic elevation of testicular PGF(2 alpha), which was established to occur 48 h after exposure. At this point of time, cadmium-treated animals displayed PGF(2 alpha) levels 16.7 times higher than saline-injected controls. No significant differences were found with the lower doses used (1 and 5 micromol/kg). In addition, the influence of pre-treatment with zinc (Zn) was assessed. The very strong stimulatory effect on PGF(2 alpha) synthesis (22.3-fold) detected after exposure to 20 micromol/kg cadmium, was completely absent in the group given zinc (1 mmol/kg) prior to cadmium exposure. Plasma testosterone concentrations were determined in the three experiments, and all groups with strongly elevated PGF(2 alpha) levels showed drastically lowered concentrations of testosterone. Zinc pre-treatment abolished not only the cadmium-induced rise in PGF(2 alpha) but also the testosterone reduction. Additionally, cadmium was found to inhibit the expression of steroidogenic acute regulatory protein (StAR), which is responsible for the rate-limiting step in steroidogenesis. The present findings establish that cadmium can cause a strong induction of testicular PGF(2 alpha) production, which might help to explain the well-known antisteroidogenic effect of this heavy metal. Such an inhibitory effect could be due to reduced levels of StAR.

Downregulation of lipopolysaccharide-induced intercellular adhesion molecule-1 expression via EP2/EP4 receptors by prostaglandin E2 in human fibroblasts

In the present study, the effect of prostaglandin E2 (PGE2) on intercellular adhesion molecule-1 (ICAM-1) expression in human gingival fibroblasts (HGF) stimulated with lipopolysaccharides (LPS) was investigated. LPS were isolated from periodontopathic bacteria, Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) and Porphyromonas gingivalis (P. gingivalis), by the phenol-water method and Escherichia coli (E. coli) LPS was used as a control. PGE2 significantly inhibited A. actinomycetemcomitans-, P. gingivalis- and E. coli-LPS-induced ICAM-1 expression. Next, of four PGE2 receptor subtypes (EP1, EP2, EP3 and EP4), we examined which subtype(s) was involved in inhibition of LPS-elicited ICAM-1 expression by PGE2. Eleven-deoxy-PGE1, a selective EP2/EP4 agonist, and butaprost, a selective EP2 agonist, attenuated A. actinomycetemcomitans-, P. gingivalis- and E. coli-LPS-elicited ICAM-1 expression, although butaprost was less potent than PGE2 and 11-deoxy-PGE1. Sulprostone, an EP1/EP3 agonist, and ONO-AP-324, an EP3 agonist, was inert to the LPS-elicited ICAM-1 expression. Furthermore, dibutyryl cAMP, a cAMP analogue, and forskolin, an adenylate cyclase activator, downregulated A. actinomycetemcomitans-, P. gingivalis- and E. coli-LPS-elicited ICAM-1 expression in HGF. Our data suggest that PGE2 downregulates A. actinomycetemcomitans- and P. gingivalis-LPS-induced ICAM-1 expression in HGF, via EP2/EP4 receptors by cAMP-dependent signaling pathways. The cAMP-elevating agents such as EP2/EP4 receptor activators may serve to control inflammatory and immune responses in periodontal disease.

Prostaglandin E2 receptors of the EP2 and EP4 subtypes downregulate tumor necrosis factor alpha-induced intercellular adhesion molecule-1 expression in human gingival fibroblasts

Prostaglandin E2 (PGE2) exerts its biological actions via EP receptors, which are divided into 4 subtypes of EP1, EP2, EP3 and EP4. In the present study, we investigated whether PGE2 regulated intercellular adhesion molecule-1 (ICAM-1) expression in human gingival fibroblasts (HGF) stimulated with tumor necrosis factor-alpha (TNF alpha) and if so, which subtype(s) of PGE2 receptors was involved. Exogenous addition of PGE2 to HGF inhibited ICAM-1 expression elicited by TNF alpha in a concentration-dependent manner. Treatment of HGF with indomethacin, a cyclo-oxygenase inhibitor, had no effect on TNF alpha-elicited ICAM-1 expression, although indomethacin completely inhibited PGE2 production enhanced by TNF alpha. Next, we examined which subtype(s) of the 4 EP receptors modulated the ICAM-1 expression elicited by TNF alpha, using subtype-specific agonists and antagonists. 11-deoxy-PGE1, a selective EP2/EP4 agonist, inhibited TNF alpha-elicited ICAM-1 expression as potently as PGE2, while butaprost, a selective EP2 agonist, was somewhat less effective than PGE2. AH23848B, an EP4 antagonist, antagonized the inhibitory effect of TNF alpha-elicited ICAM-1 expression by PGE2. Sulprostone, an EP1/EP3 agonist, and ONO-AP-324, an EP3 agonist, were inert to TNF alpha-elicited ICAM-1 expression. As EP2 and EP4 receptors are linked to elevation of intracellular cyclic AMP (cAMP), the effect of dibutyryl cAMP and 8-bromo-cAMP, cAMP analogs, on TNF alpha-elicited ICAM-1 expression was examined. Both the agents downregulated ICAM-1 expression in TNF alpha-stimulated HGF. From these data, we suggest that PGE2 downregulates TNF alpha-induced ICAM-1 expression in HGF, via EP2 and EP4 receptors by cAMP-dependent signaling pathways, which may result in control of inflammatory and immunological responses in periodontal disease.

Prostaglandin E2 downregulates interferon-gamma-induced intercellular adhesion molecule-1 expression via EP2 receptors in human gingival fibroblasts

In the present study, the effect of prostaglandin E2 (PGE2) on intercellular adhesion molecule-1 (ICAM-1) expression in interferon-gamma (IFN-gamma)-stimulated human gingival fibroblasts (HGF) was investigated. Addition of PGE2 to HGF inhibited ICAM-1 expression elicited by IFN-gamma. As PGE2 elevated intercellular cyclic AMP (cAMP) levels in HGF in a dose-dependent fashion, the effect of dibutyryl cAMP and 8-bromo-cAMP, cAMP analogues, on IFN-gamma-elicited ICAM-1 expression was examined. Both the agents downregulated ICAM-1 expression in IFN-gamma-stimulated HGF. Next, we examined which subtype(s) of the four PGE2 receptor subtypes (EP1, EP2, EP3 and EP4) modulated the ICAM-1 expression elicited by IFN-gamma, using subtype-specific agonists or antagonists. An EP2/EP4 agonist, 11-deoxy-PGE1, attenuated IFN-gamma-elicited ICAM-1 expression in a concentration-dependent manner. A specific EP4 antagonist, AH-23848B, showed no effect on inhibition of IFN-gamma-elicited ICAM-1 expression by PGE2 and 11-deoxy-PGE1. Butaprost, an EP2-selective agonist, mimicked inhibition of IFN-gamma-elicited ICAM-1 expression by 11-deoxy-PGE1. An EP3 agonist, ONO-AP-324, was inert with respect to IFN-gamma-elicited ICAM-1 expression. Sulprostone, an EP1/EP3 agonist, showed stimulatory effect on ICAM-1 expression elicited by IFN-gamma. From these results, we suggest that PGE2 downregulates IFN-gamma-induced ICAM-1 expression in HGF, primarily via EP2 receptors by cAMP-dependent signaling pathways.