Exploring the Catalytic Flexibility and Reversibility of Plant Glycosyltransferase HtUGT72AS1 for Glycodiversification of Phenolic Compounds.

Plant bioactive metabolites such as flavonoids are usually present in glycosylated forms by the attachment of various sugar groups. In this study, a catalytically flexible and reversible glycosyltransferase (HtUGT72AS1) was cloned and characterized from Helleborus thibetanus. HtUGT72AS1 could directly accept six sugar donors (UDP-glucose/-arabinose/-galactose/-xylose/-N-acetylglucosamine/-rhamnose) to catalyze the 3-OH glycosylation of flavonols. It also catalyzed the 4' and 7-OH glycosylation of other types of flavonoids, which lacked the 3-OH group. Additionally, the HtUGT72AS1-catalyzed reaction was highly reversible when using 2-chloro-4-nitrophenyl glycosides as substrates, which could be used for one-pot or coupled production of bioactive glycosides. It is the first reported UGT for the synthesis of arabinosides and galactosides using a transglycosylation platform. Based on structural modeling and mutagenetic analysis, the mutation of Tyr377 to Ara enhanced the catalytic efficiency of HtUGT72AS1 toward UDP-N-acetylglucosamine, and the V146S mutant gained an improvement in the regioselectivity toward 7-OH of flavonoids.

Epigenetic regulation of macrophage polarization in wound healing.

The immune microenvironment plays a critical role in regulating skin wound healing. Macrophages, the main component of infiltrating inflammatory cells, play a pivotal role in shaping the immune microenvironment in the process of skin wound healing. Macrophages comprise the classic proinflammatory M1 subtype and anti-inflammatory M2 population. In the early inflammatory phase of skin wound closure, M1-like macrophages initiate and amplify the local inflammatory response to disinfect the injured tissue. In the late tissue-repairing phase, M2 macrophages are predominant in wound tissue and limit local inflammation to promote tissue repair. The biological function of macrophages is tightly linked with epigenomic organization. Transcription factors are essential for macrophage polarization. Epigenetic modification of transcription factors determines the heterogeneity of macrophages. In contrast, transcription factors also regulate the expression of epigenetic enzymes. Both transcription factors and epigenetic enzymes form a complex network that regulates the plasticity of macrophages. Here, we describe the latest knowledge concerning the potential epigenetic mechanisms that precisely regulate the biological function of macrophages and their effects on skin wound healing.

Skin γδ T Cells and Their Function in Wound Healing.

For the skin immune system, γδ T cells are important components, which help in defensing against damage and infection of skin. Compared to the conventional αß T cells, γδ T cells have their own differentiation, development and activation characteristics. In adult mice, dendritic epidermal T cells (DETCs), Vγ4 and Vγ6 γδ T cells are the main subsets of skin, the coordination and interaction among them play a crucial role in wound repair. To get a clear overview of γδ T cells, this review synopsizes their derivation, development, colonization and activation, and focuses their function in acute and chronic wound healing, as well as the underlining mechanism. The aim of this paper is to provide cues for the study of human epidermal γδ T cells and the potential treatment for skin rehabilitation.

Consensus on the application of negative pressure wound therapy of diabetic foot wounds.

Because China is becoming an aging society, the incidence of diabetes and diabetic foot have been increasing. Diabetic foot has become one of the main health-related killers due to its high disability and mortality rates. Negative pressure wound therapy (NPWT) is one of the most effective techniques for the treatment of diabetic foot wounds and great progress, both in terms of research and its clinical application, has been made in the last 20 years of its development. However, due to the complex pathogenesis and management of diabetic foot, irregular application of NPWT often leads to complications, such as infection, bleeding and necrosis, that seriously affect its treatment outcomes. In 2020, under the leadership of Burns, Trauma and Tissue Repair Committee of the Cross-Straits Medicine Exchange Association, the writing group for 'Consensus on the application of negative pressure wound therapy of diabetic foot wounds' was established with the participation of scholars from the specialized areas of burns, endocrinology, vascular surgery, orthopedics and wound repair. Drawing on evidence-based practice suggested by the latest clinical research, this consensus proposes the best clinical practice guidelines for the application and prognostic evaluation of NPWT for diabetic foot. The consensus aims to support the formation of standardized treatment schemes that clinicians can refer to when treating cases of diabetic foot.

Keratinocyte growth factor ameliorates mycophenolate mofetil-induced intestinal barrier disruption in mice.

OBJECTIVES: Although mycophenolate mofetil-induced (MMF) effectively improves long-term graft survival, the gastrointestinal (GI) side effects due to MMF-induced GI barrier damage limit its use in clinic. Keratinocyte growth factor (KGF) plays a crucial role in the intestinal protection and repair process. This study is designed to investigate the protective effect of KGF on MMF-induced intestinal mucosal barrier disruption and the potential mechanism. METHODS: Thirty adult male C57BL/6 mice were assigned to one of the following groups: the MMF group, the MMF + KGF group, and the control group (n = 10 in each group). Animals in the MMF group received MMF (500 mg/kg) by gavage once daily for 15 consecutive days; animals in the MMF + KGF group received MMF (500 mg/kg) by gavage and KGF (5 mg/kg) by intraperitoneal injection once daily for 15 consecutive days; and control mice were given an equal volume of vehicle during the 15-day experimental period. In each group, intestinal paracellular permeability, histopathological changes and shifts in tight junction (TJ) protein were evaluated; further, proliferation and apoptosis of intestinal epithelial cells (IECs) were assessed, and intraepithelial lymphocytes (IELs) were isolated and analyzed by flow cytometry. RESULTS: MMF caused intestinal mucosal injury, increased intestinal mucosal permeability, and altered expression of TJ protein. Moreover, MMF treatment inhibited IEC proliferation and increased apoptosis. MMF treatment resulted in a lower proportion of γδ+ T cells in IELs (γδ+ IELs). Conversely, concurrent administration of KGF with MMF effectively alleviated MMF-induced intestinal mucosal disruption, inhibited the increase in intestinal permeability, and maintained TJ protein expression. KGF also reversed the MMF-mediated inhibition of proliferation and promotion of apoptosis in IECs. In addition, KGF significantly enhanced the proportion of γδ+ IELs. CONCLUSION: Our findings suggest that MMF induces intestinal epithelial barrier disruption in mice. KGF may play a protective role to ameliorate the disruption and provide a therapeutic intervention for gastrointestinal disorders induced by MMF.

Vγ4 T Cells Inhibit the Pro-healing Functions of Dendritic Epidermal T Cells to Delay Skin Wound Closure Through IL-17A.

Dendritic epidermal T cells (DETCs) and dermal Vγ4 T cells engage in wound re-epithelialization and skin inflammation. However, it remains unknown whether a functional link between Vγ4 T cell pro-inflammation and DETC pro-healing exists to affect the outcome of skin wound closure. Here, we revealed that Vγ4 T cell-derived IL-17A inhibited IGF-1 production by DETCs to delay skin wound healing. Epidermal IL-1ß and IL-23 were required for Vγ4 T cells to suppress IGF-1 production by DETCs after skin injury. Moreover, we clarified that IL-1ß rather than IL-23 played a more important role in inhibiting IGF-1 production by DETCs in an NF-κB-dependent manner. Together, these findings suggested a mechanistic link between Vγ4 T cell-derived IL-17A, epidermal IL-1ß/IL-23, DETC-derived IGF-1, and wound-healing responses in the skin.

Probing the stereoselectivity of OleD-catalyzed glycosylation of cardiotonic steroids.

The glycosyltransferase OleD variant as a catalyst for the glycosylation of four pairs of epimers of cardiotonic steroids (CTS) are assessed. The results of this study demonstrated that the OleD-catalyze glycosylation of CTS is significantly influenced by the configuration at C-3 and the A/B fusion mode. 3ß-OH and A/B ring cis fusion are favoured by OleD (ASP). An epoxide ring at C-14 and C-15 further increases the bioconversion rate; while an acetyl group at C-16 and lactone ring type at C-17 did not influence the biotransformation. A high conversion rate corresponded to a low K m value. A molecular docking simulation showed that filling of hydrophobic pocket II and interaction with residue Tyr115 may play an important role in the glycosylation reactions catalyzed by OleD glycosyltransferases. Furthermore, the glycosylation products showed a stronger inhibitory activity for Na+, K+-ATPase than the corresponding aglycones. This study provides the first stereoselective properties for OleD (ASP) catalyzed glycosylation.

IL-15 Enhances Activation and IGF-1 Production of Dendritic Epidermal T Cells to Promote Wound Healing in Diabetic Mice.

Altered homeostasis and dysfunction of dendritic epidermal T cells (DETCs) contribute to abnormal diabetic wound healing. IL-15 plays important roles in survival and activation of T lymphocytes. Recently, reduction of epidermal IL-15 has been reported as an important mechanism for abnormal DETC homeostasis in streptozotocin -induced diabetic animals. However, the role of IL-15 in impaired diabetic wound healing remains unknown. Here, we found that, through rescuing the insufficient activation of DETCs, IL-15 increased IGF-1 production by DETCs and thereby promoted diabetic skin wound repair. Regulation of IGF-1 in DETCs by IL-15 was partly dependent on the mTOR pathway. In addition, expression of IL-15 and IGF-1 were positively correlated in wounded epidermis. Together, our data indicated that IL-15 enhanced IGF-1 production by DETCs to promoting diabetic wound repair, suggesting IL-15 as a potential therapeutic agent for managing diabetic wound healing.

Vγ4 γδ T Cells Provide an Early Source of IL-17A and Accelerate Skin Graft Rejection.

Activated γδ T cells have been shown to accelerate allograft rejection. However, the precise role of skin-resident γδ T cells and their subsets-Vγ5 (epidermis), Vγ1, and Vγ4 (dermis)-in skin graft rejection have not been identified. Here, using a male to female skin transplantation model, we demonstrated that Vγ4 T cells, rather than Vγ1 or Vγ5 T cells, accelerated skin graft rejection and that IL-17A was essential for Vγ4 T-cell-mediated skin graft rejection. Moreover, we found that Vγ4 T cells were required for early IL-17A production in the transplanted area, both in skin grafts and in the host epidermis around grafts. Additionally, the chemokine (C-C motif) ligand 20-chemokine receptor 6 pathway was essential for recruitment of Vγ4 T cells to the transplantation area, whereas both IL-1ß and IL-23 induced IL-17A production from infiltrating cells. Lastly, Vγ4 T-cell-derived IL-17A promoted the accumulation of mature dendritic cells in draining lymph nodes to subsequently regulate αß T-cell function after skin graft transplantation. Taken together, our data reveal that Vγ4 T cells accelerate skin graft rejection by providing an early source of IL-17A.

Weakened IL-15 Production and Impaired mTOR Activation Alter Dendritic Epidermal T Cell Homeostasis in Diabetic Mice.

Diabetes is associated with impaired wound healing, which may be caused primarily by a deficiency in dendritic epidermal T cells (DETCs). In the epidermis, IL-15, IGF-1, and mTOR are known to regulate the maintenance of DETCs; however, it is unclear how these molecules may intersect to regulate DETC homeostasis in diabetes. Here, we show that the reduction of DETCs in the epidermis of diabetic mice is caused by altered homeostasis mediated by a reduction in IL-15 levels. Both impaired mTOR activation and reduction of IL-15 in the epidermis play important roles in DETC homeostasis. Moreover, IGF-1 drives keratinocytes to produce IL-15. The activation of IL-15 is dependent on mTOR, and conversely, mTOR regulates IGF-1 production in DETC, in a classic feedback regulatory loop. Our data suggest that in the setting of diabetes, reduced IGF-1, impaired mTOR pathway activation and reduced IL-15 in the epidermis function coordinately to promote altered DETC homeostasis and delayed skin wound closure.

The progress of Chinese burn medicine from the Third Military Medical University-in memory of its pioneer, Professor Li Ao.

Professor Li Ao was one of the founders of Chinese burn medicine and one of the most renowned doctors and researchers of burns in China. He established one of the Chinese earliest special departments for burns at Third Military Medical University (TMMU) in 1958. To memorialize Professor Li Ao on his 100th birthday in 2017 and introduce our extensive experience, it is our honor to briefly review the development and achievement of the Chinese burn medicine from TMMU. The epidemiology and outcomes of admitted burn patients since 1958 were reviewed. Furthermore, main achievements of basic and clinical research for the past roughly 60 years were presented. These achievements mainly included the Chinese Rule of Nine, fluid resuscitation protocol, experience in inhalation injury, wound treatment strategies, prevention and treatment of burn infections, nutrition therapy, organ support therapies, and rehabilitation. The progress shaped and enriched modern Chinese burn medicine and promoted the development of world burn medicine.

Defects in dermal Vγ4 γ δ T cells result in delayed wound healing in diabetic mice.

The skin serves as a physical and chemical barrier to provide an initial line of defense against environmental threats; however, this function is impaired in diabetes. Vγ4 γ δ T cells in the dermis are an important part of the resident cutaneous immunosurveillance program, but these cells have yet to be explored in the context of diabetes. In this study, we observed that the impaired maintenance of dermal Vγ4 γ δ T cells is caused by reduced production of IL-7 in the skin of diabetic mice, which was closely associated with weakened activation of the mTOR pathway in the epidermis of diabetic mice. Weakened CCL20/CCR6 chemokine signaling resulted in the impaired recruitment of dermal Vγ4 γ δ T cells following wounding in diabetic mice. Meanwhile, reduced levels of IL-23 and IL-1ß in the dermis around the wounds of diabetic mice resulted in the impaired production of IL-17 by dermal Vγ4 γ δ T cells. Therefore, diminished dermal Vγ4 γ δ T cells and impaired IL-17 production by these cells were important factors in the markedly reduced IL-17 levels in the skin around the wounds of diabetic mice. Because reduced IL-17 levels at the wound edge have been closely associated with delayed wound closure in diabetic mice, defects in dermal Vγ4 γ δ T cells may be an important mechanism underlying delayed wound healing in diabetic mice.

Novel stereoselective bufadienolides reveal new insights into the requirements for Na(+), K(+)-ATPase inhibition by cardiotonic steroids.

Cardiotonic steroids (CTS) are clinically important drugs for the treatment of heart failure owing to their potent inhibition of cardiac Na(+), K(+)-ATPase (NKA). Bufadienolides constitute one of the two major classes of CTS, but little is known about how they interact with NKA. We report a remarkable stereoselectivity of NKA inhibition by native 3ß-hydroxy bufalin over the 3α-isomer, yet replacing the 3ß-hydroxy group with larger polar groups in the same configuration enhances inhibitory potency. Binding of the two (13)C-labelled glycosyl diastereomers to NKA were studied by solid-state NMR (SSNMR), which revealed interactions of the glucose group of the 3ß- derivative with the inhibitory site, but much weaker interactions of the 3α- derivative with the enzyme. Molecular docking simulations suggest that the polar 3ß-groups are closer to the hydrophilic amino acid residues in the entrance of the ligand-binding pocket than those with α-configuration. These first insights into the stereoselective inhibition of NKA by bufadienolides highlight the important role of the hydrophilic moieties at C3 for binding, and may explain why only 3ß-hydroxylated bufadienolides are present as a toxic chemical defence in toad venom.

Dendritic epidermal T cells facilitate wound healing in diabetic mice.

The impairment of skin repair in diabetic patients can lead to increased morbidity and mortality. Proper proliferation, apoptosis and migration in keratinocytes are vital for skin repair, but in diabetic patients, hyperglycemia impairs this process. Dendritic epidermal T cells (DETCs) are an important part of the resident cutaneous immunosurveillance program. We observed a reduction in the number of DETCs in a streptozotocin-induced diabetic mouse model. This reduction in DETCs resulted in decreased IGF-1 and KGF production in the epidermis, which is closely associated with diabetic delayed wound closure. DETCs ameliorated the poor wound-healing conditions in diabetic mice by increasing keratinocyte migration and proliferation and decreasing keratinocyte apoptosis in diabetes-like microenvironments. Our results elucidate a new mechanism for diabetic delayed wound closure and point to a new strategy for the treatment of wounds in diabetic patients.

SDF-1/CXCR4 Axis Promotes MSCs to Repair Liver Injury Partially through Trans-Differentiation and Fusion with Hepatocytes.

MSCs have become a popular target for developing end-stage liver therapies. In this study, two models of bone marrow chimeric mice were used to construct the liver failure models. Then it was found that MSCs can transdifferentiate into hepatocyte-like cells and these hepatocyte-like cells can significantly express albumin. Furthermore it was also found that MSCs can fuse with the hepatocytes and these cells had the proliferation activity. However, the percentage of transdifferentiation was significantly higher than fusion. So it was considered that MSCs which transdifferentiated into hepatocyte-likes cells played important roles for repairing the injuring liver function.

miR-27b represses migration of mouse MSCs to burned margins and prolongs wound repair through silencing SDF-1a.

BACKGROUND: Interactions between stromal cell-derived factor-1α (SDF-1α) and its cognate receptor CXCR4 are crucial for the recruitment of mesenchymal stem cells (MSCs) from bone marrow (BM) reservoirs to damaged tissues for repair during alarm situations. MicroRNAs are differentially expressed in stem cell niches, suggesting a specialized role in stem cell regulation. Here, we gain insight into the molecular mechanisms involved in regulating SDF-1α. METHODS: MSCs from green fluorescent protein transgenic male mice were transfused to irradiated recipient female C57BL/6 mice, and skin burn model of bone marrow-chimeric mice were constructed. Six miRNAs with differential expression in burned murine skin tissue compared to normal skin tissue were identified using microarrays and bioinformatics. The expression of miR-27b and SDF-1α was examined in burned murine skin tissue using quantitative real-time PCR (qPCR) and immunohistochemistry (IHC), enzyme-linked immunosorbent assay (ELISA). The Correlation of miR-27b and SDF-1α expression was analyzed by Pearson analysis Correlation. miRNAs suppressed SDF-1α protein expression by binding directly to its 3'UTR using western blot and luciferase reporter assay. The importance of miRNAs in MSCs chemotaxis was further estimated by decreasing SDF-1α in vivo and in vitro. RESULTS: miR-23a, miR-27a and miR-27b expression was significantly lower in the burned skin than in the normal skin (p<0.05). We also found that several miRNAs suppressed SDF-1α protein expression, while just miR-27a and miR-27b directly bound to the SDF-1α 3'UTR. Moreover, the forced over-expression of miR-27a and miR-27b significantly reduced the directional migration of mMSCs in vitro. However, only miR-27b in burn wound margins significantly inhibited the mobilization of MSCs to the epidermis. CONCLUSION: miR-27b may be a unique signature of the stem cell niche in burned mouse skin and can suppress the directional migration of mMSCs by targeting SDF-1α by binding directly to its 3'UTR.

Effects of glycyl-glutamine dipeptide supplementation on myocardial damage and cardiac function in rats after severe burn injury.

Glutamine decreases myocardial damage in ischemia/reperfusion injury. However, the cardioprotective effect of glutamine after burn injury remains unclear. Present study was to explore the protective effect of glycyl-glutamine dipeptide on myocardial damage in severe burn rats. Seventy-two Wistar rats were randomly divided into three groups: normal control (C), burned control (B) and glycyl-glutamine dipeptide-treated (GG) groups. B and GG groups were inflicted with 30% total body surface area of full thickness burn. The GG group was given 1.5 g/kg glycyl-glutamine dipeptide per day and the B group was given the same dose of alanine via intraperitoneal injection for 3 days. The serum CK, LDH, AST, and, blood lactic acid levels, as well as the myocardium ATP and GSH contents, were measured. The indices of cardiac contractile function and histopathological change were analyzed at 12, 24, 48, and 72 post-burn hours (PBH). The serum CK, LDH, AST and blood lactic acid levels increased, and the myocardium ATP and GSH content decreased in both burned groups. Compared with B group, the CK, LDH, AST and blood lactic acid levels reduced, myocardium ATP and GSH content increased in GG group. Moreover, the inhibition of cardiac contractile function and myocardial histopathological damage were reduced significantly in GG group. We conclude that myocardial histological structure and function were damaged significantly after burn injury, glycyl-glutamine dipeptide supplementation is beneficial to myocardial preservation by improving cardiocyte energy metabolism, increasing ATP and glutathione synthesis.

CXCL12/CXCR4 axis promotes mesenchymal stem cell mobilization to burn wounds and contributes to wound repair.

BACKGROUND: Bone marrow-derived mesenchymal stem cells (BM-MSCs) play a crucial role in tissue repair. Their role in thermal burn wound regeneration and the relevant mechanism, however, is rarely studied. METHODS: BM-MSCs from green fluorescent protein transgenic male mice were transfused to irradiated recipient female C57BL/6 mice. Twenty-one days later, the female mice were inflicted with burn wounds. The size of the burned area was measured by an in vivo fluorescence imaging system, and BM-MSC chemotaxis and epithelialization were estimated by fluorescence in situ hybridization and immunofluorescence technology. The expression of CXCL12 and CXCR4 in the wound margin was detected by enzyme-linked immunosorbent assay and immunohistochemistry. The importance of CXCL12/CXCR4 signaling in BM-MSC chemotaxis was further estimated by blocking CXCR4 in vivo and in vitro. RESULTS: In vivo imaging results showed that BM-MSCs migrated to the injured margins. Fluorescence in situ hybridization and immunofluorescence technology revealed that Y chromosome-positive cells derived from green fluorescent protein transgenic mice were detected to be colocalized with keratin protein. Enzyme-linked immunosorbent assay revealed increased levels of CXCL12 and CXCR4 protein in the wound sites of BM-MSC-treated chimeric mice after burn. Immunohistochemistry also disclosed that CXCL12 levels were elevated at postburn day 7 compared with day 0. Furthermore, pretreatment of the BM-MSCs with the CXCR4 antagonist AMD3100 significantly inhibited the mobilization of BM-MSCs in vitro and in vivo, which attenuated wound closure. CONCLUSION: BM-MSC migration to the burned margins promotes the epithelialization of the wound, and mobilization of BM-MSCs is mediated by CXCL12/CXCR4 signaling.

A survey on the current status of burn rehabilitation services in China.

BACKGROUND: In China, there is a very long history of burn wound treatment, but the specialised burn care units were set up only from 1958. With more than 50 years of practice, great achievements have been made in burn wound care and operations in the country. However, in terms of burn rehabilitation, the development appears to be slow. In order to determine the current status of burn rehabilitation services in China, a survey was conducted to various burn centres in China. METHODS: A comprehensive survey was conducted as well as to collect data related to (1) the admissions and staffing of the burn centres; (2) availability of rehabilitation services, number and educational background of specialised personnel dedicated in burn rehabilitation therapy; and (3) the difficulties leading to the lag of the burn rehabilitation services. The survey was sent to the chiefs of 87 burn centres via e-mail and they were requested to fill out the survey questionnaire and to send it back. For those who did not respond within 1 month, a reminder was sent. RESULTS: There are totally 39 (44.8%) burn centres responding to our survey. These centres were geographically distributed in nearly 70% of the administrative provinces in China; hence, the results could well represent the current burn care system. Most centres have recognised the importance of rehabilitation therapy and remarkable improvements of outcome in burn patients have been achieved. There are a very huge number of burn patients that need rehabilitation therapy, but most centres face the problems of shortage of rehabilitation therapists, which apparently could lead to the difficulties in delivering a quality rehabilitation programme for patients. Although the time of rehabilitation therapy is instituted far earlier than before, it is still not widely accepted in the acute burn care stage. There are more specialists joining the burn centre and becoming members of the professional burn team. However, professional education and training in the burn specialty appear to be sparse. There is room for improvement. Problems that impede the progress of rehabilitation therapy are: lack of rehabilitation knowledge in medical staff as well as the public, the shortage of specialised personnel and relatively low educational background of this team, lack of standard guidelines for rehabilitation treatment instructions and lack of funding from the government. CONCLUSION: After 20 years of clinical practice, rehabilitation concepts are well accepted and many forms of rehabilitation techniques are carried out in most burn centres that responded to the survey. Yet, the results also indicate that there is a short history of rehabilitation practice among the burn centres. There is a burning need to enhance the development of rehabilitation services so as to meet the demands of management of severely burned patients in China. Some suggestions are made to improve the current burn rehabilitation services which would include: (1) provide rehabilitation education programmes for burn surgeons, therapists, nurses, as well as patients, families and the public; (2) set up standard guidelines for clinical instruction of rehabilitation therapy; (3) build an interdisciplinary burn team; (4) more investigation and research on the physical and psychological outcomes of burn patients; and (5) implement administrative measures in terms of staffing, funding and offering insurance to burn survivors.