Metformin accelerates bone fracture healing by promoting type H vessel formation through inhibition of YAP1/TAZ expression

Due to increasing morbidity worldwide,fractures are becoming an emerging public health concern.This study aimed to investigate the effect of metformin on the healing of osteoporotic as well as normal fractures.Type H vessels have recently been identified as a bone-specific vascular subtype that supports osteogenesis.Here,we show that metformin accelerated fracture healing in both osteoporotic and normal mice.Moreover,metformin promoted angiogenesis in vitro under hypoxia as well as type H vessel formation throughout fracture healing.Mechanistically,metformin increased the expression of HIF-1α,an important positive regulator of type H vessel formation,by inhibiting the expression of YAP1/TAZ in calluses and hypoxia-cultured human microvascular endothelial cells(HMECs).The results of HIF-1αor YAP1/TAZ interference in hypoxia-cultured HMECs using si RNA further suggested that the enhancement of HIF-1αand its target genes by metformin is primarily through YAP1/TAZ inhibition.Finally,overexpression of YAP1/TAZ partially counteracted the effect of metformin in promoting type H vessel-induced angiogenesis-osteogenesis coupling during fracture repair.In summary,our findings suggest that metformin has the potential to be a therapeutic agent for fractures by promoting type H vessel formation through YAP1/TAZ inhibition.

Inhibition of LOX-1 alleviates the proinflammatory effects of high-mobility group box 1 in Aspergillus fumigatus keratitis

AIM: To investigate the inflammatory amplification effect of high-mobility group box 1(HMGB1) in Aspergillus fumigatus(A. fumigatus) keratitis and the relationship between lectin-like oxidized low-density lipoprotein receptor 1(LOX-1) and HMGB1 in keratitis immune responses.METHODS: Phosphate buffer saline(PBS), and Boxb were injected into BALB/c mice subconjunctivally before the corneas were infected with A. fumigatus. RAW264.7 macrophages and neutrophils were pretreated with PBS and Boxb to determine the HMGB1 inflammatory amplification effects. Abdominal cavity extracted macrophages were pretreated with Boxb and Poly(I)(a LOX-1 inhibitor) before A. fumigatus hyphae stimulation to prove the the relationship between the two molecules. LOX-1, interleukin-1β(IL-1β), tumor necrosis factor-α(TNF-α), macrophage inflammatory protein-2(MIP-2) and IL-10 were assessed by polymerase chain reaction and Western blot.RESULTS: Pretreatment with Boxb exacerbated corneal inflammation. In macrophages and neutrophils, A. fumigatus induced LOX-1, IL-1β, TNF-α and MIP-2 expression in Boxb group was higher than those in PBS group. Poly(I) treatments before infection alleviated the proinflammatory effects of Boxb in abdominal cavity extracted macrophages. Pretreatment with Boxb did not influence Dectin-1 mRNA levels in macrophages and neutrophils.CONCLUSION: In fungal keratitis, HMGB1 is a proinflammatory factor in the first line of immune response. HMGB1 mainly stimulates neutrophils and macrophages to produce inflammatory cytokines and chemokines during the immune response. LOX-1 participates in HMGB1 induced inflammatory exacerbation in A. fumigatus keratitis.

Regulation of LOX-1 on adhesion molecules and neutrophil infiltration in mouse Aspergillus fumigatus keratitis

AIM:To determine whether lectin-like ox-LDL receptor(LOX-1)regulates adhesion molecules expression and neutrophil infiltration in Aspergillus fumigatus(A.fumigatus)keratitis of C57 BL/6 mice.METHODS:C57 BL/6 mice were pretreated with a neutralizing antibody to LOX-1(5μg/5μL)or control nonspecific IgG(5μg/5μL),LOX-1 inhibitor Poly-I(2μg/5μL)or PBS by subconjunctival injection.Fungal keratitis(FK)mouse models of C57 BL/6 mice were established by scraping corneal central epithelium,smearing A.fumigatus on the corneal surface and covering the eye with contact lenses.The corneal response to infection was assessed via clinical score.The mRNA levels of the adhesion molecules intercellular cell adhesion molecule-1(ICAM-1),vascular cell adhesion molecule-1(VCAM-1),P-selectin and E-selectin were tested in control and infected corneas by reverse transcriptionpolymerase chain reaction(RT-PCR).The protein levels of ICAM-1 were evaluated by immunofluorescence(IF)and Western blot.Neutrophils were extracted from the abdominal cavity of C57 BL/6 mice followed by pretreatment using antibody to LOX-1(10μg/mL)or control nonspecific IgG(10μg/mL),the Poly-I(4μg/mL)or PBS.The cells were then stimulated with A.fumigatus and tested mRNA and protein levels of lymphocyte function-associated antigen-1(LFA-1)using RT-PCR and Western blot.IF and myeloperoxidase(MPO)assays were used to assess neutrophil infiltration in mice corneas.RESULTS:Pretreatment of LOX-1 antibody or the Poly-I reduced the degree of inflammation of cornea and decreased the clinical FK score compared with pretreatment of IgG or PBS(both P<0.01).And these pretreatment also displayed an obvious decline in the mRNA levels of ICAM-1,VCAM-1,P-selectin,E-selectin and LFA-1 expression compared with control groups(all P<0.01).Furthermore,pretreated with LOX-1 antibody or Poly-I,the protein levels of ICAM-1 and LFA-1 also decreased compared with control groups(all P<0.05).Neutrophil infiltration in the cornea was significantly reduced after pretreatment of LOX-1 antibody or Poly-I compared with control groups by IF and MPO assays(both P<0.01).CONCLUSION:Inhibition of LOX-1 can decrease the expression of adhesion molecules and reduce neutrophil infiltration in A.fumigatus infected corneas of C57 BL/6 mice.

Role of the IL-33/ST2/p38 signaling pathway in the immune response of corneal epithelial cells to Aspergillus fumigatus infection

AIM: To investigate the expression of interleukin(IL)-33 in the cornea and human corneal epithelial cells(HCECs) exposed to Aspergillus fumigatus(A. fumigatus), and to determine the function of IL-33/ST2/p38 signaling pathway in the immune response of corneal epithelial cells to A. fumigatus infection.METHODS: The mRNA and protein expression of IL-33 in HCECs and mice corneas were examined by quantitative real-time reverse transcription polymerase chain reaction(q RT-PCR) and Western blot analysis, respectively. IL-33 expression was also detected in cornea samples from healthy donors and patients with fungal keratitis with immunohistochemistry. The cultured HCECs were treated with inactive A. fumigatus hyphae at various concentrations with or without recombinant human IL-33 protein, soluble recombinant ST2 protein, specific ST2 neutralizing antibody, or the mitogen-activated protein kinase(MAPK) p38 inhibitor SB203580 for evaluation of the expression and activation of IL-33/ST2/p38 signaling in the regulation of proinflammatory cytokines. The production levels of IL-6 and IL-1β were determined by qR T-PCR and enzymelinked immunosorbent assay(ELISA). The proliferation of HCECs was determined by a Cell Counting Kit-8(CCK8) assay and cell count.RESULTS: IL-33 expression levels increased in the corneal tissues of patients with fungal keratitis and in mice corneas of experimental A. fumigatus infection,as well as in HCECs with infection of A. fumigatus. A. fumigatus strongly stimulated HCECs-generated proinflammatory cytokine(IL-6 and IL-1β) production at both the mRNA and protein levels. This production of proinflammatory mediators stimulated by A. fumigatus was further stimulated by IL-33 and was prevented by soluble ST2 protein or ST2 neutralizing antibody. Moreover, IL-33 naturally promoted the p38 phosphorylation induced by A. fumigatus, which was suppressed by soluble ST2 protein. The MAPK p38 inhibitor SB203580 also inhibited the A. fumigatus-induced proinflammatory cytokine production. IL-33 administration for 48 h and 72 h promoted the proliferation of HCECs, which was attenuated by treatment with soluble recombinant human ST2 protein.CONCLUSION: A. fumigatus elevates IL-33 expression in human and mice corneas and HCECs. Thus, IL-33/ST2/p38 signaling may play an important role in amplifying the immune response of corneal epithelial cells to A. fumigatus infection. Besides, IL-33 promotes the cell proliferation of HCECs via its receptor ST2. These findings suggest a novel autocrine mechanism of amplification of the fungalinduced inflammatory response in the corneal epithelium, highlighting a potential therapeutic target for fungal keratitis.

Expression and role of aryl hydrocarbon receptor in Aspergillus fumigatus keratitis

●AIM:To observe the expression and role of aryl hydrocarbon receptor(Ah R)in the immune response of mouse cornea infected with Aspergillus fumigatus(A.fumigatus).●METHODS:Murine models of A.fumigatus keratitis were established by scraping the central epithelium of mouse cornea,daubing A.fumigatus on the cornea and covering with a contact lens.The mice were randomly divided into the control group and the A.fumigatus-infected(A.F.)group for 1,3 and 5 d respectively,which corneas were daily monitored by a slit lamp microscope and the clinical scores were also recorded timely after infection.In this study,immunofluorescence staining was used to detect the expression and localization of Ah R in mouse corneas,and the m RNA and protein of Ah R were detected by reverse transcription-polymerase chain reaction(RT-PCR)and Western blot.In addition,mouse peritoneal macrophages were stimulated by A.fumigatus with or without the pretreatment of Ah R antagonist CH223191 and Ah R agonist FICZ,and the tumor necrosis factor alpha(TNF-α),inducible nitric oxide synthase(i NOS),interleukin-10(IL-10)and Arg-1 m RNA were detected by RT-PCR.●RESULTS:According to the results of the slit light photography,it was clearly indicated that the corneal inflammation were the most severe and the clinical score became the highest as well on the 3 rd day after the infection of A.fumigatus.Contrasted with the control group,the expression of Ah R in the corneal epithelial cells infected with A.fumigatus was significantly increased detected by immunofluorescence staining.Ah R mainly expressed in the nucleus and cytoplasm of corneal epithelial cells.Consistent with the transcriptional level of Ah R m RNA,the expression level of Ah R protein reached the peak on the 3 rd day after infection which was detected by Western blot.Furthermore,RT-PCR showed that CH223191 up-regulated the expression of TNF-αand i NOS and down-regulated the expression of IL-10 and Arg-1 in peritoneal macrophages;inversely,FICZ reduced the expression of TNF-αand i NOS while elevated the expression of IL-10 and Arg-1.●CONCLUSION:Ah R is involved in the pathogenesis of A.fumigatus keratitis and induced immune protection in anti-A.fumigatus immune response by inhibiting M1 and increasing M2 phenotype macrophage-related inflammatory factors.

Changes in corneal innervation and pain responses in fungal keratitis

AIM: To characterize changes in the cornea nerve and pain responses in fungal keratitis(FK).METHODS: A retrospective analysis of in vivo confocal microscopy images of 11 FK corneas was performed, and the results were compared with those for 11 normal corneas. Subbasal corneal nerves were analyzed for total nerve number, main nerve trunk number, branching patterns and tortuosity. C57 BL/6 mice were infected with Aspergillus fumigatus. Disease severity was determined through clinical scoring and slit lamp photography. Corneas were harvested at 1, 3, 5, and 7 d post infection(p.i.) and assessed for β III tubulin. Corneal mechanical sensitivity thresholds were detected by von Frey test. β-endorphin(β-EP) and μ receptor protein expression was detected through Western blotting.RESULTS: Total nerve number, main nerve trunk number, and nerve branching were significantly lower in FK patients than in controls, but tortuosity was not significantly different. In infected mice, subbasal nerve density decreased from 1 d p.i., reaching a minimum at 5 d p.i. Clinical scores rose at 1 d p.i., peaked at 3 d p.i., and decreased at 5 d p.i. Mechanical sensitivity thresholds showed the same trends. β-EP and μ receptor protein expression increased after infection.CONCLUSION: Corneal nerve density is lower in FK patients and Aspergillus fumigatus-infected mice than in controls. Pain sensitivity decreases with postinfection corneal ulcer aggravation. β-EP and μ receptor proteins are both upregulated in infected mouse corneas.

Regulation of lipoxygenase-1 and Dectin-1 on interleukin-10 in mouse Aspergillus fumigatus keratitis

AIM： To investigate the regulation of lipoxygenase （LOX）-1 and Dectin-1 on interleukin-10 （IL-10） production in mice with Aspergillus fumigatus （A. fumigatus） keratitis. METHODS： The corneas of C57BL/6 mice were pretreated with LOX-1 inhibitor Poly（I） or Dectin-1 siRNA separately before the infection of A. fumigatus. Polymerase chain reaction （PCR） and Western blot were used to detect the expression of IL-10. RESULTS： The mRNA and protein expressions of IL-10 were significantly increased in mice with A. fumigatus keratitis. Compared with the group pretreated with sterile water before infection, Poly（I） pretreatment suppressed IL-10 expression significantly. Compared with the group pretreated with scrambled siRNA before infection, Dectin-1 siRNA pretreatment significantly reduced IL-10 expression in response to A. fumigatus infection. CONCLUSION： LOX-1 and Dectin-1 regulate IL-10 production in mouse A. fumigatus keratitis.

Mincle in the innate immune response of mice fungal keratitis

AIM： To investigate how macrophage inducible C-type lectin（Mincle） influences inflammation in mice fungal keratitis induced by Aspergillus fumigatus（A. fumigatus）.METHODS： C57 BL/6 mice were infected with A. fumigatus after pretreated with Mincle agonist TDB or Mincle neutralizing antibody（MincleAb）, taking DMSO or IgG as control group respectively. The cornea lesions were monitored with slit-lamp microscope and evaluated by clinical score. Mincle expression was assessed using reverse transcriptionploymerase chain reaction（RT-PCR） and immunostaining. The expression of cytokines（IL-1β, TNF-α and IL-6） chemokines（CXCL-1 and MIP-2） was determined by RTPCR and ELISA. Neutrophil infiltration was observed by immunostaining. The levels of nitric oxide（NO） generated by corneas were tested by Griess reaction. RESULTS： Mincle mRNA and protein levels were higher in infected corneas than normal corneas of C57 BL/6 mice, saving clinical scores revealed differences. When pretreated with Mincle agonist TDB, the mRNA and protein levels of IL-1β, TNF-α and IL-6 in infected corneas were significantly increased compared with the control group（P〈0.01）. Results of the counterpart in corneas pretreated with Mincle neutralizing antibody was decreased consistently（P〈0.01）. Expression of CXCL1 and MIP-2 mRNA levels were upregulated in TDB group and down-regulated in Mincle Ab group（P〈0.01）, coincide with neutrophil aggregation degree in corneas showed by immunostaining. As for the concentration of NO, it was promoted in TDB group compared with DMSO control group, and decreased in Mincle Ab group compared with Ig G control group.CONCLUSION： Mincle plays a dual role in mice fungal keratitis. It participates in the innate immune system by enhancing inflammation. What＇s more, Mincle can mediate cytotoxic effects by regulating the formation of NO.

Disparate expression of autophagy in corneas of C57BL/6 mice and BALB/c mice after Aspergillus fumigatus infection

AIM: To determine the disparate expression of autophagy in the Aspergillus fumigatus(A. fumigatus) keratitis between susceptible C57 BL/6 mice and resistant BALB/c mice.METHODS: C57 BL/6 and BALB/c mice were used to establish fungal keratitis models. Disease severity and inflammatory response were observed by slit lamp microscopy in A. fumigatus-infected corneas of C57 BL/6 and BALB/c mice at 1, 3 and 5 d. Hematoxylin-eosin(H&E) staining was used to detect pathological changes of corneas. The expression of autophagy-related proteins Beclin-1, LC3, SQSTM1/p62, and LAMP-1 was assessed by Western blot in C57 BL/6 and BALB/c mice at 1, 3 and 5 d post infection(p.i.). Immunofluorescent staining was used to test the expression of LC3 in corneas after A. fumigatus infection.RESULTS: Keratitis severity was higher in C57 BL/6 mice versus BALB/c mice at 1, 3 and 5 d p.i. H&E staining showed that the number of inflammatory cells was larger and the severity of ulcer was higher in C57 BL/6 mice than in BALB/c mice after stimulation with A. fumigatus. Higher expression of LAMP-1, Beclin-1, and LC3 was shown in C57 BL/6 mice corneas than in BALB/c mice corneas at 1, 3 and 5 d p.i., while the expression of p62 was lower in C57 BL/6 mice. The fluorescence of LC3 was significantly increased in corneas of C57 BL/6 mice compared with BALB/c mice after A. fumigatus infection.CONCLUSION: The expression of autophagy is higher in corneas of C57 BL/6 mice than in BALB/c mice afterA. fumigatus infection. Autophagy may be positively correlated with keratitis severity and pathological changes.

Parasitic relationship of Cistanche deserticola and host-plant Haloxylon ammodendron based on genetic variation of host

Objective: Cistanche deserticola is a famous and endangered medicinal plant that is parasitic upon Haloxylon ammodendron with rather low parasitic rates. It is important to find high affinity germplasms for increasing the survival of C. deserticola. However, little is known in genetic variation and high affinity populations of H. ammodendron in China.Methods: In this study, 98 accessions of H. ammodendron seeds were collected from five regions covering almost the entire natural distribution of H. ammodendron in China. Their genetic variations were analyzed using AFLP and ITS by the maximum parsimony method, and a dendrogram was constructed using the unweighted pair-group method with arithmetic average(UPGMA). The parasitic rates of C. deserticola on different accessions of H. ammodendron were calculated in the field experiment.Results: Both AFLP and ITS methods consistently revealed that there was a high level of genetic diversity in the natural populations of H. ammodendron. Hierarchical population structure analysis uncovered a clear pattern that all populations were grouped into three main clusters, and eight populations from eastern region were genetically clustered together. These regions were significantly differentiated(P < 0.05), 13.10% of variation occurred among populations, and 86.90% within populations was revealed by analysis of molecular variance(AMOVA). The populations of Inner Mongolia had the highest parasitic rates followed by Ganjiahu Reserve and Yongning Plantation for the top three, which were not completely related to the genetic variation.Conclusion: Genetic characteristics of H. ammodendron in China were clarified and the order of affinity of different populations was given, which were primers for discovering high affinity germplasms.