Aldehyde Dehydrogenase 2 Protects the Kidney from Ischemia-Reperfusion Injury by Suppressing the IκBα/NF-κB/IL-17C Pathway.

Objective: Ischemia-reperfusion injury (IRI) is an important cause of delayed functional recovery after transplantation. This study is aimed at investigating the molecular mechanism of ALDH2 in a kidney ischemia-reperfusion model based on RNA-seq. Methods: We performed kidney ischemia-reperfusion in ALDH2-/- and WT mice and evaluated kidney function and morphology using SCr, HE staining, TUNEL staining, and TEM. We used RNA-seq to compare mRNA expression in ALDH2-/- and WT mice after IR, and then, we verified the related molecular pathways by PCR and western blotting. In addition, activators and inhibitors of ALDH2 were used to alter the activity of ALDH2. Finally, we established a model of hypoxia and reoxygenation in HK-2 cells and clarified the role of ALDH2 in IR by interfering with ALDH2 and using an NF-κB inhibitor. Results: After kidney ischemia-reperfusion, the SCr value increased significantly, kidney tubular epithelial cells were damaged, and the apoptosis rate increased. In the microstructure, mitochondria were swollen and deformed, and ALDH2 deficiency aggravated these changes. The NF-κB pathway and IL-17 pathway were significantly enriched in ALDH2-/- mice compared with WT mice according to KEGG enrichment analysis of the RNA-seq data. The PCR results showed that the mRNA expression levels of IκBα and IL-17B, C, D, E, and F were significantly higher than those in the WT-IR group. Western blot verification results showed that ALHD2 knockdown resulted in increased phosphorylation of IκBα, increased phosphorylation of NF-κB, and increased expression of IL-17C. When we used ALDH2 agonists, the number of lesions and the expression levels of the corresponding proteins were reduced. Knockdown of ALDH2 in HK-2 cells resulted in a higher proportion of apoptotic cells after hypoxia and reoxygenation, but inhibiting the phosphorylation of NF-κB prevented the increase in apoptosis and reduced the protein expression level of IL-17C. Conclusion: ALDH2 deficiency can lead to the aggravation of kidney ischemia-reperfusion injury. RNA-seq analysis and validation by PCR and western blotting revealed that this effect may be due to the promotion of IκBα/NF-κB p65 phosphorylation during ischemia-reperfusion caused by ALDH2 deficiency, which then leads to an increase in inflammatory factors, including IL-17C. Thus, cell death is promoted, and kidney IRI is eventually aggravated. We link ALDH2 deficiency with inflammation, revealing a new idea for ALDH2-related research.

Effect of Matrix Metalloproteinase 23 Accelerating Wound Healing Induced by Hydroxybutyl Chitosan.

Skin wounds may cause severe financial and social burden due to the difficulties in wound healing. Original inert dressings cannot meet multiple needs in the process of wound healing. Therefore, the development of materials to accelerate healing progress is essential and urgent. In the previous study, we found that the homogeneously synthesized hydroxybutyl chitosan (HBCS) had an effective performance in promoting wound healing. Proteomic analysis of the same specimen suggested that matrix metalloproteinase 23 (MMP23) may play a key role in HBCS expediting the progress of wound healing. In this work, we aim to reveal the underlying mechanism of MMP23 in the dynamic process of cutaneous proliferation and repair period. In order to regulate the expression level of MMP23 in the local wound area, we leaded in adeno-associated virus (AAV) to specifically decreased expression quantity of MMP23 in rat skin. In contrast to the negative control groups, we found that the wound closed faster and the collagen fibers and neovascularization were significantly increased in AAV groups. These findings highlighted that MMP23 was involved in wound healing after traumatic injury, and managing the expression of MMP23 could be a potential intervention target to accelerate wound healing.

Antibacterial and antioxidant chitosan nanoparticles improve the preservation effect for donor kidneys in vitro.

Hypothermic machine perfusion (HMP) is a preferable measure to preserve kidneys from donation after cardiac death (DCD), while the current standard perfusate is imperfect. We synthesized amphiphilic chitosan, N-alkylated-O-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (N-alkyl-O-HTCC) as additive in the perfusate, which can self-assembly into micelles in water (size 133 ± 8.48 nm) (ζ-potential 43.9 ± 2.06 mV), with good antibacterial activity for Escherichia coli and Staphylococcus aureus. The derivates can also deliver hydrophobic drug Alda-1 into kidneys through HMP, with drug loading ratio (~42.14%). The delivery system specifically activated mitochondrial acetaldehyde dehydrogenase 2 in kidneys and reduced the ischemic injury. What's more, the addition of N-alkyl-O-HTCC in HMP also activated mitochondria superoxide dismutase 2, presented nice antioxidant activity. These all helped to improve the quality of DCD kidneys. This study provides a feasible amphiphilic carrier for hydrophobic drugs, and provides efficient guidance for perfusate improvement.

Management of immunosuppression in kidney transplant recipients with COVID-19 pneumonia: A summary of 41 confirmed cases reported worldwide.

There is no consensus on immunosuppression management for kidney transplant recipients (KTRs) with SARS-CoV-2 pneumonia. Therefore, we conducted a search in English database from October 2019 to July 2020 and extracted data from cases with treatment details worldwide, and total of 41 recipients with a median age of 50 years were enrolled in this study. Most of them were males (75.8%). The most common presenting symptoms were fever (80.5%), cough (63.4%), and fatigue (41.5%). Patients were classified into three catalogs according to severity of pneumonia: 17 (41.5%) were mild, 15 (36.6%) severe, and 9 (21.9%) critical disease. Laboratory tests revealed that serum creatinine of critical patients was significantly higher than that of mild or severe patients. 68.3% received oxygen support; all patients received antiviral therapy, and 15 (36.6%) recipients were additionally treated with intravenous immunoglobulin and interferon-α. 19.5% of patients maintained immunosuppressive therapy; 36.6% suspended antimetabolite; and 43.9% only treated with corticosteroid. Six (14.6%) patients died (severe: 2, critical: 4); high creatinine with low lymphocyte count was the biggest challenge of immunosuppression management. In all, it is necessary to pay close attention to renal function and lymphocyte count in KTRs infected with COVID-19 and choose appropriate medication programs according to the specific situations.

MMP7 damages the integrity of the renal tubule epithelium by activating MMP2/9 during ischemia-reperfusion injury.

Renal ischemia-reperfusion (IR) injury is a common issue in urological surgery, and the renal tubules, particularly the proximal tubules, are extremely vulnerable to IR injury. In this work, we detected the differently expressed genes (DEGs) between normal rabbit kidneys and IR kidneys by RNA-sequencing, then identified that matrix metalloproteinase-7 (MMP7) played an important role in the progress of IR injury. Indeed, A time-dependent promotion of renal injury was detected in rabbit model, as demonstrated by the increased levels of MMP2/7/9, and the decreased of tight junction protein-1 (TJP1). Furtherly, similar results were confirmed in human renal proximal tubule epithelial (HK-2) cells model. Notably, downregulation of MMP7 affected the activity of MMP2/9 by suppressing expression of cleaved-MMP2/9 not the pro-MMP2/9 protein, which directly alleviated the degradation of TJP1 in HK-2 model. On the contrary, MMP7 had not been affected by inhibiting MMP2/9. In addition, coimmunoprecipitation assay showed that knockdown MMP7 restrained the interaction between MMP2/9 and TJP1. Collectively, this study suggested that MMP7 could serve as early biomarkers for renal tubular injury, and revealed that MMP7 could destroy the integrity of tubular epithelium through degrading TJP1 by activating MMP2/9.

Aldehyde dehydrogenase 2 regulates autophagy via the Akt-mTOR pathway to mitigate renal ischemia-reperfusion injury in hypothermic machine perfusion.

AIMS: Ischemia-reperfusion injury (IRI) is harmful to patients following kidney transplantation. Hypothermic machine perfusion (HMP) can be adopted to preserve grafts and reduce consequential injury. We hypothesized that aldehyde dehydrogenase 2 (ALDH2) partly mitigates kidney IRI via regulating excessive autophagy in HMP. MATERIALS AND METHODS: The rabbits were assigned to 5 groups: Normal, HMP, HMP + Alda-1, HMP + CYA and cold storage (CS). After the rabbit autologous kidney transplantation, renal pathology and function were evaluated by histological analysis, glomerular related proteins (desmin, nephrin), tubular injury factors (NGAL, Ki67), serum creatinine (Cr) and blood urea nitrogen (BUN). Oxidative stress molecular Malondialdehyde (MDA) and superoxide dismutase (SOD2) expression, as well as inflammatory cytokines (TNF-α, IL-6, IL-10) were assessed by immunohistochemistry. The expression of LC3, p62, ALDH2, p-Akt, mTOR, PTEN, p-PTEN, and 4-HNE were measured by immunohistochemistry, RT-PCR, Western blot analysis or ELISA. KEY FINDINGS: HMP was more effective than CS for kidney preservation, with p- ALDH2 expressed in greater quantities in HMP. The results of kidney pathology and function in HMP + Alda-1 were the best. The MDA & SOD2 and the Vyacheslav score were improved in HMP + CYA. ALDH2 reduced 4-HNE-induced oxidative stress, inflammatory infiltration, the expression of LC3, p62 and inhibited autophagy accompanied by activation of p-Akt and mTOR via p-PTEN/PTEN. SIGNIFICANCE: Akt-mTOR autophagy pathway is a novel target for ALDH2 to reduce renal IRI partly by inhibition of 4-HNE in HMP, then protecting the donated kidney received after cardiac death (DCD).

Elucidation of molecular pathways responsible for the accelerated wound healing induced by a novel fibrous chitin dressing.

Fibrous chitin dressing (FCD) prepared from a NaOH-urea aqueous solution of chitin via a physical process was used to study its effect on wound healing using a full-thickness cutaneous wound model in rats and mice. It was demonstrated that wounds in rats covered with the FCD showed faster collagen (especially type I collagen) growth and speedier healing than those with Gauze (12 days versus 16 days). The ability of FCD to promote wound healing was also observed on wild-type (WT) mice. For MyD88-knockout mice, however, FCD displayed no beneficial but an adverse effect on wound healing: the healing time for wounds treated with FCD was even longer than those treated with gauze. Importantly, in vivo studies indicated that FCD-treated mice, compared to gauze-treated ones, exhibited markedly higher expressions of MyD88, IKBα, TGF-ß, P-TßR II, TßR II and P-Smad2/3 in wild-type mice. For MyD88 knockout mice, however, the expressions of those molecules were inhibited and lowered in FCD-treated ones than those treated with gauze. In vitro studies confirmed that chitin increased the expression of TGF-ß, P-TßRII and P-Smad2/3 while the expressions of those molecules were significantly inhibited with CD14 antibody (p < 0.05). These results indicated that FCD accelerated wound healing through a MyD88-dependent pathway, followed by a TGF-ß/Smad pathway. This work not only demonstrated the superior wound healing effect of chitin-derived dressing, but also provided for the first time the underlying molecular mechanism, further establishing chitin as an important biomedical material for potential clinical applications.

Construction of cellulose nanofibers/quaternized chitin/organic rectorite composites and their application as wound dressing materials.

Traumatic injury is a major cause of mortality, and poor wound healing affects millions of people. Thus, the development of effective wound dressings is essential for speeding up wound healing and decreasing mortality. In this study, a suspension of carboxylated brown algae cellulose nanofibers (BACNFs) with a high aspect ratio was freeze dried to prepare a sponge. The sponge showed high porosity and water absorption capacity; thus, it can absorb wound exudates when used as a wound dressing. In addition, quaternized ß-chitin (QC) with antibacterial properties was intercalated into the interlayer space of the organic rectorite (OREC) via electrostatic interactions to obtain composite suspensions (QCRs) with improved antimicrobial activity compared to that of QC alone. Subsequently, the BACNF sponge was soaked in the QCR suspension to absorb QCRs via electrostatic interactions and hydrogen bonding from which cellulose nanofiber/quaternized chitin/organic rectorite composite (BACNF/QCR) sponges were constructed via freeze-drying. The in vivo animal tests demonstrated that the BACNF/QCR sponges rapidly induced hemostasis in a rat tail amputation test, making them superior to the traditional hemostatic materials. Furthermore, BACNFs/QCRs could substantially promote collagen synthesis and neovascularization, thereby accelerating wound healing 3 days earlier than gauze. This multi-functional biomedical material, fabricated using natural substances, shows great potential to be used for wound healing.

Homogeneously Synthesized Hydroxybutyl Chitosans in Alkali/Urea Aqueous Solutions as Potential Wound Dressings.

Wound healing is a clinical challenge, and nontoxic, nonadherent wound dressings that promote healing are urgently needed. Herein, hydroxybutyl chitosans (HBCSs) with the degree of substitution (DS) from 0.41 to 1.38 were synthesized in alkali/urea aqueous solutions, from which sponge-like dressings were prepared by freeze-drying. The pore size of the sponges was in the range of 14.8-18.4 µm, and the porosity was about 98-99%. The compressive strength of the sponges decreased with increasing DS of HBCS. Cytocompatibility studies with normal human dermal fibroblast (NHDF) cells demonstrated that HBCSs were nontoxic and could even promote the growth of fibroblasts. Further tests revealed that HBCS-3 (DS = 0.85) and HBCS-5 (DS = 1.38) exhibited better hemocompatibility and a low blood-clotting index (BCI). Therefore, these two samples were selected as model dressings for in vivo wound-healing assessment in rats. The experiments suggested that HBCS-3 significantly shortened the wound recovery period compared with HBCS-5, chitosan, and gauze by facilitating epithelialization, collagen deposition, and neovascularization and activating the immune system. The results highlighted the potential of HBCSs as efficient dressings for promoting wound healing.

Increased Expression of Aldehyde Dehydrogenase 2 Reduces Renal Cell Apoptosis During Ischemia/Reperfusion Injury After Hypothermic Machine Perfusion.

Hypothermic machine perfusion (MP) can reduce graft's injury after kidney transplantation; however, the mechanism has not been elucidated. In the past decade, many studies showed that aldehyde dehydrogenase 2 (ALDH2) is a protease which can inhibit cell apoptosis. Therefore, this study aims to explore whether ALDH2 takes part in reducing organ damage after MP. Eighteen healthy male New Zealand rabbits (12 weeks old, weight 3.0 ± 0.3 kg) were randomly divided into three groups: normal group, MP group, and cold storage (CS) group (n = 6). The left kidney of rabbits underwent warm ischemia for 35 min through clamping the left renal pedicle and then reperfusion for 1 h. Left kidneys were preserved by MP or CS (4°C for 4 h) in vivo followed by the right nephrectomy and 24-h reperfusion, and then the specimens and blood were collected. Finally, concentration of urine creatinine (Cr), blood urea nitrogen (BUN), and 4-HNE were tested. Renal apoptosis was detected by TUNEL staining, and the expression of ALDH2, cleaved-caspase 3, bcl-2/ bax, MAPK in renal tissue was detected by immunohistochemistry or Western blot; 24 h after surgery, the concentration of Cr in MP group was 355 ± 71µmol/L, in CS group was 511 ± 44 µmol/L (P < 0.05), while the BUN was 15.02 ± 2.34 mmol/L in MP group, 22.64 ± 3.58 mmol/L in CS group (P < 0.05). The rate of apoptosis and expression of cleaved caspase-3, p-P38, p-ERK, and p-JNK in MP group was significantly lower than that in CS group (P < 0.05), while expression of ALDH2 and bcl-2/bax in MP group was significantly higher than that in CS group (P < 0.05); expression of cleaved caspase-3 in both MP and CS group significantly increased as compared with that in normal group (P < 0.05). In conclusion, increased expression of ALDH2 can reduce the renal cell apoptosis through inhibiting MAPK pathway during ischemia/reperfusion injury (IRI) after hypothermic MP.