Blockade of the p38 mitogen-activated protein kinase pathway inhibits inducible nitric oxide synthase and interleukin-6 expression in MC3T3E-1 osteoblasts

Functional role of skeletal muscle-derived interleukin-6 and its effects on lipid metabolism

The detrimental impact of obesity on human health is increasingly evident with the rise in obesity-related diseases. Skeletal muscle, the crucial organ responsible for energy balance metabolism, plays a significant role as a secretory organ by releasing various myokines. Among these myokines, interleukin 6 (IL-6) is closely associated with skeletal muscle contraction. IL-6 triggers the process of lipolysis by mobilizing energy-storing adipose tissue, thereby providing energy for physical exercise. This phenomenon also elucidates the health benefits of regular exercise. However, skeletal muscle and adipose tissue maintain a constant interaction, both directly and indirectly. Direct interaction occurs through the accumulation of excess fat within skeletal muscle, known as ectopic fat deposition. Indirect interaction takes place when adipose tissue is mobilized to supply the energy for skeletal muscle during exercise. Consequently, maintaining a functional balance between skeletal muscle and adipose tissue becomes paramount in regulating energy metabolism and promoting overall health. IL-6, as a representative cytokine, participates in various inflammatory responses, including non-classical inflammatory responses such as adipogenesis. Skeletal muscle influences adipogenesis through paracrine mechanisms, primarily by secreting IL-6. In this research paper, we aim to review the role of skeletal muscle-derived IL-6 in lipid metabolism and other physiological activities, such as insulin resistance and glucose tolerance. By doing so, we provide valuable insights into the regulatory function of skeletal muscle-derived myokines in lipid metabolism.

Immunosuppressive potential of astemizole against LPS activated T cell proliferation and cytokine secretion in RAW macrophages, zebrafish larvae and mouse splenocytes by modulating MAPK signaling pathway

In this study, the immunomodulatory effects of astemizole (AST) against lipopolysaccharide (LPS) mediated T cell proliferation and induction of inflammation in RAW macrophages (in vitro), and zebrafish larvae (in vivo) were determined. AST significantly suppressed the phagocytic activity of macrophages (3.303 ± 0.115) and inhibited lysosomal enzyme secretion (13.27 ± 2.52) induced by LPS (100 ng/ml). Moreover, AST subdued the morphological deformities such as yolk sac edema (YSE) and spinal curvature curving (SC) by inhibiting ROS generation in zebrafish larvae 24 h after microinjection of LPS (0.5 mg/ml). AST was also shown to inhibit the production of the major cytokines TNF-α (150.8 ± 0.6), IL-1β (276.5 ± 1.6), and PGE₂ (194.6 ± 0.6) pg/ml in RAW macrophages. It also subdued the ROS induced iNOS and COX-2 generated in response to LPS mediated immune dysfunctions in zebrafish larvae. These results suggested the immunosuppression effect of AST. Furthermore, induction of immune-suppression due to AST resulted in significant down-regulation of innate immunity directed by MAPK (p38, ERK and JNK), which was found to be associated with decreased production of acute inflammatory mediators both in vitro and in vivo. To confirm its activity, splenocytes were prepared using BALB/c mice and a mitogen activated splenocyte proliferation assay was also performed. Our findings suggest that AST has the ability to inhibit T cell proliferation and cytokine secretion both in vitro and in vivo by interfering with MAPK signaling pathway. Taken together, our results showed the potential of AST as a countermeasure to immune dysfunction and suggest its use as immunosuppressant compound in inflammatory disease.

Role of testis-specific high-mobility-group protein in transcriptional regulation of inducible nitric oxide synthase expression in the liver of endotoxic shock mice

Inducible nitric oxide synthase (iNOS) plays a central role in tissue damage during endotoxic shock. However, the underlying mechanisms that control transcription of iNOS are not completely defined. A screening strategy with DNA pull-down technology and two-dimensional difference in gel electrophorcsis (2D-DIGE) analysis was used to identify regulators that interact with the iNOS promoter. We found 14 proteins that bind to the iNOS promoter in the liver of endotoxic shock mice. After matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis, one of these proteins was identified as testis-specific high-mobility-group protein (tsHMG), an alternative splicing isoform encoded by the mitochondrial transcription factor A gene. We identified the binding sites of tsHMG on the iNOS promoter using a LiquiChip system, and further confirmed interactions between tsHMG and iNOS by RT-PCR, western blotting and immunofluorescence. Functional analysis by over-expression and RNA interference of tsHMG revealed that tsHMG regulates lipopolysaccharide-stimulated iNOS expression. These results indicate that tsHMG participates in modulation of iNOS expression in the early stage of endotoxic shock.

Gastrodin ameliorates anxiety-like behaviors and inhibits IL-1beta level and p38 MAPK phosphorylation of hippocampus in the rat model of posttraumatic stress disorder

Gastrodin, a main constituent of a Chinese herbal medicine, has been shown to be effective in treating various mood disorders. The purpose of the present study was to determine whether gastrodin could ameliorate stress-associated behavior in a rat model of enhanced single prolonged stress (ESPS)-induced posttraumatic stress disorder (PTSD). Following ESPS, rats were administered orally with gastrodin (50, 100, or 200 mg/kg daily) or vehicle for 2 weeks. Animals were then tested in the open field and elevated plus-maze, and the levels of IL-6 and IL-1beta, the expression of iNOS, p38 and phospho-p38 (p-p38) in hippocampus were also tested. ESPS exposure resulted in pronounced anxiety-like behavior, elevated IL-6 and IL-1beta levels, and the higher expression of iNOS and p-p38 in hippocampus. However, repeated treatment with gastrodin, particularly at higher doses, reversed the aforementioned changes, including anxiety-like behavior, levels of IL-6 and IL-1beta, and the expression of iNOS and the p38 MAPK phosphorylation. These results indicate that gastrodin possesses anxiolytic effect and may be an effective herbal preparation for the treatment of PTSD.

Antitumor effect of paclitaxel is mediated by inhibition of myeloid-derived suppressor cells and chronic inflammation in the spontaneous melanoma model

The antitumor effects of paclitaxel are generally attributed to the suppression of microtubule dynamics resulting in defects in cell division. New data demonstrated that in ultralow noncytotoxic concentrations, paclitaxel modulated in immune cells in vitro the activity of small Rho GTPases, the key regulators of intracellular actin dynamics. However, the immunomodulatory properties of paclitaxel in vivo have not been evaluated. In this study, using the ret transgenic murine melanoma model, which mimics human cutaneous melanoma, we tested effects of ultralow noncytotoxic dose paclitaxel on functions of myeloid-derived suppressor cells (MDSCs), chronic inflammatory mediators, and T cell activities in the tumor microenvironment in vivo. Administration of paclitaxel significantly decreased accumulation and immunosuppressive activities of tumor-infiltrating MDSCs without alterations of the bone marrow hematopoiesis. This was associated with the inhibition of p38 MAPK activity, TNF-α and production, and S100A9 expression in MDSCs. The production of mediators of chronic inflammation in the tumor milieu also was diminished. Importantly, reduced tumor burden and increased animal survival upon paclitaxel application was mediated by the restoration of CD8 T cell effector functions. We suggest that the ability of paclitaxel in a noncytotoxic dose to block the immunosuppressive potential of MDSCs in vivo represents a new therapeutic strategy to downregulate immunosuppression and chronic inflammation in the tumor microenvironment for enhancing the efficacy of concomitant anticancer therapies.

Grape-seed proanthocyanidin extract as suppressors of bone destruction in inflammatory autoimmune arthritis

Chronic autoimmune inflammation, which is commonly observed in rheumatoid arthritis (RA), disrupts the delicate balance between bone resorption and formation causing thedestruction of the bone and joints. We undertook this study to verify the effects of natural grape-seed proanthocyanidin extract (GSPE), an antioxidant, on chronic inflammation and bone destruction. GSPE administration ameliorated the arthritic symptoms of collagen-induced arthritis (CIA), which are representative of cartilage and bone destruction. GSPE treatment reduced the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and osteoclast activity and increased differentiation of mature osteoblasts. Receptor activator of NFκB ligand expression in fibroblasts from RA patients was abrogated with GSPE treatment. GSPE blocked human peripheral blood mononuclear cell-derived osteoclastogenesis and acted as an antioxidant. GSPE improved the arthritic manifestations of CIA mice by simultaneously suppressing osteoclast differentiation and promoting osteoblast differentiation. Our results suggest that GSPE may be beneficial for the treatment of inflammation-associated bone destruction.

The Role of Nitric Oxide on the Proliferation of a Human Osteoblast Cell Line Stimulated With Hydroxyapatite

The aim of the present study was to test the hypothesis that the proliferation of a human osteoblast cell line (HOS cells) stimulated with hydroxyapatite (HA) may be regulated by nitric oxide (NO). The cells were cultured on the surface of HA. Medium or cells alone were used as controls. L-arginine, D-arginine, 7-NI (an nNOS inhibitor), L-NIL (an iNOS inhibitor), L-NIO (an eNOS inhibitor) or carboxy PTIO, a NO scavenger, was added in the HA-exposed cell cultures. The cells were also precoated with anti-human integrin αV antibody. The levels of nitrite were determined spectrophotometrically. Cell proliferation was assessed by colorimetric assay. The results showed increased nitrite production and cell proliferation by HA-stimulated HOS cells up to day 3 of cultures. Anti-integrin αV antibody, L-NIO, or carboxy PTIO suppressed, but L-arginine enhanced, nitrite production and cell proliferation of HA-stimulated HOS cells. The results of the present study suggest, therefore, that interaction between HA and HOS cell surface integrin αV molecule may activate eNOS to catalyze NO production which, in turn, may regulate the cell proliferation in an autocrine fashion.

Role of Sandhika: A Polyherbal Formulation on MC3T3-E1 Osteoblast-like Cells

Sandhika is a polyherbal formulation, (water soluble fraction of Commiphora mukul, Boswellia serrata, Semecarpus anacardium and Strychnos nux vomica), which has been in clinical use in India for last 20 years. Its modified formulation BHUx has shown specific inhibition of cyclooxygenase (COX)-2 and lipoxygenase (LOX)-15 and has prevented diet-induced atherosclerosis in rabbits. In order to explore the possibility of the use of Sandhika for the management of osteoporosis, we have examined its influence on MC3T3-E1 osteoblast-like cells in presence of lipopolysaccharide (1 microg/ml) in terms of calcium nodule formation and alkaline phosphatase activity. MC3T3-E1 osteoblast-like cells (80% confluence in 6-well plates) were treated with water extract of Sandhika, for 10 days, in the concentration range of 0.5 to 16 mg/ml final concentration, in presence of LPS. Media was changed on every third day and culture supernatant was collected after every change to assess the alkaline phosphatase activity and on the tenth day, cells were washed and stained with "Alizarin S" for visualization of calcium nodules by using Meta Morph software (Universal Imaging, Downingtown, PA). The results showed significant enhancement in calcium nodule formation in the dose dependent manner up to 2 mg/ml, followed by gradual decrease at higher concentrations. This change was accompanied with the increase in the alkaline phosphatase activity in these plates, indicating a potential anabolic effect of this polyherbal formulation on osteoblast-like cells under inflammatory conditions induced by LPS.

Prothymosin α Lacking the Nuclear Localization Signal as an Effective Gene Therapeutic Strategy in Collagen-Induced Arthritis

Prothymosin alpha (ProT) is regulated by c-Myc, an oncoprotein overexpressed in synovium of rheumatoid arthritis, and is associated with cell proliferation. However, ProT also exerts immunomodulatory activities. The growth-promoting activity of ProT can be abolished by deleting its nuclear localization signal (NLS). In this study, we showed that AdProTDeltaNLS, an adenoviral vector encoding ProT lacking the NLS, did not enhance the proliferation of synovial fibroblasts. AdProTDeltaNLS treatment abolished the up-regulation of the MIP-1alpha promoter activity induced by TNF-alpha in synovial fibroblasts. AdProTDeltaNLS suppressed macrophage chemotaxis and reduced macrophage infiltration into the ankle joints in rats with collagen-induced arthritis (CIA). Neutralization test confirmed the involvement of MIP-1alpha in macrophage chemotaxis. Administration of AdProTDeltaNLS reduced the severity of CIA in the clinical, radiographic, and histological aspects. The levels of TNF-alpha (mean +/- SEM, 1261.9 +/- 107.9 vs 2880.1 +/- 561.4 pg/mg total protein; p < 0.05), IL-1beta (56.8 +/- 8.0 vs 109.2 +/- 4.9 pg/mg total protein; p < 0.01), and MIP-1alpha (41.7 +/- 3.6 vs 55.2 +/- 1.1 pg/mg total protein; p < 0.05) in the ankle joints were lower in the AdProTDeltaNLS-treated rats with CIA than those in their control counterparts. In the AdProTDeltaNLS-treated ankle joints, matrix metalloproteinase-9 expression was decreased by 40% and infiltrating macrophages reduced by 50%. Our results demonstrate that intra-articular delivery of AdProTDeltaNLS significantly ameliorated the clinical course of CIA in rats. This study is the first to suggest that ProT lacking the NLS may have therapeutic potential for the management of rheumatoid arthritis.

p38 MAPK regulates IL-1beta induced IL-6 expression through mRNA stability in osteoblasts

Osteoblast-derived IL-6 functions in coupled bone turnover by supporting osteoclastogenesis favoring bone resorption instead of bone deposition. Gene regulation of IL-6 is complex occurring both at transcription and post-transcription levels. The focus of this paper is at the level of mRNA stability, which is important in IL-6 gene regulation. Using the MC3T3-E1 as an osteoblastic model, IL-6 secretion was dose dependently decreased by SB203580, a p38 MAPK inhibitor. Steady state IL-6 mRNA was decreased with SB203580 (2 microM) ca. 85% when stimulated by IL-1beta (1-5 ng/ml). These effects require de novo protein synthesis as they were inhibited by cycloheximide. p38 MAPK had minor effects on proximal IL-6 promoter activity in reporter gene assays. A more significant effect on IL-6 mRNA stability was observed in the presence of SB203580. Western blot analysis confirmed that SB203580 inhibited p38 MAP kinase, in response to IL-1beta in a dose dependent manner in MC3T3-E1 cells. Stably transfected MC3T3-E1 reporter cell lines (MC6) containing green fluorescent protein (GFP) with the 3'untranslated region of IL-6 were constructed. Results indicated that IL-1beta, TNFalpha, LPS but not parathyroid hormone (PTH) could increase GFP expression of these reporter cell lines. Endogenous IL-6 and reporter gene eGFP-IL-6 3'UTR mRNA was regulated by p38 in MC6 cells. In addition, transient transfection of IL-6 3'UTR reporter cells with immediate upstream MAP kinase kinase-3 and -6 increased GFP expression compared to mock transfected controls. These results indicate that p38 MAPK regulates IL-1beta-stimulated IL-6 at a post transcriptional mechanism and one of the primary targets of IL-6 gene regulation is the 3'UTR of IL-6.

Carbon monoxide and nitric oxide protect against tumor necrosis factor-alpha-induced apoptosis in osteoblasts: HO-1 is necessary to mediate the protection

BACKGROUND

Carbon monoxide (CO) and nitric oxide (NO) each have unique roles for various inflammatory states, including inflammatory bone resorption. Although it is known that NO can induce the expression of the cytoprotective enzyme HO-1, there is no information as to whether the protective effect of CO requires NO production or whether CO must induce the expression of HO-1 to exert its functional effects.

METHODS

Murine osteoblast cells, MC3T3E1 osteoblasts, were cultured for CO and NO-associated HO-1 experiments and were transfected with pcDNA 3, pcDNA 3-HO-1, control siRNA or HO-1 siRNA using Nucleofector. For cell death measurement, MTT and annexin V assays were used. We performed Western blotting to check the expressions of HO-1 and iNOs and measured the HO-1 enzyme activity. We also measured the amounts of nitrite and nitrate using Griess reagents.

RESULTS

The increased expression of HO-1 is required for the protective effect of NO and a single treatment of CO can increase the expression of HO-1, and this is also important for the protective effect of CO in MC3T3E1 osteoblasts. CO as well as NO attenuates the TNF-alpha-induced apoptosis in osteoblasts. The anti-apoptotic effect of CO or NO is not mediated by cGMP, and CO has no effect on the release of NO. The inhibition of HO-1 with using the HO-1 inhibitor ZnPP or HO-1 siRNA resulted in a striking increase of apoptosis in the CO/TNF-alpha-treated cells. Furthermore, HO-1 overexpression showed resistance against the TNF-alpha-induced cytotoxicity in the MC3T3E1 osteoblasts.

CONCLUSIONS

There is a need for HO-1 expression to mediate the protection provided by exogenous CO or NO in osteoblasts.

MAP kinases differentially regulate the expression of macrophage hyperactivity after thermal injury

Thermal injury increases the capacity of macrophages (Mphi) to produce various inflammatory mediators, (i.e., Mphi hyperactivity), which is believed to be involved in the development of subsequent immunosuppression, sepsis, and multiple organ failure. The signal transduction pathways involved in the expression of Mphi hyperactivity post-burn, however, remain to be clearly elucidated. To study this C57BL/6 female mice were subjected to a 25% TBSA burn and splenic Mphis were isolated 7 days later. LPS-stimulated inflammatory mediator production and MAPK expression (P38 ERK 1/2 and JNK) were determined. Burn injury increased LPS-induced P38 MAPK, suppressed JNK activation and ERK 1/2 activation was unaltered. These changes in MAPK activation were paralleled by the increased production of PGE(2), TNF-alpha, IL-1beta, IL-6, and IL-10. Differential sensitivity to the inhibition of the MAPK pathways was observed with regard to the mediator evaluated and the presence or absence of burn injury. In general cytokine production in the burn group was in part resistant to the inhibition of a single MAPK pathway as compared with shams. Thus, burn injury increases cross-talk between the MAPKs pathways, suggesting that alterations MAPK activation and signal transduction contribute to the development Mphi hyperactivity post-injury.

Coal-induced interleukin-6 gene expression is mediated through ERKs and p38 MAPK pathways

In the present study, we have tested the ability of coal dust to stimulate kinase phosphorylation of activator protein-1 (AP-1) signal transduction pathways and production of interleukin-6 (IL-6) in both mouse epidermal JB6 and human lung epithelial A549 cells. Seven coal samples from three coalmine regions of Pennsylvania (PA), West Virginia (WV), and Utah (UT) with high, medium, and low prevalence of coal workers' pneumoconiosis (CWP), respectively, were investigated. Results from the present study indicate that three PA coals stimulated the mitogen-activated protein kinase (MAPK) family of extracellular signal-regulated kinases (ERKs) and p38 MAPK, but not c-Jun-NH2-terminal kinases (JNKs) in human lung A549 cells. The effects of three UT coals on the kinase phosphorylation were less as compared to those of the PA coals. Coal dusts from three coalmine regions induced IL-6 in a dose-dependent manner in both JB6 and A549 cells. Interestingly, levels of IL-6 in both cells treated with coals from three coalmine regions correlated well with CWP prevalence from that region. To assess the role of AP-1 pathways in coal-mediated transcriptional activation of IL-6, various inhibitors were used in cells treated with one PA coal, which induced a maximal response. It was found that the increase in IL-6 protein and mRNA by the PA coal was completely eliminated by the pretreatment of both cell types with PD98059, a specific MEK1 inhibitor, and SB202190, a p38 kinase inhibitor. Our results indicate that coal dust can stimulate IL-6 release from mouse epidermal JB6 cells and human lung epithelial A549 cells, and the coal-induced IL-6 increase may involve ERKs and p38 MAPK pathways.

Tumor necrosis factor-alpha induces interleukin-6 production via extracellular-regulated kinase 1 activation in breast cancer cells

Interleukin-6 (IL-6) and interleukin-11 (IL-11) are frequently produced by breast cancer cells. These interleukins promote osteoclast formation and may mediate osteolysis at the site of breast cancer bone metastases. Transforming growth factor-beta (TGF-beta), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) up-regulate IL-6 and IL-11 production in a cytokine-dependent fashion in breast cancer cells, but very little is known about their intracellular signaling pathways in breast cancer cells. To study TGF-beta, TNF-alpha and IL-1beta regulation of IL-6 and IL-11 production in human MDA-MB-231 breast cancer cells, we established single cell clones stably expressing dominant negative (DN) forms of the mitogen-activated protein kinases p38 (p38/AF) or ERK1 (ERK1K71R). We show here, that while basal, TGF-beta and IL-1beta induced IL-6 production was similar in parental cells and in pcDNA3 control, ERK1K71R and p38/AF clones, TNF-alpha induced IL-6 production was blunted in the ERK1K71R clones. TGF-beta and IL-1beta, but not TNF-alpha, induced IL-11 production in parental MDA-MB-231 cells. Similar findings were detected in clones stably expressing p38/AF and ERK1K71R, which did not change basal IL-11 production either. In conclusion, TNF-alpha induced IL-6 production is mediated via ERK1 activation in MDA-MB-231 cells. These observations may be helpful in designing new anti-osteolytic therapies.

Muscle-derived interleukin-6: mechanisms for activation and possible biological roles

It has recently been demonstrated that the marked increase in the systemic concentration of cytokine interleukin-6 (IL-6) seen with exercise originates from the contracting limb and that skeletal muscle cells per se are the likely source of the production. This review summarizes the possible mechanisms for activation and biological consequences of muscle-derived IL-6. It appears that intramuscular IL-6 is stimulated by complex signaling cascades initiated by both calcium (Ca2+) -dependent and -independent stimuli. It also seems likely that skeletal muscle produces IL-6 to aid in maintaining metabolic homeostasis during periods of altered metabolic demand such as muscular exercise or insulin stimulation. It may do so via local and/or systemic effects. This review also explores the efficacy that IL-6 may be used as a therapeutic drug in treating metabolic disorders such as obesity, type 2 diabetes, and atherosclerosis.