Substance P ameliorates collagen II-induced arthritis in mice via suppression of the inflammatory response

Osteoporotic Bone Regeneration via Plenished Biomimetic PLGA Scaffold with Sequential Release System

Achieving satisfactory bone tissue regeneration in osteoporotic patients with ordinary biomaterials is challenging because of the decreased bone mineral density and aberrant bone microenvironment. In addressing this issue, a biomimetic scaffold (PMEH/SP), incorporating 4-hexylresorcinol (4HR), and substance P (SP) into the poly(lactic-go-glycolic acid) (PLGA) scaffold with magnesium hydroxide (M) and extracellular matrix (E) is introduced, enabling the consecutive release of bioactive agents. 4HR and SP induced the phosphorylation of p38 MAPK and ERK in human umbilical vein endothelial cells (HUVECs), thereby upregulating VEGF expression level. The migration and tube-forming ability of endothelial cells can be promoted by the scaffold, which accelerates the formation and maturation of the bone. Moreover, 4HR played a crucial role in the inhibition of osteoclastogenesis by interrupting the IκB/NF-κB signaling pathway and exhibiting SP, thereby enhancing the migration and angiogenesis of HUVECs. Based on such a synergistic effect, osteoporosis can be suppressed, and bone regeneration can be achieved by inhibiting the RANKL pathway in vitro and in vivo, which is a commonly known mechanism of bone physiology. Therefore, the study presents a promising approach for developing a multifunctional regenerative material for sophisticated osteoporotic bone regeneration.

Stroke risk in rheumatoid arthritis patients: exploring connections and implications for patient care

Rheumatoid arthritis (RA) can independently increase the risk of stroke, affecting both young and adult RA patients. Recent attention has been drawn to the association between stroke and RA, supported by mounting evidence. Given that stroke is a significant and an urgent public health concern, this review aims to highlight the relationship between stroke and RA, covering mechanisms, underlying risk factors, early detection tools, and treatment implications. By uncovering the connection that links RA to stroke, we can pave the way for targeted healthcare practices and the development of preventive strategies for individuals with RA. Therefore, further research is imperative to deepen our understanding of this association and, ideally, guide treatment decisions for individuals at risk of both RA and stroke.

Nociceptor-Macrophage Interactions in Apical Periodontitis: How Biomolecules Link Inflammation with Pain

Periradicular tissues have a rich supply of peripheral afferent neurons, also known as nociceptive neurons, originating from the trigeminal nerve. While their primary function is to relay pain signals to the brain, these are known to be involved in modulating innate and adaptive immunity by initiating neurogenic inflammation (NI). Studies have investigated neuroanatomy and measured the levels of biomolecules such as cytokines and neuropeptides in human saliva, gingival crevicular fluid, or blood/serum samples in apical periodontitis (AP) to validate the possible role of trigeminal nociceptors in inflammation and tissue regeneration. However, the contributions of nociceptors and the mechanisms involved in the neuro-immune interactions in AP are not fully understood. This narrative review addresses the complex biomolecular interactions of trigeminal nociceptors with macrophages, the effector cells of the innate immune system, in the clinical manifestations of AP.

The role of substance P on maintaining ligament homeostasis by inhibiting endochondral ossification during osteoarthritis progression

PURPOSE

Osteoarthritis (OA) is characterized by the degeneration of various tissues, including ligaments. However, pathological changes such as chondrogenesis and ossification in ligaments during OA are still unclear. Substance P (SP), a neuropeptide, has various functions including bone metabolism. This study aimed to analyze the expression and function of SP in OA ligaments, and the therapeutic potential of SP agonists in OA mice.

MATERIALS AND METHODS

Expressions of SP, SOX9, and MMP13 were histologically analyzed in the posterior cruciate ligament (PCL) in humans with OA and Senescence-accelerated mouse-prone 8 (SAMP8) mice as a spontaneous OA model. The effect of SP agonists on chondrogenesis was evaluated using human ligament cells. Finally, SP agonists were administered intraperitoneally to destabilized medial meniscus (DMM) mice, and the PCL was histologically evaluated.

RESULTS

In PCL of humans and mice, the expression of SP, SOX9, and MMP13 was upregulated as OA progressed, but their expression was downregulated in severe degeneration. SP and SOX9 were co-expressed in chondrocyte-like cells. In ligament cells, SP agonists downregulated SOX9, RUNX2, and COL10A1. On evaluating chondrogenesis in ligament cells, pellet diameter was reduced in those treated with the SP agonists compared to those untreated. Administration of SP agonists ameliorated PCL degeneration in DMM mice. The Osteoarthritis Research Society and ligament scores in mice with SP agonists were significantly lower than those without SP agonists.

CONCLUSIONS

SP plays an important role in maintaining ligament homeostasis by inhibiting endochondral ossification during OA progression. Targeting SP has therapeutic potential for preventing ligament degeneration.

Regulation of Carcinogenesis by Sensory Neurons and Neuromediators

Simple Summary

Sensory nerve fibers extensively innervate the entire body. They are the first to sense danger signals, including the ones coming from newly formed cancer cells. Various studies have demonstrated that the inactivation of sensory nerve fibers as well as the vagus nerve enhances tumor growth and spread in models including breast, pancreatic, and gastric cancer. On the other hand, there are also contradictory findings that show the opposite, namely that the inactivation of nerve fibers inhibits tumor growth. These discrepancies are likely caused by the stage and the level of aggressiveness of the tumor model used. Hence, further studies are required to determine the factors involved in neuro-immunological mechanisms of tumor growth and spread.

Abstract

Interactions between the immune system and the nervous system are crucial in maintaining homeostasis, and disturbances of these neuro-immune interactions may participate in carcinogenesis and metastasis. Nerve endings have been identified within solid tumors in humans and experimental animals. Although the involvement of the efferent sympathetic and parasympathetic innervation in carcinogenesis has been extensively investigated, the role of the afferent sensory neurons and the neuropeptides in tumor development, growth, and progression is recently appreciated. Similarly, current findings point to the significant role of Schwann cells as part of neuro-immune interactions. Hence, in this review, we mainly focus on local and systemic effects of sensory nerve activity as well as Schwann cells in carcinogenesis and metastasis. Specific denervation of vagal sensory nerve fibers, or vagotomy, in animal models, has been reported to markedly increase lung metastases of breast carcinoma as well as pancreatic and gastric tumor growth, with the formation of liver metastases demonstrating the protective role of vagal sensory fibers against cancer. Clinical studies have revealed that patients with gastric ulcers who have undergone a vagotomy have a greater risk of stomach, colorectal, biliary tract, and lung cancers. Protective effects of vagal activity have also been documented by epidemiological studies demonstrating that high vagal activity predicts longer survival rates in patients with colon, non-small cell lung, prostate, and breast cancers. However, several studies have reported that inhibition of sensory neuronal activity reduces the development of solid tumors, including prostate, gastric, pancreatic, head and neck, cervical, ovarian, and skin cancers. These contradictory findings are likely to be due to the post-nerve injury-induced activation of systemic sensory fibers, the level of aggressiveness of the tumor model used, and the local heterogeneity of sensory fibers. As the aggressiveness of the tumor model and the level of the inflammatory response increase, the protective role of sensory nerve fibers is apparent and might be mostly due to systemic alterations in the neuro-immune response. Hence, more insights into inductive and permissive mechanisms, such as systemic, cellular neuro-immunological mechanisms of carcinogenesis and metastasis formation, are needed to understand the role of sensory neurons in tumor growth and spread.

Substance P, A Promising Therapeutic Target in Musculoskeletal Disorders

A large number of studies have focused on the role of substance P (SP) and the neurokinin-1 receptor (NK1R) in the pathogenesis of a variety of medical conditions. This review provides an overview of the role of the SP-NK1R pathway in the pathogenesis of musculoskeletal disorders and the evidence for its role as a therapeutic target for these disorders, which are major public health problems in most countries. To summarize, the brief involvement of SP may affect tendon healing in an acute injury setting. SP combined with an adequate conjugate can be a regenerative therapeutic option in osteoarthritis. The NK1R antagonist is a promising agent for tendinopathy, rheumatoid arthritis, and osteoarthritis. Research on the SP-NK1R pathway will be helpful for developing novel drugs for osteoporosis.

Therapeutic effect of targeting Substance P on the progression of osteoarthritis

OBJECTIVES

Substance P (SP) modulates NK1 and has various functions such as regulation of pain response, bone metabolism, and angiogenesis, which are recognized as important factors in osteoarthritis (OA). We aimed to evaluate the therapeutic effect of targeting SP on OA progression.

METHODS

SP expression patterns were analysed histologically in articular cartilage and subchondral bone of human knees from OA patients and autopsy donors as non-OA samples and in mouse articular cartilage. Moreover, to examine the effect of SP on the progression of OA, we administered drugs to mice following the surgical destabilization of the medial meniscus: Phosphate-buffered saline (PBS), septide (NK1 receptor agonist), or aprepitant (NK1 receptor antagonist). Histological analysis and bone morphologic analysis using micro-computed tomography were performed.

RESULTS

In human analysis, the expression of SP in mild OA samples was significantly higher than that in severe OA, and that in healthy cartilage was significantly higher than that in OA. In mouse analysis, Osteoarthritis Research Society International scores in the septide group were significantly lower than those in the control group. Computed tomography analysis showed that the subchondral bone's epiphysis in the control group had sclerotic change, not observed in the septide group.

CONCLUSIONS

The administration of septide ameliorates OA progression through preventing subchondral bone sclerosis.

Macrophage as a Peripheral Pain Regulator

A neuroimmune crosstalk is involved in somatic and visceral pathological pain including inflammatory and neuropathic components. Apart from microglia essential for spinal and supraspinal pain processing, the interaction of bone marrow-derived infiltrating macrophages and/or tissue-resident macrophages with the primary afferent neurons regulates pain signals in the peripheral tissue. Recent studies have uncovered previously unknown characteristics of tissue-resident macrophages, such as their origins and association with regulation of pain signals. Peripheral nerve macrophages and intestinal resident macrophages, in addition to adult monocyte-derived infiltrating macrophages, secrete a variety of mediators, such as tumor necrosis factor-α, interleukin (IL)-1β, IL-6, high mobility group box 1 and bone morphogenic protein 2 (BMP2), that regulate the excitability of the primary afferents. Neuron-derived mediators including neuropeptides, ATP and macrophage-colony stimulating factor regulate the activity or polarization of diverse macrophages. Thus, macrophages have multitasks in homeostatic conditions and participate in somatic and visceral pathological pain by interacting with neurons.

Substance-P prevents the cholestatic liver injury by regulating inflammatory responses

Substance-P (SP) is a neuropeptide that modulates immune responses and accelerates tissue repair in critical inflammatory disease. Liver fibrosis and cirrhosis are the ultimate outcomes of almost all chronic liver diseases caused by viral infection, steatohepatitis, autoimmune, and cholestatic injury. Despite the development of new drugs, liver transplantation is still the only fundamental treatment; thus, new therapeutic approaches to mitigate liver fibrosis and chronic inflammation are constantly being needed. The aim of this study was to examine the effect of SP on liver damage due to cholestatic stress. To induce cholestatic injury, common bile duct ligation (CBDL) was attempted, followed by systemic application of SP. SP treatment increased IL-10 and decreased TNF-α in serum with increasing levels of circulating regulatory T cells (Tregs) from the early stage of CBDL. Moreover, SP decreased CBDL-induced TGF-β1 expression in the circulation. This could create anti-inflammatory/anti-fibrotic environment under CBDL, which might ameliorate the progression of liver fibrosis in CBDL. Histological and molecular analysis revealed that SP treatment reduced ductular reaction, hepatic damage, and apoptotic hepatocytes, accompanied by diminishing type I collagen and upregulating MMP-9. These studies found that SP is a promising therapeutic candidate for immune-related liver disease as well as cholestatic liver disease, by providing hepatic protective effects via immune suppression.

Immune Actions on the Peripheral Nervous System in Pain

Pain can be induced by tissue injuries, diseases and infections. The interactions between the peripheral nervous system (PNS) and immune system are primary actions in pain sensitizations. In response to stimuli, nociceptors release various mediators from their terminals that potently activate and recruit immune cells, whereas infiltrated immune cells further promote sensitization of nociceptors and the transition from acute to chronic pain by producing cytokines, chemokines, lipid mediators and growth factors. Immune cells not only play roles in pain production but also contribute to PNS repair and pain resolution by secreting anti-inflammatory or analgesic effectors. Here, we discuss the distinct roles of four major types of immune cells (monocyte/macrophage, neutrophil, mast cell, and T cell) acting on the PNS during pain process. Integration of this current knowledge will enhance our understanding of cellular changes and molecular mechanisms underlying pain pathogenies, providing insights for developing new therapeutic strategies.

Neuromodulation of bone: Role of different peptides and their interactions (Review)

Our understanding of the skeletal system has been expanded upon the recognition of several neural pathways that serve important roles in bone metabolism and skeletal homeostasis, as bone tissue is richly innervated. Considerable evidence provided by in vitro, animal and human studies have further elucidated the importance of a host of hormones and local factors, including neurotransmitters, in modulating bone metabolism and osteo-chondrogenic differentiation, both peripherally and centrally. Various cells of the musculoskeletal system not only express receptors for these neurotransmitters, but also influence their endogenous levels in the skeleton. As with a number of physiological systems in nature, a neuronal pathway regulating bone turnover will be neutralized by another pathway exerting an opposite effect. These neuropeptides are also critically involved in articular cartilage homeostasis and pathogenesis of degenerative joint disorders, such as osteoarthritis. In the present Review, data on the role of several neuronal populations in nerve-dependent skeletal metabolism is examined, and the molecular events involved are explored, which may reveal broader relationships between two apparently unrelated organs.

Substance P blocks ovariectomy-induced bone loss by modulating inflammation and potentiating stem cell function

Osteoporosis is an age-related disease caused by imbalanced bone remodeling resulting from excessive bone resorption. Osteoporosis is tightly linked with induction of chronic inflammation, which activates osteoclasts and impairs osteoprogenitor in bone marrow. T helper 17 (Th17) cells have been recently recognized as one of major inducers in the pathophysiology of bone loss by secreting IL-17. Thus, modulation of Th17 development is anticipated to affect the progression of osteoporosis.

Substance P (SP) is reported to provide anti-inflammatory effects by controlling immune cell profile and also, promote restoration of damaged stem cell niches—the bone marrow—by repopulating BMSCs or potentiating its paracrine ability. This study aimed to explore the therapeutic effects of systemically injected SP on ovariectomy (OVX)-induced osteoporosis.

Resultantly, SP injection obviously blocked OVX-induced impairment of bone microarchitecture and reduction of the mineral density. In osteoporotic condition, SP could ameliorate chronic inflammation by promoting Treg cell polarization and inhibiting the development of osteoclastogenic Th17 cells. Moreover, SP could rejuvenate stem cell and enable stem cells to repopulate and differentiate into osteoblast.

Collectively, our study strongly suggests that SP treatment can block osteoporosis and furthermore, SP treatment provides therapeutic effect on chronic disease with inflammation and stem cell dysfunction.

SP prevents T2DM complications by immunomodulation

Type 2 diabetic mellitus (T2DM) is characterized by systemic inflammation and insulin resistance due to obesity, and this leads to critical complications, including retinopathy and nephropathy. This study explored the therapeutic effect of substance-p (SP), a neuropeptide, on T2DM progression and its complications. To examine whether SP affects glucose metabolism, lipid metabolism, systemic inflammation, and retinopathy, Otsuka Long-Evans Tokushima Fatty rats (OLETF, 27 weeks old) with chronic inflammation, obesity, and impaired bone marrow stem cell pool was selected. SP was intravenously injected and its effect was evaluated at 2 and 4 weeks after the SP injection. OLETF had typical symptoms of T2DM, including obesity, chronic inflammation, and poor glycemic control. However, SP treatment inhibited the body-weight gain and reduced circulating levels of free fatty acid, cholesterol, and triglyceride, ameliorating the obese environment. SP could suppress inflammation and rejuvenate bone marrow stem cell in OLETF rats. SP-mediated metabolic/immunological change could resolve hyperglycemia and insulin resistance. Histopathological analysis confirmed that SP treatment alleviated the dysfunction of target tissue with insulin resistance. OLETF rats have retinal damage from 27 weeks of age, which was reliably aggravated at 31 weeks. However, SP treatment could restore the damaged retina, sustaining its structure similarly to that of non-diabetic rats. In conclusion, systemic application of SP is capable contribute to the inhibition of the progression of T2DM and diabetic retinopathy.

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.

Substance P Mediates Estrogen Modulation Proinflammatory Cytokines Release in Intervertebral Disc

Intervertebral disc degeneration (IDD) is a main contributor to low back pain. A close relationship exists between inflammation and pain. Estrogen can affect inflammation and may play a crucial role in IDD and pain. Substance P (SP) can also regulate the expression of pro-inflammatory cytokines in intervertebral disc (IVD). This study aimed to investigate the potential role of SP in estrogen regulation of IDD. Nine-week-old C57BL/6 female mice were divided into four groups as follows: sham surgery (sham), ovariectomy (OVX), ovariectomy plus estrogen replacement therapy (ERT) group (OVX+E2), and ovariectomy, ERT plus neurokinin 1 receptor (NK1R) agonist (OVX+E2+G). Serum E2, body, and uterus weight were recorded. Immunohistochemistry study and quantitative real-time PCR were used for SP, NK1R, IL-1β, IL-6, and TNF-α examination and comparison in IVD at protein and gene levels. After OVX, the gene and protein expression of TNF-α, IL-1β, IL-6, SP, and NK1R in NP cells significantly increased compared with the sham group. ERT can reverse these impacts. ERT plays anti-inflammatory and anti-hyperalgesic roles in IDD of OVX mice. The estrogen-induced changes of the pro-inflammatory cytokines, TNF-α, IL-1β, and IL-6, are significantly inhibited by NK1R agonists. SP may be a mediator of estrogen regulating pro-inflammatory factors in IDD. Estrogen may affect IVD inflammation through two ways: one is to directly affect the level of pro-inflammatory cytokines and the other is by means of modulation of SP.

NF-κB Phosphorylation Inhibition Prevents Articular Cartilage Degradation in Osteoarthritis Rats via 2-Aminoquinoline

Background

Osteoarthritis is a chronic degenerative disease of the joints that is common in older people worldwide. The characteristic features of osteoarthritis include cartilage degradation, synovitis, and remodelling of subchondral bone. The present study investigated the effect of 2-aminoquinoline on knee articular cartilage degradation in an osteoarthritis rat model.

Material/Methods

The rat model of osteoarthritis was established in Wistar rats by intra-articular injection of monosodium iodoacetate. The rats were randomly divided into 6 groups of 10 rats each: a normal control group, an untreated group, and 4 (5, 10, 15 and 20 mg/kg) treatment groups. The rats in treatment groups received 5, 10, 15, or 20 mg/kg doses of 2-aminoquinoline on day 2 of monosodium iodoacetate injection.

Results

The 2-aminoquinoline treatment of monosodium iodoacetate-injected rats markedly decreased weight-bearing asymmetry, inhibited edema formation, and improved paw withdrawal thresholds. The expression of inflammatory cytokines was markedly higher in the osteoarthritis rats. Treatment with 2-aminoquinoline led to a significant reduction in inflammatory cytokine expression in osteoarthritis rats in a dose-dependent manner. In osteoarthritis rats, the expressions of prostaglandin E2 (PGE2), matrix metalloproteinase-13 (MMP-13), and substance P were also higher in comparison to the control group. The 2-aminoquinoline treatment supressed PGE2, MMP-13, and substance P levels in osteoarthritis rats. Moreover, the expression of phosphorylated nuclear factor kappaB (p-NF-κB) was markedly higher in the untreated rats. However, activation of NF-κB was downregulated in the osteoarthritis rats by treatment with 2-aminoquinoline.

Conclusions

The present study demonstrated that 2-aminoquinoline prevents articular cartilage damage in osteoarthritis rats through inhibition of inflammatory factors and downregulation of NF-κB activation, suggesting that 2-aminoquinoline would be effective in treatment of osteoarthritis.

Pain and immunity: implications for host defence

Pain is a hallmark of tissue injury, inflammatory diseases, pathogen invasion and neuropathy. It is mediated by nociceptor sensory neurons that innervate the skin, joints, bones, muscles and mucosal tissues and protects organisms from noxious stimuli. Nociceptors are sensitized by inflammatory mediators produced by the immune system, including cytokines, lipid mediators and growth factors, and can also directly detect pathogens and their secreted products to produce pain during infection. Upon activation, nociceptors release neuropeptides from their terminals that potently shape the function of innate and adaptive immune cells. For some pathogens, neuron-immune interactions enhance host protection from infection, but for other pathogens, neuron-immune signalling pathways can be exploited to facilitate pathogen survival. Here, we discuss the role of nociceptor interactions with the immune system in pain and infection and how understanding these pathways could produce new approaches to treat infectious diseases and chronic pain.

Substance P improves MSC-mediated RPE regeneration by modulating PDGF-BB

Stem cells have regenerative potentials that can be used for the treatment of critical and incurable diseases. Age-related macular degeneration (ARMD) and diabetic retinopathy are one of the most severe retinal disorders, which are mostly attributed to impairment of retinal pigmented epithelium (RPE). Thus, restoration of RPE is the main therapeutic approach to prevent the development of ocular diseases, such as ARMD. In this study, we have investigated the role of substance P (SP) on bone marrow mesenchymal stem cell (MSC)-mediated RPE regeneration in vitro. The MSCs were primed with SP followed by the addition of conditioned medium (MSC^SP-CM) to RPE. The effects of MSC^SP-CM on RPE activity was evaluated by assessing viability, proliferation rate, and migration of RPE. Ex vivo long-term culture led to altered cellular characteristics of MSCs by weakening cell viability, cytokine secretion, and differentiation potential. The conditioned medium of early passage MSC (E-MSC^CM) enhanced the RPE viability and migration, whereas the late passage MSC (L-MSC^CM) hardly influenced the RPE activity. SP priming, however, facilitated the inductive effects of MSC, and SP effect was more distinct in the late passage than in the early passage. Moreover, it was revealed that SP could exert its effects by modulating PDGF-BB secretion in the MSCs. Taken together, these results suggested that SP could restore the therapeutic effects of MSCs on retinal diseases by elevating their proliferative and paracrine activities through PDGF-PDGFR signaling in ex vivo culture.

Substance P enhances BMSC osteogenic differentiation via autophagic activation

Bone mesenchymal stem cells (BMSCs) are the most commonly investigated progenitor cells in bone tissue engineering for treating severe bone defects. Strategies for regulating BMSC differentiation fate have received wide attention, in which redox homeostasis plays an important role due to the change in energy metabolism during stem cell differentiation. In the present study, it was observed that autophagic activity was induced along with BMSC osteogenic differentiation and subsequently regulated reactive oxygen species (ROS) generation and the level of osteogenesis. Furthermore, it was also observed that neuropeptide substance P (SP) administration could enhance the autophagic activity in rat BMSCs via the AMPK and mTOR pathways, as well as decreasing ROS generation and promoting osteogenic differentiation. Inhibition of autophagic activity by 3‑MA reversed the effects of SP on ROS and osteogenic levels. The present results indicated that autophagic activity participated in the regulation of differentiation fate of BMSCs and SP could promote osteogenic differentiation by activating autophagy, providing a more precise biological mechanism for its application in bone tissue engineering.

Substance P accelerates wound repair by promoting neovascularization and preventing inflammation in an ischemia mouse model

AIMS

Arterial insufficiency ulcers are frequent complications of peripheral artery disease and infection or long-term neglect of the ulcer can eventually lead to amputation of the affected body part. An ischemic environment, caused by interrupted blood flow, affects the supply of nutrients and elongates the inflammation period, inducing tissue degeneration. Thus, the modulation of neovascularization and inflammation could be an ideal therapeutic strategy for ischemic wound healing. This study aimed to elucidate whether systemically administered substance P (SP) could promote ischemic wound repair in mice by restoring blood perfusion and suppressing inflammation.

MAIN METHODS

The effects of SP were assessed by analyzing wound size, blood flow, epidermal and dermal layer regeneration, vessel formation, and the inflammatory cytokine profiles in a hind-limb ischemia non-clinical mouse model.

KEY FINDINGS

SP-treated mice exhibited dramatically rapid wound healing and restoration of blood flow within the ischemic zone, compared with saline-treated mice. Notably, SP-treated mice showed enhanced pericyte-covered vasculature compared to saline-treated mice. Moreover, anti-inflammatory effects were detected in mice in the SP-treated group, including suppression of inflammation-mediated spleen enlargement, reduction of tumor necrosis factor-alpha, and promotion of circulatory interleukin-10 levels.

SIGNIFICANCE

These results suggest that SP could be a possible therapeutic candidate for patients with peripheral artery disease, including those with ischemic ulcers.

Substance P ameliorates tumor necrosis factor-alpha-induced endothelial cell dysfunction by regulating eNOS expression in vitro

OBJECTIVE

The aim of this study was to explore the beneficial effects of SP on NO production and inflammation-induced vascular endothelium cell death.

METHODS

To mimic the inflammatory environment, TNF-α was treated with HUVECs, and SP was added prior to TNF-α to determine its protective effect. WST-1 assay was performed to detect cell viability. NO level in conditioned medium was measured by Griess Reagent System. The protein level of cleaved caspase-3, eNOS, and phosphorylated Akt was detected by Western blot analysis.

RESULTS

TNF-α declined endothelial cell viability by downregulating Akt and NO production. TNF-α-induced cell death was reliably restored by NO, confirming the requirement of NO for cell survival. By contrast, pretreatment of SP attenuated TNF-α-induced cellular apoptosis, accompanied by an increase in the phosphorylation of Akt, eNOS expression, and NO production. Blockage of NK-1R, phosphorylated Akt or eNOS by CP-96345, A6730, or L-NAME entirely eliminated the effect of SP.

CONCLUSIONS

SP can protect the vascular endothelium against inflammation-induced damage through modulation of the Akt/eNOS/NO signaling pathway.

A Pathophysiological Validation of Collagenase II-Induced Biochemical Osteoarthritis Animal Model in Rabbit

BACKGROUND

Current dilemma working with surgically-induced OA (osteoarthritis) model include inconsistent pathological state due to various influence from surrounding tissues. On the contrary, biochemical induction of OA using collagenase II has several advantageous points in a sense that it does not involve surgery to induce model and the extent of induced cartilage degeneration is almost uniform. However, concerns still exists because biochemical OA model induce abrupt destruction of cartilage tissues through enzymatic digestion in a short period of time, and this might accompany systemic inflammatory response, which is rather a trait of RA (rheumatoid arthritis) than being a trait of OA.

METHODS

To clear the concern about the systemic inflammatory response that might be caused by abrupt destruction of cartilage tissue, OA was induced to only one leg of an animal and the other leg was examined to confirm the presence of systemic degenerative effect.

RESULTS

Although the cartilage tissues were rapidly degenerated during short period of time upon biochemical induction of OA, they did not accompanied with RA-like process based on the histology data showing degeneration of articular cartilage occurred only in the collagenase-injected knee joint. Scoring evaluation data indicated that the cartilage tissues in non-induced joint remained intact. Neutrophil count transiently increase between day 8 and day 16, and there were no significant change in other complete blood count profile showing a characteristics of OA disease.

CONCLUSION

These study shows that biochemically induced cartilage degeneration truly represented uniform and reliable OA state.

Substance P restores normal skin architecture and reduces epidermal infiltration of sensory nerve fiber in TNCB-induced atopic dermatitis-like lesions in NC/Nga mice

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disorder characterized by intense pruritus and eczematous lesion. Substance P (SP) is an 11-amino-acid endogenous neuropeptide that belongs to the tachykinin family and several reports recently have supported the anti-inflammatory and tissue repairing roles of SP.

OBJECTIVE

In this study, we investigated whether SP can improve AD symptoms, especially the impaired skin barrier function, in 2, 4, 6-trinitrochlorobenzene (TNCB)-induced chronic dermatitis of NC/Nga mice or not.

METHOD

AD-like dermatitis was induced in NC/Nga mice by repeated sensitization with TNCB for 5 weeks. The experimental group designations and topical treatments were as follows: vehicle group (AD-VE); SP group (AD-SP); and SP with NK1R antagonist CP99994 (AD-SP-A) group. Histological analysis was performed to evaluate epidermal differentiation, dermal integrity, and epidermal nerve innervation in AD-like lesions. The skin barrier functions and pruritus of NC/Nga mice were evaluated by measuring transepidermal water loss (TEWL) and scratching behavior, respectively.

RESULT

Topical SP treatment resulted in significant down-regulation of Ki67 and the abnormal-type keratins (K) K6, K16, and K17, restoration of filaggrin and claudin-1, marked reduction of TEWL, and restoration of basement membrane and dermal collagen deposition, even under continuous sensitization of low dose TNCB. In addition, SP significantly reduced innervation of itch-evoking nerve fibers, gelatinase activity and nerve growth factor (NGF) expression in the epidermis but upregulated semaphorin-3A (Sema3A) expression in the epidermis, along with reduced scratching behavior in TNCB-treated NC/Nga mice. All of these effects were completely reversed by co-treatment with the NK1R antagonist CP99994. In cultured human keratinocytes, SP treatment reduced expression of TGF-α, but upregulated TGF-β and Sema3A.

CONCLUSION

Topically administered SP can restore normal skin barrier function, reduce epidermal infiltration of itch-evoking nerve fibers in the AD-like skin lesions, and alleviate scratching behavior. Thus, SP may be proposed as a potential medication for chronic dermatitis and AD.

Endogenous Stem Cells in Homeostasis and Aging

In almost all human tissues and organs, adult stem cells or tissue stem cells are present in a unique location, the so-called stem cell niche or its equivalent, continuously replenishing functional differentiated cells. Those endogenous stem cells can be expanded for cell therapeutics using ex vivo cell culture or recalled for tissue repair in situ through cell trafficking and homing. In the aging process, inefficiency in the endogenous stem cell-mediated healing mechanism can emerge from a variety of impairments that accumulate in the processes of stem cell self-renewal, function, differentiation capacity, and trafficking through cell autonomous intrinsic pathways (such as epigenetic alterations) or systemic extrinsic pathways. This review examines the homeostasis of endogenous stem cells, particularly bone marrow stem cells, and their dysregulation in disease and aging and discusses possible intervention strategies. Several systemic pro-aging and rejuvenating factors, recognized in heterochronic parabiosis or premature aging progeroid animal models, are reviewed as possible anti-aging pharmaceutical targets from the perspective of a healthy environment for endogenous stem cells. A variety of epigenetic modifications and chromosome architectures are reviewed as an intrinsic cellular pathway for aging and senescence. A gradual increase in inflammatory burden during aging is also reviewed. Finally, the tissue repair and anti-aging effects of Substance-P, a peptide stimulating stem cell trafficking from the bone marrow and modifying the inflammatory response, are discussed as a future anti-aging target.

Manifestation of atopic dermatitis-like skin in TNCB-induced NC/Nga mice is ameliorated by topical treatment of substance P, possibly through blockade of allergic inflammation

Atopic dermatitis (AD) is a chronic inflammatory skin disorder characterized by intense pruritus and eczematous lesion. In this study, topically applied substance P (SP) significantly alleviated AD-like clinical symptoms in 2, 4, 6-trinitrochlorobenzene (TNCB)-induced dermatitis in NC/Nga mice. This effect was nullified by pretreatment of the neurokinin-1 receptor (NK-1R) antagonist CP99994. SP treatment significantly reduced the infiltration of mast cells and CD3-positive T cells as well as inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and thymic stromal lymphopoietin (TSLP), in AD-like skin lesions and decreased the levels of IgE and thymus and activation-regulated chemokine in serum. This SP-induced alleviation of allergic inflammatory responses was also confirmed as reduced activation in the axillary lymph nodes (aLN) and spleen, suggesting the systemic effect of SP on immune responses in TNCB-induced NC/Nga mice. Furthermore, SP-mediated TSLP reduction was confirmed in human keratinocyte culture under pro-inflammatory TNF-α stimulation. Taken together, these results suggest that topically administered SP may have potential as a medication for atopic dermatitis.

Substance P/dexamethasone-encapsulated PLGA scaffold fabricated using supercritical fluid process for calvarial bone regeneration

Poly(lactic-co-glycolic acid) (PLGA) scaffolds encapsulated with substance P (SP) and dexamethasone (Dex) by the supercritical CO₂ foaming method were fabricated to treat calvarial bone. We compared the release profiles of SP and Dex according to the incorporation methods using encapsulation or dipping. Ninety percent of the SP or Dex molecules in the scaffolds prepared by the encapsulating method were released by day 14 or day 6, respectively. In vivo real-time assays for human mesenchymal stem cell (hMSC) tracking were performed to confirm the MSC recruitment abilities of the scaffolds. The results showed that the optical intensity of the SP-encapsulated group was 2.59 times higher than that of the phosphate-buffered saline group and 1.3 times higher than that of the SP-dipping group. Furthermore, we compared the angiogenesis activity of the scaffolds. In the SP-encapsulated group, 72.9  ±  2.6% of the vessels showed matured features by 1 week, and it increased to 82.0  ±  4.6% after 4 weeks. We implanted the scaffolds into rat calvarial defects. After 24 weeks, SP- and Dex-encapsulated scaffolds showed 67.1% and 26.2% higher bone formation than those of the Dex-encapsulated group and SP-encapsulated group, respectively, and they formed 36.1% more bone volume compared with the SP- and Dex-dipped scaffolds. Consequently, the results of this study suggest that SP- and Dex-encapsulated scaffolds made by the supercritical CO₂ foaming method could be a good treatment modality to treat critical bone defects without cell transplantation by recruiting autologous stem cells and forming new bone tissues. Copyright © 2017 John Wiley & Sons, Ltd.

Substance P Induces HO-1 Expression in RAW 264.7 Cells Promoting Switch towards M2-Like Macrophages

Substance P (SP) is a neuropeptide that mediates many physiological as well as inflammatory responses. Recently, SP has been implicated in the resolution of inflammation through induction of M2 macrophages phenotype. The shift between M1-like and M2-like, allowing the resolution of inflammatory processes, also takes place by means of hemeoxygenase-1 (HO-1). HO-1 is induced in response to oxidative stress and inflammatory stimuli and modulates the immune response through macrophages polarisation. SP induces HO-1 expression in human periodontal ligament (PDL), the latter potentially plays a role in cytoprotection. We demonstrated that SP promotes M2-like phenotype from resting as well as from M1 macrophages. Indeed, SP triggers the production of interleukine-10 (IL-10), interleukine-4 (IL-4) and arginase-1 (Arg1) without nitric oxide (NO) generation. In addition, SP increases HO-1 expression in a dose- and time-dependent manner. Here we report that SP, without affecting cell viability, significantly reduces the production of pro-inflammatory cytokines and enzymes, such as tumor necrosis factor-alpha (TNF-α), interleukine-6 (IL-6), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and ameliorates migration and phagocytic properties in LPS-stimulated RAW 264.7 cells. M2-like conversion required retention of NF-κB p65 into the cytoplasm and HO-1 induced expression. Silencing of the HO-1 mRNA expression reversed the induction of pro-inflammatory cytokines in RAW 264.7 stimulated by LPS and down-regulated anti-inflammatory hallmarks of M2 phenotype. In conclusion, our data show that SP treatment might be associated with anti-inflammatory effects in LPS-stimulated RAW 264.7 cells by suppressing NF-κB activation and inducing HO-1 expression.

Substance-P alleviates dextran sulfate sodium-induced intestinal damage by suppressing inflammation through enrichment of M2 macrophages and regulatory T cells

Intestinal inflammation alters immune responses in the mucosa and destroys colon architecture, leading to serious diseases such as inflammatory bowel disease (IBD). Thus, regulation of inflammation is regarded as the ultimate therapy for intestinal disease. Substance-P (SP) is known to mediate proliferation, migration, and cellular senescence in a variety of cells. SP was found to mobilize stem cells from bone marrow to the site of injury and to suppress inflammatory responses by inducing regulatory T cells (Tregs) and M2 macrophages. In this study, we explored the effects of SP in a dextran sodium sulfate (DSS)-induced intestine damage model. The effects of SP were evaluated by analyzing crypt structures, proliferating cells within the colon, cytokine secretion profiles, and immune cells population in the spleen/mesenteric lymph nodes in vivo. DSS treatment provoked an inflammatory response with loss of crypts in the intestines of experimental mice. This response was associated with high levels of inflammatory cytokines such as TNF-α and IL-17, and low levels of Tregs and M2 macrophages, leading to severely damaged tissue structure. However, SP treatment inhibited inflammatory responses by modulating cytokine production as well as the balance of Tregs/Th 17 cells and the M1/M2 transition in lymphoid organs, leading to accelerated tissue repair. Collectively, our data indicate that SP can promote the regeneration of tissue following damage by DSS treatment, possibly by modulating immune response. Our results propose SP as a candidate therapeutic for intestine-related inflammatory diseases.

Blocking of the P2X7 receptor inhibits the activation of the MMP-13 and NF-κB pathways in the cartilage tissue of rats with osteoarthritis

P2X purinoceptor 7 (P2X7) receptor (P2X7R) is known to play a significant role in inflammation and pain-causing diseases, including osteoarthritis (OA). However, the mechanisms of action of P2X7R and its role in OA remain unclear. The articular cartilage is the crucial region in which pathological changes occur in OA, involving the dysregulation of degradation and maintenance mechanisms. In this study, we aimed to reveal the molecular mechanisms of action of P2X7R in articular cartilage in OA-induced pain and inflammation by using AZD9056, an antagonist of P2X7R. We created an animal model of OA by using Wistar rats administered (by intra-articular injection) monosodium iodoacetate (MIA), and the rats with OA were then treated with the P2X7R antagonist, AZD9056. We found that treatment with AZD9056 exerted pain-relieving and anti-inflammatory effects. Importantly, we found that the upregulated expression of interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α), matrix metalloproteinase-13 (MMP-13), substance P (SP) and prostaglandin E2 (PGE2) which was induced by MIA in cartilage tissues was reversed by AZD9056. Western blot analysis was used to examine the expression of inhibitor of nuclear factor-κB (NF-κB) kinase (IKK)α, IKKβ, inhibitor of NF-κB (IκB)α, NF-κB p65 and their phosphorylation forms; they were found to be significantly increased in the knee cartilage tissues from rats with OA; however, opposite effects were observed by the injection of AZD9056. These results implied that P2X7R was associated with the activation of the NF-κB pathway in the development of OA. Our results also revealed that helenalin, an NF-κB pathway inhibitor, decreased the expression of P2X7R, IL-1β, IL-6, TNF-α, SP, PGE2 and MMP-13, which was induced by MIA, in the knee cartilage tissues of rats with OA. On the whole, our findings suggest that P2X7R regulates the MMP-13 and NF-κB pathways in cartilage tissue and mediate OA-induced pain and inflammation.

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.

Covalent immobilization of stem cell inducing/recruiting factor and heparin on cell-free small-diameter vascular graft for accelerated in situ tissue regeneration

The development of cell-free vascular grafts has tremendous potential for tissue engineering. However, thrombus formation, less-than-ideal cell infiltration, and a lack of growth potential limit the application of electrospun scaffolds for in situ tissue-engineered vasculature. To overcome these challenges, here we present development of an acellular tissue-engineered vessel based on electrospun poly(L-lactide-co-ɛ-caprolactone) scaffolds. Heparin was conjugated to suppress thrombogenic responses, and substance P (SP) was immobilized to recruit host cells. SP was released in a sustained manner from scaffolds and recruited human bone marrow-derived mesenchymal stem cells. The biocompatibility and biological performance of the grafts were evaluated by in vivo experiments involving subcutaneous scaffold implantation in Sprague-Dawley rats (n = 12) for up to 4 weeks. Histological analysis revealed a higher extent of accumulative host cell infiltration, neotissue formation, collagen deposition, and elastin deposition in scaffolds containing either SP or heparin/SP than in the control groups. We also observed the presence of a large number of laminin-positive blood vessels, von Willebrand factor (vWF(+) ) cells, and alpha smooth muscle actin-positive cells in the explants containing SP and heparin/SP. Additionally, SP and heparin/SP grafts showed the existence of CD90(+) and CD105(+) MSCs and induced a large number of M2 macrophages to infiltrate the graft wall compared with that observed with the control group. Our cell-free grafts could enhance vascular regeneration by endogenous cell recruitment and by mediating macrophage polarization into the M2 phenotype, suggesting that these constructs may be a promising cell-free graft candidate and are worthy of further in vivo evaluation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1352-1371, 2016.

Therapeutic effects of neuropeptide substance P coupled with self-assembled peptide nanofibers on the progression of osteoarthritis in a rat model

Osteoarthritis (OA) is a progressively degenerative disease that is accompanied by articular cartilage deterioration, sclerosis of the underlying bone and ultimately joint destruction. Although therapeutic medicine and surgical treatment are done to alleviate the symptoms of OA, it is difficult to restore normal cartilage function. Mesenchymal stem cell (MSC) transplantation is one of the therapeutic trials for treating OA due to its potential, and many researchers have recently reported on the effects of MSCs associated with OA therapy. However, cell transplantation has limitations including low stem cell survival rates, limited stem cell sources and long-term ex vivo culturing. In this study, we evaluated the efficacy of neuropeptide substance P coupled with self-assembled peptide hydrogels in a rat knee model to prevent OA by mobilizing endogenous MSCs to the defect site. To assess the effect of the optimal concentration of SP, varying concentrations of bioactive peptides (substance P (SP) with self-assembled peptide (SAP)) were used to treat OA. OA was induced by unilateral anterior cruciate and medial collateral ligament transection of the knee joints. Forty rats were randomly allocated into 5 groups: SAP-0.5SP (17.5 μg of SP), SAP-SP group (35 μg of SP), SAP-2SP group (70 μg of SP), SAP-SP-MSC group, and control group. At 2 weeks post-surgical induction of OA, each mixture was injected into the joint cavity of the left knee. Histologic examination, immunofluorescence staining, quantitative real time-polymerase chain reaction and micro-computed tomography analysis were done at 6 weeks post-surgical induction. As shown by our results, the SAP-SP hydrogel accelerated tissue regeneration by anti-inflammatory modulation shown by an anti-inflammation test using dot-blot in vitro. Additionally, the treatment of OA in the SAP-SP group showed markedly improved cartilage regeneration through the recruitment of MSCs. Thus, these cells could be infiltrating into the defect site for the regeneration of OA defects. In addition, from the behavioral studies on the rats, the number of rears significantly increased 2 and 4 weeks post-injection in all the groups. Our results show that bioactive peptides may have clinical potential for inhibiting the progression of OA as well as its treatment by recruiting autologous stem cells without cell transplantation.

Understanding the Mysterious M2 Macrophage through Activation Markers and Effector Mechanisms

The alternatively activated or M2 macrophages are immune cells with high phenotypic heterogeneity and are governing functions at the interface of immunity, tissue homeostasis, metabolism, and endocrine signaling. Today the M2 macrophages are identified based on the expression pattern of a set of M2 markers. These markers are transmembrane glycoproteins, scavenger receptors, enzymes, growth factors, hormones, cytokines, and cytokine receptors with diverse and often yet unexplored functions. This review discusses whether these M2 markers can be reliably used to identify M2 macrophages and define their functional subdivisions. Also, it provides an update on the novel signals of the tissue environment and the neuroendocrine system which shape the M2 activation. The possible evolutionary roots of the M2 macrophage functions are also discussed.

Increasing expression of substance P and calcitonin gene-related peptide in synovial tissue and fluid contribute to the progress of arthritis in developmental dysplasia of the hip

INTRODUCTION

Developmental dysplasia of the hip (DDH) is a common musculoskeletal disorder that has pain and loss of joint function as major pathological features. In the present study, we explored the mechanisms of possible involvement and regulation of substance P (SP) and calcitonin gene-related peptide (CGRP) in the pathological and inflammatory processes of arthritis in DDH.

METHODS

Blood, synovial tissue and fluid samples were collected from patients diagnosed with different severities of DDH and from patients with femoral neck fracture. Levels of SP, CGRP and inflammatory cytokines in synovium and synovial fluid (SF) in the different groups were evaluated by immunohistochemistry, real-time PCR and enzyme-linked immunosorbent assay (ELISA). Correlations between neuropeptides and inflammatory cytokines in SF were evaluated by partial correlation analysis. The proinflammatory effects of SP and CGRP on synoviocytes obtained from patients with moderate DDH were investigated in vitro by real-time PCR and ELISA. The mechanisms of those effects were evaluated by Western blot analysis and nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) DNA binding assay.

RESULTS

Significantly increased levels of neuropeptides and inflammatory cytokines were observed in synovium and SF from patients in the severe DDH group compared with the moderate DDH and control groups. In moderate DDH samples, SP in SF correlated with tumor necrosis factor (TNF)-α, and CGRP in SF correlated with TNF-α and interleukin (IL)-10. In the severe DDH group, SP in SF correlated with interleukin (IL)-1β, TNF-α and IL-10. CGRP in SF correlated with TNF-α. Additionally, SP might have had obvious proinflammatory effects on synoviocytes through the activation of NF-κB.

CONCLUSIONS

The upregulation of SP and CGRP in synovium and SF might participate in the inflammatory process of arthritis in DDH. The activation of the NF-κB pathway seems indispensable in the proinflammatory effect of SP on synoviocytes. This original discovery may indicate a potential clinical drug target and the development of innovative therapies for DDH.