Substance P preserves pancreatic ß-cells in type 1 and type 2 diabetic mice.

Preservation of pancreatic ß-cells is required for the development of therapies for type 1 and type 2 diabetes (T1D and T2D, respectively). Our previous study demonstrated that substance P (SP) preserves ß-cell populations in mice with streptozotocin-induced T1D. Here, we demonstrated that chronic systemic treatment with SP restored the mass of ß-cells both in nonobese diabetic (NOD) mice with T1D or db/db mice with T2D. SP delayed the onset of T1D in NOD mice via immune modulation. SP inhibited immune infiltration into islets and the salivary glands of NOD mice. In db/db mice, SP treatment rescued glucose intolerance. Moreover, SP inhibited apoptosis, as well as the activation of pancreatic stellate cells in pancreatic islets of db/db mice. SP downregulated the number of α-smooth muscle actin (α-SMA) expressing cells in db/db pancreatic islets. Cleaved-caspase-3 expression was reduced in islets of SP-treated db/db mice compared to that in the control. Therefore, these results suggested that SP may preserve pancreatic ß-cells through immune modulation and protection from the stimulated activation of pancreatic stellate cells and apoptosis in T1D and T2D, respectively.

Substance P preserves pancreatic ß-cells in streptozotocin-induced type 1 diabetic mice.

Preservation of the pancreatic ß-cell population is required for the development of therapies for diabetes, which is caused by a decrease in ß-cells. Here, we demonstrate the antidiabetic effects of substance P (SP) in type 1 diabetes (T1D) mice induced with streptozotocin. SP enhanced the compensatory proliferation of ß-cells in order to restore ß-cells in response to acute injury induced by a single high-dose of streptozotocin. However, SP affected neither the basal proliferation of ß-cells nor their apoptosis. In vitro studies by using the INS-1 pancreatic ß-cell line showed that SP mediated the increase in the proliferation of ß-cells via the activation of Akt. Chronic systemic treatment with SP restored the mass of ß-cells and inhibited insulitis in T1D mice induced with multiple low-doses of streptozotocin. Therefore, systemic treatment with SP may be a promising therapeutic strategy for treating diabetes in patients with loss of functional ß-cells.

Substance P enhances EPC mobilization for accelerated wound healing.

Wound healing is essential for the survival and tissue homeostasis of unicellular and multicellular organisms. The current study demonstrated that the neuropeptide substance P (SP) accelerated the wound healing process, particularly in the skin. Subcutaneous treatment of SP accelerated wound closing, increased the population of α-smooth muscle actin positive myofibroblasts, and increased extracellular matrix deposition at the wound site. Moreover, SP treatment enhances angiogenesis without a local increase in the expression levels of vascular endothelial growth factor and stromal cell-derived factor-1. Importantly, SP treatment increased both the population of circulating endothelial progenitor cells in the peripheral blood and in CD31 positive cells in Matrigel plugs. The tube forming potential of endothelial cells was also enhanced by SP treatment. The results suggested that the subcutaneous injection of SP accelerated the wound healing in the skin via better reconstitution of blood vessels, which possibly followed an increase in the systemic mobilization of endothelial progenitor cells and a more effective assembly of endothelial cells into tubes.

Substance P modulates properties of normal and diabetic dermal fibroblasts.

Dermal fibroblasts play essential roles in wound healing. However, they lose their normal regenerative functions under certain pathologic conditions such as in chronic diabetic wounds. Here, we show that substance P (SP) rescues the malfunctions of dermal fibroblasts in diabetes. SP increased the proliferation of diabetic dermal fibroblasts dose-dependently, although the effect was lower compared to the SP-stimulated proliferation of normal dermal fibroblasts. In contrast to normal dermal fibroblasts, SP increased the expression level of vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1 (SDF-1) in diabetic dermal fibroblast hence, rescuing their angiogenic potential. The cellular characteristics of diabetic dermal fibroblasts modulated by SP would be able to accelerate the wound healing process through faster wound contraction and improved angiogenesis in diabetic chronic wounds. Moreover, SP pretreatment into dermal fibroblasts isolated from diabetic patients would be a promising strategy to develop autologous cell therapy for treating diabetic chronic wounds.