CX3 chemokine receptor 1 deficiency leads to reduced dendritic complexity and delayed maturation of newborn neurons in the adult mouse hippocampus

Previous studies have shown that microglia impact the proliferation and differentiation of neu- rons during hippocampal neurogenesis via the fractalkine/CX3 chemokine receptor i （CX3CRI） signaling pathway. However, whether microglia can influence the maturation and dendritic growth of newborn neurons during hippocampal neurogenesis remains unclear. In the present study, we found that the number of doublecortin-positive cells in the hippocampus was decreased, and the dendritic length and number of intersections in newborn neurons in the hippocampus were reduced in transgenic adult mice with CX3CR1 deficiency （CX3CRl^GFP/GFe）. Furthermore, after experimental seizures were induced with kainic acid in these CX3CRl-deficient mice, the expression of c-fos, a marker of neuronal activity, was reduced compared with wild-type mice. Collectively, the experimental findings indicate that the functional maturation of newborn neu- rons during hippocampal neurogenesis in adult mice is delayed by CX3CR1 deficiency.

Expression and purification of recombinant human chemokine SDF-1β in E. coli

Objective: To obtain recombinant human SDF-1β expressed in E. colt and purify SDF-lfi with bio-logical activity from the bacterium. Methods: A thioredoxin-SDF-1β fusion protein (26×103) composed of230 amino acid residues was expressed in E. coli AD494 (DE3)pLysS under the induction of IPTG whenpET32a( + )-SDF-1β was used as an expression vector. Purified SDF-lfi was produced through following pro-cedures: Bacteria lysis, metal-chelated affinity chromatography (MAC), enterokinase digestion to separateSDF-lfi from fusion protein, cation exchange chromatography (CEC) and reverse-phase high performance liq-uid chromatography (RP-HPLC). Western blot with anti-SDF-1β monoclonal antibody (mAb), N-terminalamino acid sequencing, ligand-binding assay and cytosensor/microphysiometry were used to investigate thebiochemical characters and biological activities of the purified SDF-1β. Results: From 10% to 15% of totalbacterium protein was expressed as fusion protein. Approximately 400 fig purified SDF-1β (7. 8×103) con-sisting of 71 amino acid residues were produced from 1 L of fermented bacteria. Western blot showed that an-ti-SDF-1β mAb bound with the purified SDF-1β specifically. N-terminal amino acid sequencing indicates thatN-terminus of purified SDF-1β possessed as the same amino acid sequence as nature one. Purified SDF-1β notonly had the binding activity with CXCR4 expressing cells [Kd= (12. 20±2. 99) mnol/L], but also activatedCXCR4 expressing cell signaling specifically in a dose-dependence manner. Conclusion: The purified recombi-nant human SDF-1β produced with this method possesses biochemical characters and biological activities assame as those nature human SDF-1β.

CXCR4 antagonist AMD3100 attenuates colonic damage in mice with experimental colitis

AIM:To investigate the effects of the chemokine stromal cell-derived factor-1(CXCL12) receptor(CXCR4) antagonist AMD3100 on colonic inflammation and epithelial barrier in dextran sulfate sodium(DSS)-induced colitis in mice.METHODS:Experimental colitis was induced by administration of 5% DSS for 7 d,and assays performed on intestinal segments from the ileocecal valve to the anus.Colonic morphology was examined by hematoxylin and eosin staining.Colonic cytokines were determined by enzyme-linked immunosorbent assay.Myeloperoxidase(MPO) activity(indicator of inflammatory infiltration) was observed spectrophotometrically.Gut permeability was assessed by mucosal-to-serosal clearance of fluorescein isothiocyanate-conjugated dextran 4000(FD4) in everted gut sacs.The apoptosis of colonic epithelium was assessed by Hoechst-33342 staining.To further elucidate the role of CXCR4 in colonic inflammation,we also investigated the effect of AMD3100 on migration and cytokine production of isolated peripheral blood mononuclear cells(PBMCs).RESULTS:DSS-induced colitis was characterized by morphologic changes,as well as increased colonic cytokines,inflammatory infiltration,epithelial apoptosis,and intestinal permeability in mice.In AMD3100-treated mice,epithelial destruction,inflammatory infiltration,and submucosal edema were markedly reduced;colonic tumor necrosis factor-α(TNF-α),interleukin-6(IL-6) and interferon-γ(IFN-γ) levels,as well as MPO activity were significantly decreased.Increased intestinal permeability in DSS-treated mice was signif icantly reduced by AMD3100.The number of apoptotic cells in colitis mice was markedly increased after DSS administration,and decreased when treated with the CXCR4 antagonist AMD3100.In pre-activated PBMCs,CXCL12 stimulation signif icantly increased the migration of PBMCs,and was inhibited by AMD3100.Moderately increased TNF-α,IL-6,and IFN-γ from CXCL12-treated PBMCs were also reduced by AMD3100.CONCLUSION:The CXCR4 antagonist AMD3100 exerts therapeutic effects on experimental colitis by inhibiting colonic inflammation and enhancing epithelial barrier integrity.

C-X3-C motif chemokine ligand 1/receptor 1 regulates the M1 polarization and chemotaxis of macrophages after hypoxia/reoxygenation injury

Background:Macrophages play an important role in renal ischemia reperfusion injury,but the functional changes of macrophages under hypoxia/reoxygenation and the related mechanism are unclear and need to be further clarified.Methods:The effects of hypoxia/reoxygenation on functional characteristics of RAW264.7 macrophages were analyzed through the protein expression detection of pro-inflammatory factors TNF-αand CD80,anti-inflammatory factors ARG-1 and CD206.The functional implications of C-X3-C motif chemokine receptor 1(CX3CR1)down-regulation in hypoxic macrophages were explored using small interfering RNA technology.Significance was assessed by the parametrict-test or nonparametric Mann-Whitney test for two group comparisons,and a one-way ANOVA or the Kruskal-Wallis test for multiple group comparisons.Results:Hypoxia/reoxygenation significantly increased the protein expression of M1-related pro-inflammatory factors TNF-α,CD80 and chemokine C-X3-C motif chemokine ligand 1(CX3CL1)/CX3CR1 and inhibited the protein expression of M2-related anti-inflammatory factors ARG-1 and CD206 in a time-dependent manner in RAW264.7 cells.However,the silencing of CX3CR1 in RAW264.7 cells using specific CX3CR1-siRNA,significantly attenuated the increase in protein expression of TNF-α(P<0.05)and CD80(P<0.01)and the inhibition of ARG-1(P<0.01)and CD206(P<0.01)induced by hypoxia/reoxygenation.In addition,we also found that hypoxia/reoxygenation could significantly enhance the migration(2.2-fold,P<0.01)and adhesion capacity(1.5-fold,P<0.01)of RAW264.7 macrophages compared with the control group,and CX3CR1-siRNA had an inhibitory role(40%and 20%reduction,respectively).For elucidating the mechanism,we showed that the phosphorylation levels of ERK(P<0.01)and the p65 subunit of NF-κB(P<0.01)of the RAW264.7 cells in the hypoxic/reoxygenation group were significantly increased,which could be attenuated by down-regulation of CX3CR1 expression(P<0.01,both).ERK inhibitors also significantly blocked the effects of hypoxic/reoxygenation on the protein expression of M1-related pro-inflammatory factors TNF-α,CD80 and M2-related anti-inflammatory factors ARG-1 and CD206.Moreover,we found that conditioned medium from polarized M1 macrophages induced by hypoxia/reoxygenation,notably increased the degree of apoptosis of hypoxia/reoxygenation-induced TCMK-1 cells,and promoted the protein expression of pro-apoptotic proteins bax(P<0.01)and cleaved-caspase 3(P<0.01)and inhibited the expression of anti-apoptotic protein bcl-2(P<0.01),but silencing CX3CR1 in macrophages had a protective role.Finally,we also found that the secretion of soluble CX3CL1 in RAW264.7 macrophages under hypoxia/reoxygenation was significantly increased.Conclusions:The findings suggest that hypoxia/reoxygenation could promote M1 polarization,cell migration,and adhesion of macrophages,and that polarized macrophages induce further apoptosis of hypoxic renal tubular epithelial cells by regulating of CX3CL1/CX3CR1 signaling pathway.

Effects of Curcumin on Pain Threshold and on the Expression of Nuclear Factor κ B and CX3C Receptor 1 after Sciatic Nerve Chronic Constrictive Injury in Rats

Objective：To investigate the effects of curcumin on pain threshold and the expressions of nuclear factorκB（NF-κB）and CX3C chemokine receptor 1（CX3CR1）in spinal cord and dorsal root ganglion（DRG）of the rats with sciatic nerve chronic constrictive injury.Methods：One hundred and twenty male Sprague Dawley rats,weighing 220-250 g,were randomly divided into 4 groups.Sham surgery（sham）group：the sciatic nerves of rats were only made apart but not ligated;chronic constrictive injury（CCI）group：the sciatic nerves of rats were only ligated without any drug treatment;curcumin treated injury（Cur）model group：the rats were administrated with curcumin 100 mg/（kg·d）by intraperitoneal injection for 14 days after CCI;solvent control（SC）group：the rats were administrated with the solvent at the same dose for 14 days after CCI.Thermal withdrawal latency（TWL）and mechanical withdrawal threshold（MWT）of rats were respectively measured on pre-operative day 2 and postoperative day 1,3,5,7,10 and 14.The lumbar segment L4-5 of the spinal cord and the L4,L5 DRG was removed at post-operative day 3,7 and 14.The change of nuclear factorκB（NF-κB）p65 expression was detected by Western blotting while the expression of CX3CR1 was determined by immunohistochemical staining.Results：Compared with the sham group,the TWL and MWT of rats in the CCI group were significantly decreased on each post-operative day（P〈0.01）,which reached a nadir on the 3rd day after CCI,and the expressions of NF-κB p65and CX3CR1 were markedly increased in spinal cord dorsal horn and DRG.In the Cur group,the TWL of rats were significantly increased than those in the CCI group on post-operative day 7,10 and 14（P〈0.05）and MWT increased than those in the CCI group on post-operative day 10 and 14（P〈0.05）.In addition,the administration of curcumin significantly decreased the positive expressions of NF-κB p65 and CX3CR1 in spinal cord and DRG（P〈0.05）.Conclusion：Our study suggests that curcumin could ameliorate the CCI-induced neuropathic pain,probably through inhibiting CX3CR1 expression by the activation of NF-k B p65 in spinal cord and DRG.

Biphasic modulation of chemerin peptide-induced calcium flux and ERK phosphorylation by amyloid beta peptide

OBJECTIVE The chemokine-like receptor 1(CMKLR1,Chem R23) is a functional receptor for chemerin,the chemerin-derived nonapeptide(C9),and the amyloid β peptide 1-42(Aβ_(42)).Because these peptides share little sequence homology,studies were conducted to investigate their pharmacological properties and regulation at CMKLR1.METHODS Cells expressing CMKLR1 were incubated with Aβ_(42) before stimulation with a strong agonist,the C9 peptide.Calcium mobilization,c AMP inhibition and MAP kinase activation were measured.Intramolecular FRET were determined using CMKLR1 constructs with an ECFP attached to the C-terminus and a Fl As H binding motif embedded in the first intracellular loop(IL1).RESULTS Binding of both Aβ_(42) and the C9 peptide induced CMKLR1 internalization,but only the Aβ_(42)-induced receptor internalization involved clathrin-coated pits.Likewise,Aβ_(42) but not C9 stimulated β-arrestin 2 translocation to plasma membranes.A robust Ca^(2+)flux was observed following C9 stimulation,whereas Aβ_(42) was ineffective even at micromolar concentrations.Despite its low potency in calcium mobilization assay,Aβ_(42) was able to alter C9-induced Ca^(2+) flux in dose-dependent manner:a potentiation effect at 100 pmol·L^(-1) of Aβ_(42) was followed by a suppression at 10 nmol·L^(-1) and further potentiation at 1 μmol·L^(-1).This unusual and biphasic modulatory effect was also seen in the C9-induced ERK phosphorylation but the dose curve was opposite to that of Ca^(2+) flux and c AMP inhibition,suggesting a reciprocal regulatory mechanism.Intramolecular FRET assay confirmed that Aβ_(42) modulates CMKLR1 rather than its downstream signaling pathways.CONCLUSION These findings suggest Aβ_(42) as an allosteric modulator that can both positively and negatively regulate the activation state of CMKLR1 in a manner that differs from existing allosteric modulatory mechanisms.

Genotypes and polymorphisms of mutant CCR5-△32,CCR2-64I and SDF1-3'A HIV-1 resistance alleles in indigenous Han Chinese

Objective To evaluate the frequencies and polymorphisms of CCR5-△32,CCR2-641 and SDF1-3'A alleles conferring resistance to HIV-1 infection in Chinese population from Han ethnic origin.Methods This cohort was comprised of 1251 subjects(915 men and 336 women)aged 15 -80 years and none was HIV-1 positive.Genotyping of allelic CCR5-△32,CCR2-641 and SDF1-3' A variants was performed using PCR or PCR/RFLP assay,and further confirmed by direct DNA sequencing.Results Our finding shows that the△32 deletion mutation in the CCR5 gene does occur in this population and can be inherited in a Mendelian fashion in indigenous Han Chinese at a very low frequency of 0.00119(n= 1254).The frequencies of mutant CCR2-641 and SDF1-3'A alleles were 0.20023(n = 1251)and 0.2873(n = 893),in this population,which are higher than those found in American Caucasians.Furthermore the polymorphisms of CCR2-641 and SDF1-3' A alleles in the Han Chinese population were different from those in American Caucasians.Statistical analysis showed that the genotype distribution of CCR5-△32,CCR2-641 and SDF1-3' A alleles was in equilibrium according to the Hardy-Weinberg equation.Conclusion The CCR5-△32 mutation may not be a major resistant factor against HIV-1 infection in indigenous Han Chinese.The significance of higher frequencies of CCR2-641 and SDF1-3' A alleles (0.20023 and 0.2791)in the Han population remains to be clarified in HIV-1-positive carriers and AIDS patients.