Lipoxygenase metabolites are mediators of PTH-dependent human osteoblast growth

Effects of inhibition of 5-lipoxygenase and 12-lipoxygenase pathways on skeletal muscle fiber regeneration

We investigated the effect of inhibition of 5-lipoxigenase (LOX) and 12-LOX pathways on the regeneration of skeletal muscle fibers after injury induced by a myotoxin (MTX) phospholipase A₂ from snake venom in an in vivo experimental model. Gastrocnemius muscles of mice injected with MTX presented an increase in 5-LOX protein expression, while 12-LOX was found to be a constitutive protein of skeletal muscle. Animals that received oral treatments with 5-LOX inhibitor MK886 or 12-LOX inhibitor baicalein 30 min and 48 h after MTX-induced muscle injury showed a reduction in the inflammatory process characterized by a significant decrease of cell influx and injured fibers in the degenerative phase (6 and 24 h after injury). In the beginning of the regeneration process (3 days), mice that received MK886 showed fewer new basophilic fibers, suggesting fewer proliferative events and myogenic cell fusion. Furthermore, in the progression of tissue regeneration (14-21 days), the mice treated with 5-LOX inhibitor presented a lower quantity of central nucleus fibers and small-caliber fibers, culminating in a muscle that is more resistant to the stimulus of fatigue during muscle regeneration with a predominance of slow fibers. In contrast, animals early treated with the 12-LOX inhibitor presented functional fibers with higher diameters, less resistant to fatigue and predominance of fast heavy-chain myosin fibers as observed in control animals. These effects were accompanied by an earlier expression of myogenic factor MyoD. Our results suggest that both 5-LOX and 12-LOX pathways represent potential therapeutic targets for muscle regeneration. It appears that inhibition of the 5-LOX pathway represses only the degenerative process by reducing tissue inflammation levels. Meanwhile, inhibition of the 12-LOX pathway also favors the anticipation of maturation and earlier recovery of muscle fiber activity function after injury.

Matrix stiffness regulates bone repair by modulating 12-lipoxygenase-mediated early inflammation

Lipid metabolism in macrophages has been increasingly emphasized in exerting an anti-inflammatory effect and accelerating fracture healing. 12-lipoxygenase (12-LOX) is expressed in several cell types, including macrophages, and oxidizes polyunsaturated fatty acids (PUFAs) to generate both pro- and anti-inflammatory lipid mediators, of which the n-3 PUFAs play an important part in tissue homeostasis/fibrosis. Although mechanical factor regulates the lipid metabolic axis of inflammatory cells, specifically matrix stiffness influences macrophages metabolic responses, little is known about how matrix stiffness affects the 12-LOX-mediated early inflammation in bone repair. In the present study, demineralized bone matrix (DBM) scaffolds with different matrix stiffness were constructed by controlling the duration of decalcification (0 h (control), 1 h (high), 12 h (medium), and 5 d (low)) to repair the defected rat skull. The expression of inflammatory cytokines and macrophages polarization were analyzed. The lipid metabolites and lipid mediators' biosynthesis by matrix stiffness-regulated were further detected. The results showed that the low matrix stiffness could polarize macrophages into an anti-inflammatory phenotype, promote the expression of anti-inflammatory cytokines and specialized pro-resolving lipid mediators (SPMs) biosynthesis beneficial for the osteogenesis of mesenchymal stem cells (MSCs). After treated with ML355, the expression of anti-inflammatory cytokines/proteins and SPMs biosynthesis in macrophages cultured on low-matrix stiffness scaffolds were repressed, and there were almost no statistical differences among all groups. Findings from this study support that matrix stiffness regulates bone repair by modulating 12-LOX-mediated early inflammation, which suggest a direct mechanical impact of matrix stiffness on macrophages lipid metabolism and provide a new insight into the clinical application of SPMs for bone regeneration.

Inhibition of Lipoxygenases Showed No Benefit for the Musculoskeletal System in Estrogen Deficient Rats

BACKGROUND

In previous studies, we reported the beneficial impact of two lipoxygenase-inhibitors, Baicalein and Zileuton, on osteoporotic bone in a postmenopausal rat model. Whereas subcutaneous Baicalein predominantly improved cortical bone, Zileuton enhanced vertebral and femoral trabecular bone. In this study, we aimed to reveal whether the oral administration of Baicalein caused similar effects on bone and whether a combined administration of Baicalein and Zileuton could act synergistically to ameliorate the formerly reported effects in the musculoskeletal system.

METHODS

We treated ovariectomized (OVX) female Sprague-Dawley rats either with Baicalein (10mg/kg BW), Zileuton (10mg/kg BW) or a combination of both (each 10mg/kg BW) for 13 weeks and compared with untreated OVX and NON-OVX groups (n=12-16 rats per group). Lumbar vertebral bodies and femora were analyzed. Tibiae were osteotomized, plate-stabilized (at week 8 after OVX) and likewise analyzed by biomechanical, histological, micro-computed tomographical and ashing tests. The skeletal muscle structure was analyzed.

RESULTS

Oral administration of Baicalein did not confirm the reported favorable cortical effects in neither vertebra nor femur. Zileuton showed a beneficial effect on trabecular vertebra, while the femur was negatively affected. Callus formation was enhanced by all treatments; however, its density and biomechanical properties were unaltered. Lipoxygenase inhibition did not show a beneficial effect on skeletal muscle. The combination therapy did not ameliorate OVX-induced osteoporosis but induced even more bone loss.

CONCLUSIONS

The preventive anti-osteoporotic treatments with two lipoxygenase inhibitors applied either alone or in combination showed no benefit for the musculoskeletal system in estrogen deficient rats.

Effect of the lipoxygenase inhibitor baicalein on bone tissue and bone healing in ovariectomized rats

BACKGROUND

Osteoporosis is one of the world's major medical burdens in the twenty-first century. Pharmaceutical intervention currently focusses on decelerating bone loss, but phytochemicals such as baicalein, which is a lipoxygenase inhibitor, may rescue bone loss. Studies evaluating the effect of baicalein in vivo are rare.

METHODS

We administered baicalein to sixty-one three-month-old female Sprague-Dawley rats. They were divided into five groups, four of which were ovariectomized (OVX) and one non-ovariectomized (NON-OVX). Eight weeks after ovariectomy, bilateral tibial osteotomy with plate osteosynthesis was performed and bone formation quantified. Baicalein was administered subcutaneously using three doses (C1: 1 mg/kg BW; C2: 10 mg/kg BW; and C3: 100 mg/kg BW) eight weeks after ovariectomy for four weeks. Finally, femora and tibiae were collected. Biomechanical tests, micro-CT, ashing, histological and gene expression analyses were performed.

RESULTS

Biomechanical properties were unchanged in tibiae and reduced in femora. In tibiae, C1 treatment enhanced callus density and cortical width and decreased callus area. In the C3 group, callus formation was reduced during the first 3 weeks after osteotomy, correlating to a higher mRNA expression of Osteocalcin, Tartrate-resistant acid phosphatase and Rankl. In femora, baicalein treatments did not alter bone parameters.

CONCLUSIONS

Baicalein enhanced callus density and cortical width but impaired early callus formation in tibiae. In femora, it diminished the biomechanical properties and calcium-to-phosphate ratio. Thus, it is not advisable to apply baicalein to treat early bone fractures. To determine the exact effects on bone healing, further studies in which baicalein treatments are started at different stages of healing are needed.

Effect of zileuton on osteoporotic bone and its healing, expression of bone, and brain genes in rats

Estrogen deficiency and aging are associated with osteoporosis, impaired bone healing, and lower cognitive performance. Close functional and physical connections occur between bone and the central nervous system. An anti-inflammatory drug, zileuton (which is an inhibitor of arachidonate 5-lipoxygenase), is known to have a positive effect on bone tissue repair and brain ischemia. We studied the effect of zileuton on osteopenic bone and its healing and on the genes considered to be crucial for the cross talks between bone and brain. Three-month-old Sprague-Dawley rats were ovariectomized or left untreated. After 8 wk, bilateral metaphyseal tibia osteotomy with plate osteosynthesis was performed in all rats. Ovariectomized rats were fed with food containing zileuton (1, 10, or 100 mg/kg body wt) for 5 wk. In tibiae, bone volume, callus and cortical volume, and gene expression of osteocalcin and alkaline phosphatase were enhanced by zileuton (10 or 100 mg); biomechanical properties and bone density were not changed. In femur, zileuton enlarged cortical volume distal and trabecular volume proximal, decreasing their density. The expression level of brain Sema3a, known to regulate bone mass positively, was downregulated after ovariectomy. In contrast, bone Sema4d, a negative regulator of bone mass, was upregulated in the tibia callus after ovariectomy, whereas zileuton treatment (10 or 100 mg) resulted in reverse effects. Here, we describe for the first time the expression of Rbbp4 mRNA and its increase in tibia after ovariectomy. Zileuton caused downregulation of Rbbp4 in the hippocampus and had an effect on bone healing, changed the expression of genes involved in cross talk between bones and brain, and may be a potent drug for further examination in estrogen deficiency-related dysfunction(s). NEW & NOTEWORTHY Zileuton, a 5-lipoxygenase inhibitor, increased bone volume, callus and cortical volume in osteotomized tibia, and trabecular and cortical volume in femur. Although the expression of Sema3a (positively regulating bone mass) in brain was downregulated and Sema4d (negatively regulating bone mass) was upregulated in tibia callus after ovariectomy, zileuton could counteract these effects. Rbbp4 (involved in age-related memory loss) was increased in tibia callus after ovariectomy.

Effect of the lipoxygenase-inhibitors baicalein and zileuton on the vertebra in ovariectomized rats

Osteoporosis is one of the most common diseases worldwide. In osteoporosis, vertebral fractures represent a major burden. Lipoxygenase (LOX) inhibitors such as baicalein and zileuton may represent a promising therapeutic option owing to their antioxidative effects and suppression of various inflammatory processes in muscle and bone. The effect of these LOX inhibitors on the spine was studied in osteopenic rats. Female Sprague-Dawley rats were divided two times into five groups: four groups each were ovariectomized (OVX) and one control group was non-ovariectomized (NON-OVX). Eight weeks after ovariectomy, three concentrations of baicalein (1mg/kg body weight [BW], 10mg/kgBW, and 100mg/kgBW) were administered subcutaneously daily in three OVX groups for 4weeks. Similarly, zileuton was administered in three concentrations via food for 5weeks. In vivo computed tomography (pQCT) of the spine was performed before the treatments and at the end of the experiment. Lumbar vertebrae were subjected to a compression test, micro-CT, and ashing analyses. After baicalein treatment, cortical bone mineral density (BMD) was improved; trabecular connectivity and trabecular BMD were diminished at high dose. After zileuton treatment, the total BMD, anorganic weight, trabecular nodes, and trabecular area were improved. The in vivo stress-strain index was increased and alkaline phosphatase activity in serum was enhanced after both treatments. A dose-dependent effect was not clearly observed after both treatments. The treatments using baicalein for 4 and zileuton for 5weeks were not sufficient to change the biomechanical properties and bone volume fraction (BV/TV). Overall, baicalein improved the cortical bone parameters whereas zileuton had a favorable effect on the trabecular structure. Moreover, both treatments increased the bone formation rate. Longer trials, a combination of both LOX inhibitors, and their effect at the cellular and molecular levels should be investigated in further studies.

Protective effects of Huang-Lian-Jie-Du-Tang and its component group on collagen-induced arthritis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Huang-Lian-Jie-Du-Tang is a famous Traditional Chinese medicine consisting of Rhizoma coptidis (Coptis chinensis Franch, Ranunculaceae), Radix scutellariae (Scutellaria baicalensis Georgi, Labiatae), Cortex phellodendri (Phellodendron amurense Rupr. Rutaceae) and Fructus gardeniae (Gardenia jasminoide Ellis, Rubiaceae) in a weight ratio of 3:2:2:3.This formula was described by Wang Tao (in the Chinese Tang Dynasty) in his treatise "Wai Tai Mi Yao". It has been used to treat inflammation, hypertension, gastrointestinal disorders, and liver and cerebrovascular diseases in the clinical practice of Traditional Chinese medicine, especially in treating inflammation for nearly two thousand years. However, the essential compounds in it have not been identified, and the mechanisms remain to be addressed. To investigate the protective effects of HLJDT and its component group (HLJDT-CG) on collagen-induced arthritis in rats.

MATERIALS AND METHODS

CIA was established in male Wistar rats with subcutaneous injection of type II bovine collagen at the base of the tail of animals. CIA rats were treated daily with oral administration of HLJDT aqueous extracts (270 mg/kg) or HLJDT-CG (40 mg/kg) once per day from day 6 to day 28. Rats in normal and vehicle control groups were given an equal volume of vehicle (0.9% saline) and 0.025 mg/kg Dexamethasone was given to the Standard group at the same time. The protective effect of them were assessed by measuring arthritis index, swelling, the cytokines such as TNF-α, IFN-γ and IL-17 in serum, type II collagen antibodies, splenocyte proliferation and so on.

RESULTS

The results demonstrated that treatment of CIA rat with either HLJDT aqueous extracts or HLJDT-CG not only ameliorated the symptoms of arthritis, prevented joint damage but also reduced the serum levels of TNF-α, IFN-γ and IL-17 in CIA rats. Anti-CII antibodies showed the similar trend except that of IgG1. Furthermore, HLJDT aqueous extracts and HLJDT-CG administration also suppressed CII-induced proliferative response of splenocytes. More importantly, HLJDT-CG exhibited similar pharmacological activities as HLJDT aqueous extracts in all aforementioned experiments.

CONCLUSIONS

HLJDT aqueous extracts and HLJDT-CG could effectively ameliorate CII-induced arthritis and significantly suppress the immune response against CII with similar pharmacological efficacy. These findings suggest that HLJDT has therapeutic potential in RA treatment and HLJDT-CG can represent the effective-composite of HLJDT.

Estrogens and hyperglycemic modulation of mRNAs expressions involved in bone metabolism: an overshadowed association?

Human bone cell line (SaOS2) express different mRNAs involved in bone biology and physiology such as estrogen receptor α (ERα), estrogen receptor β (ERβ), vitamin D receptor (VDR), 1α, 25 hydroxy vitamin D(3) hydroxylase (1OHase) as well as 12 and 15 lipoxygenases (12LO and 15LO). These mRNAs are modulated by estrogenic compounds. Since the skeletal protective effects of estrogens are not discernible in diabetic women, we tested whether the expression of the parameters measured here and their modulations by estrogens, in SaOS2 cells grown in growth medium containing high glucose (HG; 9.0 g/L; 44 mM) compared to normal glucose (NG; 4.5 g/L; 22 mM). High Glucose (HG) significantly increased DNA synthesis and creatine kinase (CK) specific activity in SaOS2 cells. Stimulations of DNA but not of CK by E(2), by 4, 4', 4''-[4-propyl-(1H)-pyrazol-1, 3, 5- triyl] tris-phenol (PPT, ERα specific agonist), or by 2, 3-bis (4-hydroxyphenyl)-propionitrile (DPN, ERβ specific agonist), were abolished by HG. HG itself upregulated the expression of mRNA of 12LO and 15LO and upregulated to much less extent of ERβ and VDR, but had no effect on the expression of mRNA of ERα and 1OHase. The different hormonal treatments modulated the expressions of 12LO and 15LO mRNAs which was reduced in HG, whereas the induction of their products 12HETE and 15HETE was only slightly affected by HG. The exact mechanism of HG effects on bone cell responses is yet to be investigated and its relationship to human bone physiology is not yet clear.

Age-dependent responsiveness of human female bone cells to vitamin D analog and PTH

Vitamin D less-calcemic analog JKF 1624 F2-2 (JKF) and PTH 1-34 stimulate in human female cultured osteoblasts (Ob) DNA synthesis (DNA), creatine kinase specific activity (CK), 1α, 25 vitamin D hydroxylase mRNA (1OHase) expression and 1,25(OH)2D3 (1,25) production, estrogen receptors (ER) mRNA expression and intracellular and membranal estrogen binding. In the present study, cultured Ob from different ages were subjected to hormonal stimulations and analyzed for different parameters. We found: 1) ERα expression is higher and ERβ expression is lower in pre-meno - pausal Ob (prOb), with similar intracellular and membranal binding. 2) JKF and PTH up-regulated ERα and JKF downregulated ERβ in both Ob, while PTH stimulated it in post- (poOb) and inhibited it in prOb. 3) There is higher expression of 1OHase mRNA in prOb, but 1,25 production is similar. Both parameters were hormonally stimulated to higher extent in prOb. 4) Ob express 12 and 15 lipoxygenase (LO) mRNA and produce 12- and 15-hydroxyeicosatetraenoic acid (H). 12LO expression is higher and 15LO is lower in prOb, while 12H is higher in prOb and 15H is similar in both. JKF inhibited 12LO expression in prOb and stimulated in poOb, whereas PTH stimulated it to higher extent in prOb. JKF stimulated and PTH inhibited 15LO expression in both; 12 and 15H were stimulated by both hormones in both Ob. 5. PTH and JKF stimulated DNA and CK in both Ob. In conclusion Ob demonstrate some age-dependent response to calciotrophic hormones, but the mechanism and beneficial outcome for human is unclear.

Serum bone alkaline phosphatase in assessing illness severity of infected neonates in the neonatal intensive care unit

Background: Infections can influence bone metabolism of neonates, which may lead to changes in some bone metabolism biomarkers. The purpose of this study was to determine whether serum bone alkaline phosphatase (BALP), osteocalcin (OC) and beta carboxy-terminal peptide of type I collagen (CTX), as specific biomarkers of bone metabolism, can be used to assess the severity of neonatal infections.

Methods: Sixty-three neonates in the NICU were enrolled in this study. The neonates were divided into infected group (n=33) and non-infected group (n=30). The scores for neonatal acute physiology-perinatal extension II (SNAPPE-II) were calculated and interleukin-6 (IL-6), procalcitonin (PCT), BALP, OC and CTX were measured among the neonates with or without infections, and among the infected neonates before and after treatment.

Results: The serum BALP levels were lower in the infected group than that in the non-infected group (p<0.01). The serum BALP levels increased markedly in the infected neonates after treatment (p<0.01). The serum BALP levels were also inversely correlated with SNAPPE-II of infected neonates before and after treatment (r=-0.56, p<0.05; r=-0.37, p<0.05, respectively). In infected neonates, the differences between serum BALP levels before and after treatment were inversely correlated with those of IL-6 levels (p<0.05). There were no significant changes in the OC, CTX and PCT levels in the infected or non-infected group before and after treatment.

Conclusion: Our data suggest that serum BALP level might be used as a marker for assessing the severity of illness in infected neonates.

Sex specific response of cultured human bone cells to ERα and ERβ specific agonists by modulation of cell proliferation and creatine kinase specific activity

We have previously reported that human cultured bone cells (hObs) respond to estradiol-17β (E2) by stimulating DNA synthesis, creatine kinase BB specific activity (CK) and other parameters sex-specifically. We now investigate the sex specificity of the response of these hObs to estrogen receptor (ER) α and ERβ specific agonists. Real time PCR revealed that all cells express mRNA for both ERs. ERα mRNA but not ERβ mRNA was stimulated by all estrogenic compounds in both pre- and post-menopausal hObs with no effect in male hObs. Cells treated with E2, 2,3-bis (4-hydroxyphenyl)-propionitrile (DPN; ERβ specific agonist) and 4,4',4″-[4-propyl-(1H)-pyrazol-1,3,5-triyl] tris-phenol (PPT; ERα specific agonist) showed increased DNA synthesis and CK in all female but not male hObs. Raloxifene (Ral), a specific ERα antagonist, inhibited the stimulation of DNA synthesis and CK by E2 or PPT, but not by DPN. DPN and PPT like E2 modulated the expression of both 12 and 15 lipooxygenase (LO) mRNA in both female but not male hObs. 12 and 15 HETE production was modulated only by DPN and PPT in these cells. The LO inhibitor baicaleine inhibited only E2 and PPT but not DPN effects in both female hObs. In conclusion, we provide herein evidence for the separation of age- and sex-dependent mediation via both ERα and ERβ pathways in the effects of estrogens on hObs, with a yet unknown mechanism.

The effects of estrogen receptors α- and β-specific agonists and antagonists on cell proliferation and energy metabolism in human bone cell line

In cultured human osteoblasts estradiol-17β (E2) modulated DNA synthesis, the specific activity of creatine kinase BB (CK), 12 and 15 lipoxygenase (LO) mRNA expression and formation of 12- and 15-hydroxyeicosatetraenoic acid (HETE). We now investigate the response of human bone cell line (SaOS2) to phytoestrogens and estrogen receptors (ER)-specific agonists and antagonists. Treatment of SaSO2 with E2, 2,3-bis (4-hydroxyphenyl)-propionitrile (DPN; ERβ-specific agonist), 4,4',4″-[4-propyl-(1H)-pyrazol-1,3,5-triyl] tris-phenol (PPT; ERα-specific agonist), biochainin A (BA), daidzein (D), genistein (G) and raloxifene (Ral) showed increased DNA synthesis and CK. Ral inhibited completely all stimulations except DPN and to some extent D. The ERα-specific antagonist methyl-piperidino-pyrazole (MPP) and the ERβ-specific antagonist 4-[2-phenyl-5,7-bis (tri-fluoro-methyl) pyrazolo [1,5-a]pyrimidin-3-yl] phenol (PTHPP) inhibited DNA synthesis, CK and reactive oxygen species (ROS) formation induced by estrogens according to their receptors affinity. The LO inhibitor baicaleine inhibited only E2, DPN and G's effects. E2 and Ral unlike all other compounds had no effect on ERα mRNA expression, while ERβ mRNA expression was stimulated by all compounds. All compounds modulated the expression of 12LO and 15LO mRNA, except E2, PPT and Ral for 12LO, and 12- and 15-HETE productions and stimulated ROS formation which was inhibited by NADPH oxidase inhibitors diphenyleneiodonium chloride (DPI) and N-acetyl cysteine and the estrogen inhibitor ICI. DPI did not affect hormonal-induced DNA and CK. In conclusion, we provide evidence for the separation of mediation via ERα and ERβ pathways in the effects of estrogenic compounds on osteoblasts, but the role of LO/HETE/ROS is unclear.

Vitamin D metabolites and analogs induce lipoxygenase mRNA expression and activity as well as reactive oxygen species (ROS) production in human bone cell line

Vitamin D metabolites and its less-calcemic analogs (vitamin D compounds) are beneficial for bone and modulate cell growth and energy metabolism. We now analyze whether 25(OH)D(3) (25D), 1,25(OH)(2)D(3) (1,25D), 24,25(OH)(2)D(3) (24,25D), JKF1624F(2)-2 (JKF) or QW1624F(2)-2 (QW) regulate lipooxygenase (LO) mRNA expression and its products; hydroxyl-eicosatetraenoic acid (12 and 15HETE) formation, as well as reactive oxygen species (ROS) production in human bone cell line (SaOS2) and their interplay with modulation of cell proliferation and energy metabolism. All compounds except 25D increased 12LO mRNA expression and modulated 12 and 15HETE production whereas ROS production was increased by all compounds, and inhibited by NADPH oxidase inhibitors diphenyleneiodonium (DPI) and N-acetylcysteine (NAc). Baicaleine (baic) the inhibitor of 12 and 15LO activity blocked only slightly the stimulation of DNA synthesis by all compounds, whereas DPI inhibited almost completely the stimulation of DNA and CK by all compounds. Treatments of cells with 12 or 15HETE increased DNA synthesis and CK that were only slightly inhibited by DPI. These results indicate that vitamin D compounds increased oxidative stress in osteoblasts in part via induction of LO expression and activity. The increased ROS production mediates partially elevated cell proliferation and energy metabolism, whereas the LO mediation is not essential. This new feature of vitamin D compounds is mediated by intracellular and/or membranal binding sites and its potential hazard could lead to damage due to increased lipid oxidation, although the transient mediation of ROS in cell proliferation is beneficial to bone growth in a yet unknown mechanism.

Phospholipase C signaling via the parathyroid hormone (PTH)/PTH-related peptide receptor is essential for normal bone responses to PTH

We have previously shown that differentiation of hypertrophic chondrocytes is delayed in mice expressing a mutated PTH/PTHrP receptor (PTHR) (called DSEL here) that stimulates adenylyl cyclase normally but fails to activate phospholipase C (PLC). To better understand the role of PLC signaling via the PTHR in skeletal and mineral homeostasis, we examined these mice fed a normal or calcium-deficient diet. On a standard diet, DSEL mice displayed a modest decrease in bone mass. Remarkably, when fed a low-calcium diet or infused with PTH, DSEL mice exhibited strikingly curtailed peritrabecular stromal cell responses and attenuated new bone formation when compared with Wt mice. Attenuated in vitro colony formation was also observed in bone marrow cells derived from DSEL mice fed a low-calcium diet. Furthermore, PTH stimulated proliferation and increased mRNAs encoding cyclin D1 in primary osteoblasts derived from Wt but not from DSEL mice. Our data indicate that PLC signaling through the PTHR is required for skeletal homeostasis.

Vitamin D analogs induce lipoxygenase mRNA expression and activity as well as reactive oxygen species (ROS) production in human bone cells

Vitamin D metabolites or its less-calcemic analogs (JKF or QW) are beneficial for bone biology. We analyzed whether or not 25(OH)D3 (25), 1,25(OH)2D3 (1,25), JKF or QW regulate lipooxygenase (LO) enzymes expression and their products hydroxyeicosatetraenoic acid (12 and 15 HETE) formation as well as reactive oxygen species (ROS) production in human bone cell lines (SaOS2 and hFOB) and primary cultured human bone cells (Obs) from males or females. All compounds except 25 increased LOs mRNA expression and HETE production in female or male Obs. ROS formation was induced by JKF and QW in both cell lines, and was inhibited by different inhibitors. Baicalein (baic) an inhibitor of 12 and 15 LO activity, inhibited partially ROS formation by JKF or QW in SaSO2 and hFOB. JKF-stimulated DNA synthesis in female Obs was inhibited by baic but unchanged by addition of HETE or HETE with baic. These results indicate that vitamin D increased oxidative stress in bone cells is in part via induction of LO expression and activity. This new feature of vitamin D is probably mediated by intracellular and/or membranal receptors and its potential hazard could lead to potential damage due to increased lipid oxidation.

Huang-Lian-Jie-Du-Tang exerts anti-inflammatory effects in rats through inhibition of nitric oxide production and eicosanoid biosynthesis via the lipoxygenase pathway

Objectives

Huang-Lian-Jie-Du-Tang (HLJDT) is a traditional Chinese medicine with a long history of anti-inflammatory use, but its pharmacological effects have not been thoroughly investigated. This study aimed to evaluate the anti-inflammatory activity of HLJDT in vivo and in vitro.

Methods

The carrageenan rat air pouch model was used to investigate the anti-inflammatory action of HLJDT after oral administration. Moreover, we exploited a modified method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) technique to assay the effects of HLJDT on arachidonic acid metabolites.

Key findings

Our data demonstrate that oral administration of HLJDT significantly inhibited the inflammatory responses in carrageenan-injected rat air pouches, and also significantly reduced the production of nitric oxide (NO) and leukotriene B4 (LTB4) in vivo, without any influence on biosynthesis of cyclooxygenase (COX)-derived eicosanoids. Similar behaviour of HLJDT was also observed by using calcium ionophore A23187-stimulated peritoneal macrophages, where HLJDT markedly inhibited eicosanoids derived from different lipoxygenases. The NO production and the mRNA expression of inducible nitric oxide synthase (iNOS) and chemotactic factors (CCL3, CCL4, CCL5 and CXCL2) were also inhibited by HLJDT in RAW 264.7 macrophages stimulated by lipopolysaccharide.

Conclusions

Our data revealed, for the first time, that HLJDT could inhibit biosynthesis of eicosanoids derived from different lipoxygenases. Also, HLJDT may exert its anti-inflammatory effects by its suppression on eicosanoid generation, NO production and gene transcription of chemotactic factors, which supports its effectiveness in the treatment of inflammatory diseases.