Long-term comparative study of Substance-P with methylprednisolone on the development of osteoporosis

Emerging roles of nerve-bone axis in modulating skeletal system

Over the past decades, emerging evidence in the literature has demonstrated that the innervation of bone is a crucial modulator for skeletal physiology and pathophysiology. The nerve-bone axis sparked extensive preclinical and clinical investigations aimed at elucidating the contribution of nerve-bone crosstalks to skeleton metabolism, homeostasis, and injury repair through the perspective of skeletal neurobiology. To date, peripheral nerves have been widely reported to mediate bone growth and development and fracture healing via the secretion of neurotransmitters, neuropeptides, axon guidance factors, and neurotrophins. Relevant studies have further identified several critical neural pathways that stimulate profound alterations in bone cell biology, revealing a complex interplay between the skeleton and nerve systems. In addition, inspired by nerve-bone crosstalk, novel drug delivery systems and bioactive materials have been developed to emulate and facilitate the process of natural bone repair through neuromodulation, eventually boosting osteogenesis for ideal skeletal tissue regeneration. Overall, this work aims to review the novel research findings that contribute to deepening the current understanding of the nerve-bone axis, bringing forth some schemas that can be translated into the clinical scenario to highlight the critical roles of neuromodulation in the skeletal system.

Transcriptomic analysis of World Trade Center particulate Matter-induced pulmonary inflammation and drug treatments

Over 400,000 people are estimated to have been exposed to World Trade Center particulate matter (WTC_PM) since the attack on the Twin Towers in Lower Manhattan on September 11, 2001. Epidemiological studies have found that exposure to dust may cause respiratory ailments and cardiovascular diseases. However, limited studies have performed a systematic analysis of transcriptomic data to elucidate the biological responses to WTC_PM exposure and the therapeutic options. Here, we developed an in vivo mouse exposure model of WTC_PM and administered two drugs (i.e., rosoxacin and dexamethasone) to generate transcriptomic data from lung samples. WTC_PM exposure increased the inflammation index, and this index was significantly reduced by both drugs. We analyzed the transcriptomics derived omics data using a hierarchical systems biology model (HiSBiM) with four levels, including system, subsystem, pathway, and gene analyses. Based on the selected differentially expressed genes (DEGs) from each group, WTC_PM and the two drugs commonly affected the inflammatory responses, consistent with the inflammation index. Among these DEGs, the expression of 31 genes was affected by WTC_PM exposure and consistently reversed by the two drugs, and these genes included Psme2, Cldn18, and Prkcd, which are involved in immune- and endocrine-related subsystems and pathways such as thyroid hormone synthesis, antigen processing and presentation, and leukocyte transendothelial migration. Furthermore, the two drugs reduced the inflammatory effects of WTC_PM through distinct pathways, e.g., vascular-associated signaling by rosoxacin, whereas mTOR-dependent inflammatory signaling was found to be regulated by dexamethasone. To the best of our knowledge, this study constitutes the first investigation of transcriptomics data of WTC_PM and an exploration of potential therapies. We believe that these findings provide strategies for the development of promising optional interventions and therapies for airborne particle exposure.

Targeted delivery of dexamethasone in acute pneumonia

Pneumonia has contributed to significant mortality owing to the irreversible injury to the lungs and severe inflammation of the tissue. Dexamethasone (DEX) is regarded as an effective drug to relieve the level of pneumonia, while the adverse effect of which is non-negligible. Here, we developed a targeted delivery strategy based on platelet-derived extracellular vesicles (PEVs), which are naturally occurring nanoparticles released by platelets, for DEX delivery in acute pneumonia, aiming to reduce the side effects and improve the therapeutic efficacy. Our strategy may shed light on the problems in DEX-based acute pneumonia therapy clinically.

Substance P enhances the therapeutic effect of MSCs by modulating their angiogenic potential

Bone marrow mesenchymal stem cell (MSC) therapy acts through multiple differentiations in damaged tissue or via secretion of paracrine factors, as demonstrated in various inflammatory and ischaemic diseases. However, long‐term ex vivo culture to obtain a sufficient number of cells in MSC transplantation leads to cellular senescence, deficiency of the paracrine potential, and loss of survival rate post‐transplantation. In this study, we evaluated whether supplementation of MSCs with substance P (SP) can improve their therapeutic potential. SP treatment elevated the secretion of paracrine/angiogenic factors, including VEGF, SDF‐1a and PDGF‐BB, from late passage MSCs in vitro. MSCs supplemented with SP accelerated epidermal/dermal regeneration and neovascularization and suppressed inflammation in vivo, compared to MSCs transplanted alone. Importantly, supplementation with SP enabled the incorporation of transplanted human MSCs into the host vasculature as pericytes via PDGF signalling, leading to the direct engagement of transplanted cells in compact vasculature formation. Our results showed that SP is capable of restoring the cellular potential of senescent stem cells, possibly by modulating the generation of paracrine factors from MSCs, which might accelerate MSC‐mediated tissue repair. Thus, SP is anticipated to be a potential beneficial agent in MSC therapy for inflammatory or ischaemic diseases and cutaneous wounds.

Effects of water extract from epimedium on neuropeptide signaling in an ovariectomized osteoporosis rat model

ETHNOPHARMACOLOGICAL RELEVANCE

For the past millennium, water extract from Epimedium (dried leaves of Epimedium brevicornu Maxim.) has been widely used for bone disease therapy in traditional Chinese medicine and has been reported to exhibit salutary effects on osteoporosis in clinical trials. The therapeutic effect of Epimedium is associated with the function of the brain in traditional Chinese medicine theory.

STUDY AIM

To determine the potential relationship between treating osteoporosis with Epimedium and neuropeptide regulation.

MATERIALS AND METHODS

Water extract from Epimedium was qualitatively and quantitatively analyzed with HPLC-TOF-MS. Ovariectomized rats were used as an osteoporosis model and were treated orally with water extract from Epimedium 16 weeks after surgery to mimic clinical therapy. After treatment, gene expression and protein levels of four neuropeptides, as well as their main receptors or receptor precursors including; neuropeptide Y (NPY) and its receptors NPY 1 (NPYR1) and 2; calcitonin gene-related peptide and its receptor precursor calcitonin receptor-like receptor (CRLR); vasoactive intestinal peptide (VIP) and its receptor VIP 1 (VIP1R) and 2; and substance P (SP) and its receptor neurokinin 1 receptor (NK1R) were detected in samples taken from bone, brain and spinal cord.

RESULTS

Treatment with water extract from Epimedium prevented bone mineral loss and reduced femoral bone strength decline associated with osteoporosis. Detection of neuropeptides showed that treatment also affected neuropeptide in the brain/spinal cord/bone axis; specifically, treatment increased brain NPY, bone NPY1R, bone CRLR, bone and spinal cord VIP and VIP2R, bone SP, and brain and spinal cord NK1R.

CONCLUSION

The effects of osteoporosis can largely be reduced by treatment with Epimedium most likely through a mechanism associated with several neuropeptides involved in regulation of the brain/spinal cord/bone axis. These novel results contribute to existing literature regarding the possible mechanisms of habitual use of Epimedium in the treatment of osteoporosis.

Metabolomics Based Profiling of Dexamethasone Side Effects in Rats

Dexamethasone (Dex) is a synthetic glucocorticoid that has anti-inflammatory and immunosuppressant effects and is used in several conditions such as asthma and severe allergy. Patients receiving Dex, either at a high dose or for a long time, might develop several side effects such as hyperglycemia, weight change, or osteoporosis due to its in vivo non-selectivity. Herein, we used liquid chromatography-tandem mass spectrometry-based comprehensive targeted metabolomic profiling as well as radiographic imaging techniques to study the side effects of Dex treatment in rats. The Dex-treated rats suffered from a ∼20% reduction in weight gain, hyperglycemia (145 mg/dL), changes in serum lipids, and reduction in total serum alkaline phosphatase (ALP) (∼600 IU/L). Also, compared to controls, Dex-treated rats showed a distinctive metabolomics profile. In particular, serum amino acids metabolism showed six-fold reduction in phenylalanine, lysine, and arginine levels and upregulation of tyrosine and hydroxyproline reflecting perturbations in gluconeogenesis and protein catabolism which together lead to weight loss and abnormal bone metabolism. Sorbitol level was markedly elevated secondary to hyperglycemia and reflecting activation of the polyol metabolism pathway causing a decrease in the availability of reducing molecules (glutathione, NADPH, NAD+). Overexpression of succinylacetone (4,6-dioxoheptanoic acid) suggests a novel inhibitory effect of Dex on hepatic fumarylacetoacetate hydrolase. The acylcarnitines, mainly the very long chain species (C12, C14:1, C18:1) were significantly increased after Dex treatment which reflects degradation of the adipose tissue. In conclusion, long-term Dex therapy in rats is associated with a distinctive metabolic profile which correlates with its side effects. Therefore, metabolomics based profiling may predict Dex treatment-related side effects and may offer possible novel therapeutic interventions.

Effect of glucocorticoid withdrawal on glucocorticoid inducing bone impairment

Glucocorticoid (GC) withdrawal after a short-term use was common in clinical practice like immediate post-transplant period. However, previous studies without setting age-control group failed to determine whether the BMD recovery was sufficient and whether it is necessary to accept anti-osteoporosis therapy after GC withdrawal. The aim of this study was to investigate the effect of GC withdrawal on bone impairment in glucocorticoid-induced osteoporosis (GIOP) rats. Twenty-four female Sprague-Dawley rats (3 months' old) were randomly divided into two treatment groups: an untreated age-control group (Con, n = 12); another group receiving a dexamethasone injection (DEXA, n = 12). Animals in the Con group were euthanized at 3rd month (M3) and 6th month (M6), respectively. Six rats in the DEXA group were euthanized at 3rd month (M3), whereas GC intervention was withdrew in the remaining animals of DEXA group, which were euthanized at the end of 6th month (M6). Bone mass, bone microarchitecture, biomechanical properties of vertebrae, morphology, serum levels of PINP and β-CTX were evaluated. Compared with the Con(M3) group, the Con(M6) group showed significantly better bone quantity, morphology and quality. Compared with the Con(M3) group, the DEXA (M3) group showed significantly lower BMC, BMD, BS/TV, BV/TV, Tb.N, Tb.Th, vBMD, bone strength, compressive displacement, energy absorption capacity, PINP levels, β-CTX levels, and damaged trabecular morphology. And the same change trend was observed in the comparison between the Con(M6) group and DEXA (M6) group. Compared with the DEXA (M3) group, the DEXA (M6) group showed significantly higher BMC, BMD and AREA, but no significant difference in BS/TV, BV/TV, SMI, Tb.N, Tb.Th, Tb.Sp, vBMD, bone strength, bone stiffness, compressive displacement, energy absorption capacity, PINP levels, β-CTX levels, and improvement in trabecular morphology was observed. These results indicate that the reverse effect of GC withdrawal for 3 months on bone impairment in GIOP rats was insufficient, which implied that related anti-osteoporosis treatment might be still necessitated after GC withdrawal in clinical setting.

Effect of substance P on recovery from laser-induced retinal degeneration

Retinal degeneration is caused by neovascularization and persistent inflammation in the retinal pigment epithelium (RPE) and choroid, and causes serious eye disease including age-related macular degeneration (AMD). Thus, inhibiting inflammation and neovascularization may be a primary approach to protect the retina from degeneration. The purpose of this study was to determine whether substance P (SP), which can suppress inflammation and mobilize stem cells, can protect the RPE from degeneration. The effect of SP was evaluated by analyzing systemic inflammation, cell survival, and neovascularization within the argon laser-injured retina of mice. At 1 week postinjury, the SP-treated group had lower tumor necrosis factor-alpha and higher interleukin-10 serum concentrations, and a more intact retinal structure compared to the vehicle-treated group. In mice administered SP repeatedly for 4 weeks, the retinal structure appeared normal and showed sparse neovascularization, whereas the vehicle-treated group showed severe retinal destruction and dense neovascularization. Moreover, the efficacy of SP was identical to that of mesenchymal stem cells that were transplanted into the vitreous after retinal injury. This study highlights the potential for the endogenous neuropeptide SP as a treatment for retinal damage to prevent conditions such as AMD.

Variance of spinal osteoporosis induced by dexamethasone and methylprednisolone and its associated mechanism

BACKGROUND

Glucocorticoid (GC) administration is the most common cause of secondary osteoporosis. Previous studies investigated GCs dose and frequency correlated positively with the side effects of glucocorticoid on bone health, however the impaired effect of various types of GCs on bone has not yet been reported.

PURPOSE

The aim is to compare the effect of long-acting (dexamethasone) and relatively short-acting glucocorticoid (methylprednisolone) on rat lumbar spine and try to explore the associated mechanism.

METHOD

Sprague Dawley rats (N=48) were randomly divided into four groups: baseline group (BL), control group (CON), methylprednisolone group (MP) and dexamethasone group (DEXA). BL rats were euthanized to remain as baseline (M0) at the beginning of experiment. CON group were injected daily with vehicle, while the other groups were given a daily subcutaneous injection of 1mg/kg methylprednisolone and were given a subcutaneous injection of 0.6mg/kg dexamethasone per 3days, respectively. CON, MP and DEXA groups were monitored at 4th week (M1), 8th week (M2) and 12th week (M3) after intervention. Dual-energy X-ray, micro-computed tomography, compressive test, enzyme-linked immunosorbent assay have been used for bone mineral density, microarchitecture, biomechanical property of vertebrae and levels of estrogen, PINP and β-CTX, respectively. mRNA expression analysis of Biglycan, Col1a1, MMP9, Cathepsin K, Runx2, OPG, LRP5, Sclerostin were performed.

RESULT

We found that the bone mineral density (BMD) was significantly lower in DEXA rats at M3 compared with MP rats. The relative surface and trabecular number were significantly lower in DEXA group than that in MP group at M2, while trabecular separation was significantly higher in DEXA group than that in MP group at the same point. The compressive strength was significantly lower in L4 of DEXA than that in MP rats at M2 and M3. The levels of both PINP and estradiol in DEXA group were lower than MP group at M3, even though without statistical significance. The expression of bone formation marker Runx2 was significantly down-regulated at M3 in DEXA group compared with MP, CON and BL groups, while the expression of Col1a1 was significantly up-regulated and biglycan, LRP-5, OPG were significantly down-regulated in GCs intervention groups compared with CON and BL groups. There were no statistical differences in MMP9, Cathepsin K, Sclerostin among CON, MP and DEXA groups.

CONCLUSION

These results indicate that dexamethasone, the long-acting glucocorticoid, generates more serious osteoporosis of rat lumbar spine than methylprednisolone, which is relatively short-acting glucocorticoid. The discrepancy between the two GCs inducing osteoporosis may be mainly caused by a decrease in bone formation. RUNX2 and Col1a1 may be the two of critical genes inducing the discrepant impairment.