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

Substance P concentration is associated with the inflammatory response and pain perception in patients with chronic pain in peripheral artery disease

<b>Introduction:</b> Previous studies indicate a significant role of the inflammatory response in the etiopathogenesis of peripheral artery disease (PAD) and chronic pain (CP).<b>Aim:</b> The aim of the study was to determine the relationship between the concentration of SP and the level/concentration of inflammatory mediators (pro-inflammatory cytokines, positive and negative acute phase protein, anti-inflammatory cytokines) and pain intensity in people suffering from chronic pain (CP) in the course of PAD.<b>Material and methods:</b> We examined 187 patients of the Department of Vascular Surgery. As many as 92 patients with PAD and CP (study group) were compared to 95 patients with PAD without CP (control group). The relationship between SP and the level/concentration of fibrinogen, C-reactive protein (CRP), antithrombin III (AT), serum albumin, interleukin 10 (IL-10), tumor necrosis factor alpha (TNF-α) and pain intensity (Numeric Rating Scale; NRS) was analyzed. Statistical analysis was performed using the R program, assuming the level of statistical significance of α = 0.05.<b>Results:</b> Patients with CP had significantly higher levels of fibrinogen (P < 0.001), CRP (P < 0.001), SP (P < 0.001), IL-10 (P < 0.001), and lower serum albumin levels (P < 0.023). Higher SP concentration was associated with higher levels of IL-10, CRP, and pain intensity. In both groups, SP concentration correlated negatively with the level of fibrinogen (P < 0.001) as well as with albumin in the control group (P < 0.001).<b>Conclusions:</b> Thus, there is a relationship between the concentration of SP and fibrinogen, along with CRP, IL-10, and the intensity of pain in people suffering from CP in the course of PAD, and the level of albumin in the group without CP.

Trigeminal nerve stimulation: a current state-of-the-art review

Nearly 5 decades ago, the effect of trigeminal nerve stimulation (TNS) on cerebral blood flow was observed for the first time. This implication directly led to further investigations and TNS' success as a therapeutic intervention. Possessing unique connections with key brain and brainstem regions, TNS has been observed to modulate cerebral vasodilation, brain metabolism, cerebral autoregulation, cerebral and systemic inflammation, and the autonomic nervous system. The unique range of effects make it a prime therapeutic modality and have led to its clinical usage in chronic conditions such as migraine, prolonged disorders of consciousness, and depression. This review aims to present a comprehensive overview of TNS research and its broader therapeutic potentialities. For the purpose of this review, PubMed and Google Scholar were searched from inception to August 28, 2023 to identify a total of 89 relevant studies, both clinical and pre-clinical. TNS harnesses the release of vasoactive neuropeptides, modulation of neurotransmission, and direct action upon the autonomic nervous system to generate a suite of powerful multitarget therapeutic effects. While TNS has been applied clinically to chronic pathological conditions, these powerful effects have recently shown great potential in a number of acute/traumatic pathologies. However, there are still key mechanistic and methodologic knowledge gaps to be solved to make TNS a viable therapeutic option in wider clinical settings. These include bimodal or paradoxical effects and mechanisms, questions regarding its safety in acute/traumatic conditions, the development of more selective stimulation methods to avoid potential maladaptive effects, and its connection to the diving reflex, a trigeminally-mediated protective endogenous reflex. The address of these questions could overcome the current limitations and allow TNS to be applied therapeutically to an innumerable number of pathologies, such that it now stands at the precipice of becoming a ground-breaking therapeutic modality.

An investigation on the changes of serum CCK-8, substance P, and 5-HT in patients with post-stroke insomnia

BACKGROUND

At present, the pathogenesis of post-stroke insomnia (PSI) is still inconclusive.

OBJECTIVE

To explore the changes and significance of serum cholecystokinin-8 (CCK-8), substance P (SP), and 5-hydroxytryptamine (5-HT) in patients with PSI.

METHODS

Ninety-one patients with stroke were selected as the research subjects, and according to the score of the Athens Insomnia Scale (AIS), they were divided into the insomnia group and the non-insomnia group. The serum levels of CCK-8, SP, and 5-HT in the two groups were compared to explore their relationships with PSI.

RESULTS

Among the 91 patients, 56 were in the insomnia group and 35 were in the non-insomnia group, and the incidence of insomnia was 61.5%. There was no significant difference in the serum levels of CCK-8, SP, and 5-HT between the two groups (P= 0.696, 0.980, and 0.809, respectively). One-way analysis of variance showed that there was no significant correlation between the serum levels of CCK-8, SP, 5-HT, and the AIS score (P= 0.7393, 0.9581, and 0.5952, respectively).

CONCLUSION

The incidence of PSI was relatively high, but it could not be proved that CCK-8, SP, and 5-HT were involved in the pathogenesis of PSI. There might exist other neurotransmitters involved in the pathophysiological process of PSI, which should be further explored.

Substance P-Mediated Vascular Protection Ameliorates Bone Loss

Estrogen deficiency causes bone loss via diverse pathological cellular events. The involvement of the vasculature in bone formation has been widely studied, and type H vasculature has been found to be closely related to bone healing. Ovariectomy- (OVX-) induced estrogen deficiency reduces type H vessel density and promotes reduction of bone density. Analysis of early events after OVX showed that estrogen deficiency preferentially induces oxidative stress, which might provoke endothelial dysfunction and reduce angiogenic factors systemically and locally. The instability of the vascular potential is expected to promote bone loss under estrogen deficiency. Substance P (SP) is an endogenous neuropeptide that controls inflammation and prevents cell death under pathological conditions. SP can elevate nitric oxide production in endothelial cells and inhibit endothelial dysfunction. This study is aimed at investigating the preventive effects of systemically injected SP on OVX-induced vascular loss and osteoporosis onset. SP was systemically administered to OVX rats twice a week for 4 weeks, immediately after OVX induction. OVX conditions could decrease antioxidant enzyme activity, type H vessels, and angiogenic growth factors in the bone marrow, followed by inflammation and bone loss. However, pretreatment with SP could block type H vessel loss, accompanied by the enrichment of nitric oxide and sustained angiogenic factors. SP-mediated early vascular protection inhibits bone density reduction. Altogether, this study suggests that early administration of SP can block osteoporosis development by modulating oxidative stress and protecting the bone vasculature and angiogenic paracrine potential at the initial stage of estrogen deficiency.

IL-1β/NF-κB signaling inhibits IGF-1 production via let-7f-5p in dendritic epidermal T cells

Dendritic epidermal T cells (DETCs) are the main source of insulin-like growth factor-1 (IGF-1) in epidermal tissue, which promote re-epithelialization and wound healing. In refractory wounds, IL-1β has been shown to activate NF-κB and suppress IGF-1 expression in DETCs. Nevertheless, the underlying mechanisms remain unclear. In this study, chromatin immunoprecipitation analysis revealed that IL-1β did not inhibit NF-κB binding to IGF-1 promoter, indicating that IL-1β/NF-κB may suppress IGF-1 expression by alternative mechanisms. MiRNAs negatively regulate gene expression predominantly by base pairing to the 3' untranslation region (UTR) of target mRNAs. Let-7f-5p, miR-1a-3p, and miR-98-5p have been identified as IGF-1-specific miRNAs that can bind directly to the 3'UTR of IGF-1 mRNA and dysregulate IGF-1 mRNA and protein levels. In IL-1β-treated epidermis around wounds or DETCs in vitro, NF-κB promoted the expression of let-7f-5p, and IGF-1 expression was impeded via NF-κB/let-7f-5p pathway. As pre-let-7f-5p, let-7f-1 is located in the 3'UTR of LOC118568094, and let-7f-2 is located in the intron of HUWE1. We discovered that NF-κB p65 bound to the promoters of LOC118568094 and HUWE1 to accelerate let-7f-5p expression, but NF-κB p65 did not affect the methylation levels of LOC118568094 and HUWE1 CpG islands. Injections of Let-7f-5p antagomir into IL-1β-treated and ischemic wound margins restored IGF-1 secretion in DETCs and promoted wound healing. In conclusion, we demonstrated that NF-κB signaling pathway activated by IL-1β could increase let-7f-5p expression to inhibit IGF-1 production in DETCs and delay wound healing. And let-7f-5p antagomir utilized in wound margin could effectively promote refractory wound healing.

Negative Pressure Wound Therapy Promotes Wound Healing by Inhibiting Inflammation in Diabetic Foot Wounds: A Role for NOD1 Receptor

Aims: Diabetic foot results in frequent amputation and quality-of-life reduction in diabetes population. These lesions are featured by a prolonged and exaggerated inflammation with a significant impairment in local bacterial invasion. Negative pressure wound therapy (NPWT) attenuates hyperinflammation in the healing of diabetic foot wounds, but the potential mechanism of NPWT down-regulated inflammatory reaction still remains elusive. This study aims to explore the inflammatory signaling involved in the effect of NPWT on diabetic ulcer. Methods: Thirty patients with diabetic foot ulceration were divided into NPWT group (treated with NPWT, n = 10), NPWT + FK565 group (treated with NPWT combined with FK565 which is NOD1 receptor ligand, n = 10) and control group (n = 10). After two weeks treatment, samples were harvested and analyzed by histochemistry for infiltration of inflammatory cells, immunofluorescence stain for NOD1, western blotting for NOD1, RIP2 (Receptor interacting protein 2), IL-1β, TAK1 (Transforming growth factor-β-activated kinase1), p65 and real time-PCR for expression of NOD1 and RIP2. Results: NPWT could notably accelerate the diabetic wound healing through alleviating inflammatory reaction. The immunofluorescence analysis results revealed that NOD1 was mainly expressed in the cytoplasm and noticeably decreased after the NPWT treatment. And NPWT obviously decreased both the mRNA and protein level of NOD1 and RIP2. Moreover, The protein expression of IL-1β, TAK1 and p65 in the NPWT-group were significant decreased. Conclusion: NPWT effectively promotes wound healing by suppressing the wound inflammation in diabetic foot, which is mediated at least in part by suppression of NOD1 receptor.

A novel photosynthetic biologic topical gel for enhanced localized hyperoxygenation augments wound healing in peripheral artery disease

Peripheral artery disease and the associated ischemic wounds are substantial causes of global morbidity and mortality, affecting over 200 million people worldwide. Although advancements have been made in preventive, pharmacologic, and surgical strategies to treat this disease, ischemic wounds, a consequence of end-stage peripheral artery disease, remain a significant clinical and economic challenge. Synechococcus elongatus is a cyanobacterium that grows photoautotrophically and converts carbon dioxide and water into oxygen. We present a novel topical biologic gel containing S. elongatus that provides oxygen via photosynthesis to augment wound healing by rescuing ischemic tissues caused by peripheral artery disease. By using light rather than blood as a source of energy, our novel topical therapy significantly accelerated wound healing in two rodent ischemic wound models. This novel topical gel can be directly translated to clinical practice by using a localized, portable light source without interfering with patients' daily activities, demonstrating potential to generate a paradigm shift in treating ischemic wounds from peripheral artery disease. Its novelty, low production cost, and ease of clinical translatability can potentially impact the clinical care for millions of patients suffering from peripheral arterial disease.

Regulation of Carcinogenesis by Sensory Neurons and Neuromediators

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.

The sustained PGE2 release matrix improves neovascularization and skeletal muscle regeneration in a hindlimb ischemia model

BACKGROUND

The promising therapeutic strategy for the treatment of peripheral artery disease (PAD) is to restore blood supply and promote regeneration of skeletal muscle regeneration. Increasing evidence revealed that prostaglandin E₂ (PGE₂), a lipid signaling molecule, has significant therapeutic potential for tissue repair and regeneration. Though PGE₂ has been well reported in tissue regeneration, the application of PGE₂ is hampered by its short half-life in vivo and the lack of a viable system for sustained release of PGE₂.

RESULTS

In this study, we designed and synthesized a new PGE₂ release matrix by chemically bonding PGE₂ to collagen. Our results revealed that the PGE₂ matrix effectively extends the half-life of PGE₂ in vitro and in vivo. Moreover, the PGE₂ matrix markedly improved neovascularization by increasing angiogenesis, as confirmed by bioluminescence imaging (BLI). Furthermore, the PGE₂ matrix exhibits superior therapeutic efficacy in the hindlimb ischemia model through the activation of MyoD1-mediated muscle stem cells, which is consistent with accelerated structural recovery of skeletal muscle, as evidenced by histological analysis.

CONCLUSIONS

Our findings highlight the chemical bonding strategy of chemical bonding PGE₂ to collagen for sustained release and may facilitate the development of PGE₂-based therapies to significantly improve tissue regeneration.

The Regenerative Potential of Substance P

Wound healing is a highly coordinated process which leads to the repair and regeneration of damaged tissue. Still, numerous diseases such as diabetes, venous insufficiencies or autoimmune diseases could disturb proper wound healing and lead to chronic and non-healing wounds, which are still a great challenge for medicine. For many years, research has been carried out on finding new therapeutics which improve the healing of chronic wounds. One of the most extensively studied active substances that has been widely tested in the treatment of different types of wounds was Substance P (SP). SP is one of the main neuropeptides released by nervous fibers in responses to injury. This review provides a thorough overview of the application of SP in different types of wound models and assesses its efficacy in wound healing.

Prognostic Significance of Substance P/Neurokinin 1 Receptor and Its Association with Hormonal Receptors in Breast Carcinoma

Expression and immunolocalization of Substance P (SP)/Neurokinin-1 Receptor (NK-1R) in breast carcinoma (BC) patients and its association with routine proliferative markers (ER, PR, HER2/neu, and Ki-67) were evaluated. A cross-sectional study was performed on 34 cases of BC. There were 23 cases of group A (grade III), 8 of group B (grade II), and only 3 cases of group C (grade I). All samples were then processed for SP and NK-1R immunohistochemistry for few cases. 14/23 cases (61%) of group A, 7/8 cases (88%) of group B, and 2/3 (67%) cases of group C were SP positive. Overall, strong staining (≥10% tumor cells), labeled as "+3," was observed in 9/14 (64.2%) cases of group A and 1/8 (12.5%) cases of group B. Moderate staining labelled as "+2" (in ≥10% tumor cells) was observed in 3/14 (21.4%) cases of group A and 4/8 (50%) cases of group B. Weak positive staining "+1" was observed in only 2/14 (14.28%) cases of group A, 2/8 (25%) cases of group B, and all 2/2 (100%) cases of group C. SP and NK-1R are overexpressed in breast carcinomas, and there is significant association between the grade of tumor and their overexpression.

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.

Substance-P Inhibits Cardiac Microvascular Endothelial Dysfunction Caused by High Glucose-Induced Oxidative Stress

Diabetes is characterized by high glucose (HG) levels in the blood circulation, leading to exposure of the vascular endothelium to HG conditions. Hyperglycemia causes oxidative stress via excessive reactive oxygen species (ROS) production in the endothelium, which leads to cellular dysfunction and the development of diabetic vascular diseases. Substance-P (SP) is an endogenous peptide involved in cell proliferation and migration by activating survival-related signaling pathways. In this study, we evaluated the role of SP in cardiac microvascular endothelial cells (CMECs) in HG-induced oxidative stress. CMECs were treated with diverse concentrations of glucose, and then the optimal dose was determined. Treatment of CMECs with HG reduced their viability and induced excessive ROS secretion, inactivation of PI3/Akt signaling, and loss of vasculature-forming ability in vitro. Notably, HG treatment altered the cytokine profile of CMECs. However, SP treatment inhibited the HG-mediated aggravation of CMECs by restoring viability, free radical balance, and paracrine potential. SP-treated CMECs retained the capacity to form compact and long stretching-tube structures. Collectively, our data provide evidence that SP treatment can block endothelial dysfunction in hyperglycemia and suggest the possibility of using SP for treating diabetic complications as an antioxidant.

Neuropeptides, Inflammation, Biofilms, and diabetic Foot Ulcers

A diabetic foot ulcer (DFU) is a serious complication in patients with diabetes mellitus (DM). A DFU is the most common cause of non-traumatic limb amputation, and patients with DFUs have increased mortality rates within 5 years after amputation. DFUs also increase the risk of cardiovascular and cerebrovascular diseases; therefore, with the increasing incidence and prevalence of diabetic foot wounds, DFUs are gradually becoming a major public health problem. The pathophysiology of DFUs is complicated and remains unclear. In recent years, many studies have demonstrated that the pathophysiology of DFUs is especially associated with neuropeptides, inflammation, and biofilms. Neuropeptides, especially substance P (SP) and calcitonin gene-related peptide (CGRP), play an important role in wound healing. SP and CGRP accelerate the healing of cutaneous wounds by promoting neovascularization, inhibiting the release of certain proinflammatory chemokines, regulating macrophage polarization, and so on. However, the expression of SP and CGRP was downregulated in DM and DFUs. DFUs are characterized by a sustained inflammatory phase. Immune cells such as neutrophils and macrophages are involved in the sustained inflammatory phase in DFUs by extracellular traps (NETs) and dysregulated macrophage polarization, which delays wound healing. Furthermore, DFUs are at increased risk of biofilm formation. Biofilms disturb wound healing by inducing a chronic inflammatory response, inhibiting macrophage phagocytosis and keratinocyte proliferation migration, and transferring antimicrobial resistance genes. To understand the relationships among neuropeptides, inflammation, biofilms, and DFUs, this review highlights the recent scientific advances that provide possible pathophysiological insights into the delayed healing of DFUs.

Substance P blocks β-aminopropionitrile-induced aortic injury through modulation of M2 monocyte-skewed monocytopoiesis

Aortic injuries, including aortic aneurysms and dissections, are fatal vascular diseases with distinct histopathological features in the aortic tissue such as inflammation-induced endothelial dysfunction, infiltration of immune cells, and breakdown of the extracellular matrix. Few treatments are available for treating aortic aneurysms and dissections; thus, basic and clinical studies worldwide have been attempted to inhibit disease progression. Substance P (SP) exerts anti-inflammatory effects and promotes restoration of the damaged endothelium, leading to vasculature protection and facilitation of tissue repair. This study was conducted to explore the protective effects of systemically injected SP on thoracic aortic injury (TAI). A TAI animal model was induced by orally administering β-aminopropionitrile to rats for 6 weeks. β-aminopropionitrile blocked crosslinking ECM in aorta to cause structural alteration with inflammation within 1 week and then, induced aortic dissection within 4 weeks of initiating treatment, leading to mortality within 6 weeks. Treatment of TAI rats with SP-induced anti-inflammatory responses systemically and locally, possibly by enriching anti-inflammatory M2 monocytes in the spleen and peripheral blood at early phase of aortic injury due to β-aminopropionitrile. SP-induced immune suppression finally prevented the development of aortic dissection by limiting inflammation-mediated aortic destruction. Taken together, these results suggest that SP treatment can block aortic injury by controlling the immune-cell profile and suppressing proinflammatory responses during the initial stage of vascular disease progression.

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.

Substance-P Restores Cellular Activity of ADSC Impaired by Oxidative Stress

Oxidative stress induces cellular damage, which accelerates aging and promotes the development of serious illnesses. Adipose-derived stem cells (ADSCs) are novel cellular therapeutic tools and have been applied for tissue regeneration. However, ADSCs from aged and diseased individuals may be affected in vivo by the accumulation of free radicals, which can impair their therapeutic efficacy. Substance-P (SP) is a neuropeptide that is known to rescue stem cells from senescence and inflammatory attack, and this study explored the restorative effect of SP on ADSCs under oxidative stress. ADSCs were transiently exposed to H2O2, and then treated with SP. H2O2 treatment decreased ADSC cell viability, proliferation, and cytokine production and this activity was not recovered even after the removal of H2O2. However, the addition of SP increased cell viability and restored paracrine potential, leading to the accelerated repopulation of ADSCs injured by H2O2. Furthermore, SP was capable of activating Akt/GSK-3β signaling, which was found to be downregulated following H2O2 treatment. This might contribute to the restorative effect of SP on injured ADSCs. Collectively, SP can protect ADSCs from oxidant-induced cell damage, possibly by activating Akt/GSK-3β signaling in ADSCs. This study supports the possibility that SP can recover cell activity from oxidative stress-induced dysfunction.

Anti-Aging Potential of Substance P-Based Hydrogel for Human Skin Longevity

Skin aging is generally caused by a decline in the components of the extracellular matrix (e.g., collagen and elastin) and due to inflammatory phenomena. Many growth factors and peptides with cell-growth and collagen-synthesis activities have shown promise in their application in anti-aging materials. However, the effect of collagen production, without anti-inflammatory effect, and skin penetration may not be enough for their use in anti-aging agents. Previously, we reported a substance P (SP)-based hydrogel (SP gel) that had potential wound-healing activities via induction of skin cell regeneration and collagen synthesis. Here, we analyzed the anti-aging activities and skin absorption effects of SP gel to extend its characterization. Toxicity tests, performed on human dermal fibroblasts (HDFs) and on a reconstructed 3D human skin model, indicated SP gel to be safe for long-term use, without causing irritation, even at high concentrations. In-vitro analysis revealed that SP gel elicited stronger collagen production activities than SP alone, and promoted anti-inflammatory effects with increased skin absorption properties. Moreover, SP gel did not induce melanin synthesis in a keratinocyte-melanocyte co-culture system. Together, the results suggest that SP gel has potential cosmetic effects and applicability as a novel ingredient in anti-aging products.