Effect of Taraxaci Herba on Bone Loss in an OVX-Induced Model through the Regulation of Osteoclast Differentiation.

Bone is a dynamic tissue that maintains homeostasis with a balance of osteoclasts for bone resorption and osteoblasts for bone formation. Women are deficient in estrogen after menopause, which promotes bone resorption due to excessive activity of osteoclasts, leading to osteoporosis. TH (also known as dandelion) is native to warm regions and has traditionally been used to treat gynecological diseases and inflammation. Menopause is a major cause of osteoporosis as it causes abnormal activity of osteoclasts, and various studies have shown that anti-inflammatory drugs have the potential to treat osteoporosis. We analyzed the effect of TH on osteoclast differentiation and the relevant mechanisms using RANKL. After administration of TH in a menopause-like rat model in which ovariectomy of the was rats carried out, changes in bone microstructure were analyzed via micro-CT, and the antiosteoporosis effect of TH was verified by a histological analysis. In addition, the pharmacological effects of TH in an animal model of osteoporosis were compared and analyzed with osteoporosis medications (17ß-estradiol (E2) and alendronate (ALN)). TH significantly inhibited the initial osteoclast differentiation via the NFATc1/c-Fos mechanism. In addition, bone density in the femur of osteoporotic rats was increased, and the expression of osteoclast-related factors in the serum and tissues was controlled. The results of this study provide objective evidence of the inhibitory effect of TH on osteoclastogenesis and OVX-induced bone loss.

Solanum nigrum Line inhibits osteoclast differentiation and suppresses bone mineral density reduction in the ovariectomy­induced osteoporosis model.

Bone homeostasis is maintained by osteoclasts that absorb bone and osteoblasts that form bone tissue. Menopausal osteoporosis is a disease associated with aging and hormonal changes due to menopause causing abnormal activation of osteoclasts, resulting in a decrease in bone density. Existing treatments for osteoporosis have been reported to have serious side effects, such as jawbone necrosis and breast and uterine cancer; therefore, their use by patients is decreasing, whilst studies focusing on alternative treatments are increasingly popular. Solanum nigrum Line (SL) has been used as a medicinal plant that possesses several pharmacological effects, such as anti­inflammatory and hepatotoxic protective effects. To the best of our knowledge, however, its effects on osteoporosis and osteoclasts have not been demonstrated previously. In the present study, the anti­osteoporotic effect of SL was investigated using a postmenopausal model of osteoporosis in which Sprague­Dawley rat ovaries were extracted. In addition, the inhibitory effects on osteoclast differentiation and function of SL was confirmed using an osteoclast model treated with receptor activator of NF­κB ligand (RANKL) on murine RAW 264.7 macrophages. In vivo experiments showed that SL reduced the decrease in bone mineral density and improved changes in the morphological index of bone microstructure, such as trabecular number and separation. In addition, the number of tartrate resistant acid phosphatase­positive cells in the femur and the expression levels of nuclear factor of activated T­cells cytoplasmic 1 (NFATc1) and cathepsin K protein were inhibited. In vitro, SL suppressed RANKL­induced osteoclast differentiation and bone resorption ability; this was mediated by NFATc1/c­Fos, a key transcription factor involved in osteoclast differentiation, ultimately inhibiting expression of various osteoclast­associated genes. These experimental results show that SL may be an alternative treatment for osteoporosis caused by abnormal activation of osteoclasts in the future.

TBK1-targeted suppression of TRIF-dependent signaling pathway of Toll-like receptors by helenalin.

AIMS: The purpose of this study was to evaluate the therapeutic potential of the helenalin in Toll-like receptor (TLR) signaling pathways. MAIN METHODS: RAW264.7 cells were transfected with a NF-κB, IFNß PRDIII-I, or IP-10 luciferase plasmid and then luciferase enzyme activities were determined by luciferase assay. The expression of iNOS, COX-2, and IP-10 and phosphorylation of IRF3 were determined by Western blotting. The levels of IP-10 were determined with culture medium by using IP-10 ELISA kit. TBK1 kinase activity was determined by MBP assay kit. KEY FINDINGS: Helenalin inhibited transcription factor NF-κB and IRF3 activation, which was induced by TLR agonists as well as its target genes, such as COX-2, iNOS, and IP-10. Helenalin attenuated ligand-independent activation of NF-κB induced by MyD88, IKKß, and p65, and IRF3 induced by TRIF, TBK1, or IRF3. Furthermore, helenalin inhibited TBK1 kinase activity in vitro. SIGNIFICANCE: TLRs are primary sensors that detect a wide variety of microbial components and play an important role in the induction of innate immune. To evaluate the therapeutic potential of helenalin, we examined its effect on signal transduction via the TLR signaling pathways. Our results suggest that beneficial effects of helenalin on chronic inflammatory diseases are mediated through modulation of TLR signaling pathways by targeting TBK1.

Isobavachalcone suppresses expression of inducible nitric oxide synthase induced by Toll-like receptor agonists.

Toll-like receptors (TLRs) play an important role by recognizing many pathogen-associated molecular patterns and inducing innate immunity. Dysregulated activation of TLR signaling pathways induces the activation of various transcription factors such as nuclear factor-κB, leading to the induction of pro-inflammatory gene products such as inducible nitric oxide synthase (iNOS). The present study investigated the effect of isobavachalcone (IBC), a natural chalcone component of Angelica keiskei, on inflammation by modulating iNOS expression induced by TLR agonists in murine macrophages. IBC suppressed iNOS expression induced by macrophage-activating lipopeptide 2-kDa, polyriboinosinic polyribocytidylic acid, or lipopolysaccharide. These results indicate the potential of IBC as a potent anti-inflammatory drug.

Suppression of TRIF-dependent signaling pathway of toll-like receptors by allyl isothiocyanate in RAW 264.7 macrophages.

Toll-like receptors (TLR) play a significant role in the induction of innate immune responses that are essential for host defense against invading microbial pathogens. In general, TLRs have two major downstream signaling pathways: myeloid differential factor 88 (MyD88)-dependent and toll-interleukin-1 receptor domain-containing adapter inducing interferon-ß (TRIF)-dependent pathways. Allyl isothiocyanate (AITC) found in cruciferous vegetables has an effect on treatment of many chronic diseases. However, the exact molecular targets of AITC are still unidentified. Here, it was investigated whether AITC can modulate TLR signaling pathways and what is the molecular target of AITC in TLRs signaling pathways. AITC suppressed the activation of nuclear factor-κB by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly[I:C]), but not by macrophage-activating lipopeptide of 2kDa (MALP-2) or cytosine-phosphate-guanine dinucleotide (CpG DNA). AITC also suppressed the activation of interferon regulatory factor 3 (IRF3) and the expression of interferon inducible protein-10 (IP-10) induced by LPS or poly[I:C]. These results suggest that AITC can modulate TRIF-dependent signaling pathways of TLRs leading to decreased inflammatory gene expression.

Suppression of the TRIF-dependent signaling pathway of toll-like receptors by (E)-isopropyl 4-oxo-4-(2-oxopyrrolidin-1-yl)-2-butenoate.

Toll-like receptors (TLRs) are pattern recognition receptors that recognize molecular structures derived from microbes and initiate innate immunity. TLRs have two downstream signaling pathways, the MyD88- and TRIF-dependent pathways. Dysregulated activation of TLRs is closely linked to increased risk of many chronic diseases. Previously, we synthesized fumaryl pyrrolidinone, (E)-isopropyl 4-oxo-4-(2-oxopyrrolidin-1- yl)-2-butenoate (IPOP), which contains a fumaric acid isopropyl ester and pyrrolidinone, and demonstrated that it inhibits the activation of nuclear factor kappa B by inhibiting the MyD88-dependent pathway of TLRs. However, the effect of IPOP on the TRIF-dependent pathway remains unknown. Here, we report the effect of IPOP on signal transduction via the TRIF-dependent pathway of TLRs. IPOP inhibited lipopolysaccharide- or polyinosinic-polycytidylic acid-induced interferon regulatory factor 3 activation, as well as interferon- inducible genes such as interferon inducible protein-10. These results suggest that IPOP can modulate the TRIF-dependent signaling pathway of TLRs, leading to decreased inflammatory gene expression.

Parthenolide inhibits TRIF-dependent signaling pathway of Toll-like receptors in RAW264.7 macrophages.

Toll-like receptors (TLRs) play an important role in induction of innate immune responses for host defense against invading microbial pathogens. Microbial component engagement of TLRs can trigger the activation of myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter inducing interferon-ß (TRIF)-dependent downstream signaling pathways. Parthenolide, an active ingredient of feverfew (Tanacetum parthenium), has been used for centuries to treat many chronic diseases. Parthenolide inhibits the MyD88-dependent pathway by inhibiting the activity of inhibitor-κB kinase. However, it is not known whether parthenolide inhibits the TRIF-dependent pathway. To evaluate the therapeutic potential of parthenolide, its effect on signal transduction via the TRIF-dependent pathway of TLRs induced by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly [I:C]) was examined. Parthenolide inhibited nuclear factor-κB and interferon regulatory factor 3 activation induced by LPS or poly[I:C], and the LPS-induced phosphorylation of interferon regulatory factor 3 as well as interferon-inducible genes such as interferon inducible protein-10. These results suggest that parthenolide can modulate TRIF-dependent signaling pathways of TLRs, and may be the basis of effective therapeutics for chronic inflammatory diseases.