Objective To investigate the role of autophagy involving the protein kinase B/sterol regulatory element binding protein 1(Akt/SREBP-1)signaling pathway in diabetic retinopathy(DR).Methods DR rat models were estab-lished via the intraperitoneal injection of streptozotocin.Rats were randomized into control(normal rats)and DM-DR groups(DR rats).The expression of autophagy-related proteins(autophagy markers LC3-Ⅱ and LC3-Ⅰ,autophagy specific substrate p62,and autophagy-related protein Beclin1)in rat retinas was compared between the two groups.Rats were di-vided into control B(normal rats injected with 1 μL saline),DR(DR rats injected with 1 μL saline),DR+si-NC(DR rats injected with 1 μL of the negative control siRNA),and DR+si-SREBP-1 groups(DR rats injected with 1 μL of the SREBP-1 siRNA).All interventions were given 1 day before modeling and 8 weeks after modeling.Akt/SREBP-1 expression and retinal ganglion cell(RGC)survival were compared among groups.R28 rat retinal precursor cells were classified into con-trol C(normal glucose,24 h),HG(high glucose,24 h),HG+si-NC(si-NC transfection+high glucose,24 h),and HG+si-SREBP-1 groups(si-SREBP-1 transfection+high glucose,24 h).The expression of autophagy-related proteins and au-tophagosome-lysosome fusion were compared among groups.Western blot and immunofluorescence were used to examine the expression of Akt,SREBP-1 and autophagy-related proteins.Results The relative expression of Beclin1 and p62 pro-teins and the LC3-Ⅱ/Ⅰ ratio in the DM-DR group were significantly higher than those in the control group 1 and 8 weeks after modeling(all P＜0.001).Compared with the control B group,the DR group exhibited elevated SREBP-1 and reduced Akt protein levels 1 and 8 weeks after modeling(all P＜0.01).RGC counts in the DR and DR+si-NC groups were significantly lower than those in the control B group(P＜0.001).The RGC count in the DR+si-SREBP-1 group was significantly higher than that in the DR+si-NC group(P＜0.001).Compared with those in the control C group,the Beclin1 and p62 protein levels and the LC3-Ⅱ/Ⅰ ratio were increased in the HG and HG+si-NC groups(all P＜0.01).Compared with those in the HG+si-NC group,the Beclin1 and p62 protein levels and the LC3-Ⅱ/Ⅰ ratio were reduced in the HG+si-SREBP-1 group(all P＜0.05).The HG and HG+si-NC groups showed significantly more LC3B/LAMP1 dual-positive puncta than the control C group(P＜0.001).The HG+si-SREBP-1 group showed significantly less LC3B/LAMP1 dual-positive puncta than the HG+si-NC group(P＜0.001).Conclusion SREBP-1 knockdown enhances autophagic flux in early DR to attenuate RGC loss.Thus,the Akt/SREBP-1 axis represents a promising therapeutic target for DR.

Objective To investigate the role of autophagy involving the protein kinase B/sterol regulatory element binding protein 1(Akt/SREBP-1)signaling pathway in diabetic retinopathy(DR).Methods DR rat models were estab-lished via the intraperitoneal injection of streptozotocin.Rats were randomized into control(normal rats)and DM-DR groups(DR rats).The expression of autophagy-related proteins(autophagy markers LC3-Ⅱ and LC3-Ⅰ,autophagy specific substrate p62,and autophagy-related protein Beclin1)in rat retinas was compared between the two groups.Rats were di-vided into control B(normal rats injected with 1 μL saline),DR(DR rats injected with 1 μL saline),DR+si-NC(DR rats injected with 1 μL of the negative control siRNA),and DR+si-SREBP-1 groups(DR rats injected with 1 μL of the SREBP-1 siRNA).All interventions were given 1 day before modeling and 8 weeks after modeling.Akt/SREBP-1 expression and retinal ganglion cell(RGC)survival were compared among groups.R28 rat retinal precursor cells were classified into con-trol C(normal glucose,24 h),HG(high glucose,24 h),HG+si-NC(si-NC transfection+high glucose,24 h),and HG+si-SREBP-1 groups(si-SREBP-1 transfection+high glucose,24 h).The expression of autophagy-related proteins and au-tophagosome-lysosome fusion were compared among groups.Western blot and immunofluorescence were used to examine the expression of Akt,SREBP-1 and autophagy-related proteins.Results The relative expression of Beclin1 and p62 pro-teins and the LC3-Ⅱ/Ⅰ ratio in the DM-DR group were significantly higher than those in the control group 1 and 8 weeks after modeling(all P＜0.001).Compared with the control B group,the DR group exhibited elevated SREBP-1 and reduced Akt protein levels 1 and 8 weeks after modeling(all P＜0.01).RGC counts in the DR and DR+si-NC groups were significantly lower than those in the control B group(P＜0.001).The RGC count in the DR+si-SREBP-1 group was significantly higher than that in the DR+si-NC group(P＜0.001).Compared with those in the control C group,the Beclin1 and p62 protein levels and the LC3-Ⅱ/Ⅰ ratio were increased in the HG and HG+si-NC groups(all P＜0.01).Compared with those in the HG+si-NC group,the Beclin1 and p62 protein levels and the LC3-Ⅱ/Ⅰ ratio were reduced in the HG+si-SREBP-1 group(all P＜0.05).The HG and HG+si-NC groups showed significantly more LC3B/LAMP1 dual-positive puncta than the control C group(P＜0.001).The HG+si-SREBP-1 group showed significantly less LC3B/LAMP1 dual-positive puncta than the HG+si-NC group(P＜0.001).Conclusion SREBP-1 knockdown enhances autophagic flux in early DR to attenuate RGC loss.Thus,the Akt/SREBP-1 axis represents a promising therapeutic target for DR.

Objective To investigate the role of growth arrest-specific 6(Gas6)/Mer tyrosine kinase(MerTK)signaling pathway in ferroptosis in diabetes retinopathy(DR).Methods Human retinal pigment epithelial cells(ARPE-19)were divided into control group,HG group,HG+sh-Gas6 group,and HG+Gas6 group.Cells were exposed to 25 mmol/L D-glucose for simulating an in vitro hyperglycemic(HG)environment.The control group was exposed to a 20 mmol/L mannitol+5.5 mmol/L glucose environment.Rats were randomly divided into normal control group,DR group,and DR+Gas6 group,with 20 rats in each group.A DR model was established by intra-peritoneal injection of STZ solution.Cell proliferation was evaluated using the cell count kit 8(CCK-8)assay.Lip-id reactive oxygen species(ROS)levels were measured by flow cytometry,and levels of malondialdehyde(MDA),superoxide dismutase(SOD),and glutathione peroxidase(GSH-Px)were measured by biochemical assays to eval-uate iron death.The expression of Gas6 and MerTK proteins was analyzed by Western blot.Results Compared with HG group,the cell viability,SOD,GSH-Px levels in HG+Gas6 group increased significantly(P＜0.05),while the levels of lipid-ROS and MDA decreased significantly(P＜0.05).In HG+sh-Gas6 group,the cell via-bility,SOD and GSH-Px levels decreased significantly(P＜0.05),while the levels of lipid-ROS and MDA in-creased significantly(P＜0.05).In addition,the expression of GPX4 protein in HG+Gas6 group was significant-ly higher than that in HG group(P＜0.05),and the expression of GPX4 protein in HG+sh-Gas6 group was sig-nificantly lower than that in HG group(P＜0.05).Compared with the control group,the average thickness of reti-nal nerve fiber layer in DR group significantly decreased(P＜0.05),while that in DR+Gas6 group increased sig-nificantly(P＜0.05).In addition,the levels of MDA and iron in retinal pigment epithelium(RPE)tissues of DR+Gas6 group decreased significantly(P＜0.05),while the levels of GSH and the expressions of Gas6,MerTK and GPX4 proteins increased significantly(P＜0.05).Conclusion HG treatment accelerates the clearance of GPX4 by inhibiting the Gas6/MerTK signaling pathway,inducing ferroptosis and cell growth inhibition in ARPE-19 cells.In addition,up-regulating the expression of Gas6/MerTK signal in DR rat retina can alleviate ferroptosis and oxidative stress in RPE tissue,and help to restore the average retinal nerve fiber layer thickness.

Beta-lactams are the most widely used antibiotics. One of the principle mechanisms for Gram-negative bacteria to resist β-lactams is by producing β-lactamases that degrade β-lactams. This review highlights two regulatory mechanisms for inducing β-lactamase in Gram-negative bacteria. In the ampR-ampC paradigm, the induction of β-lactamase is intimately linked to peptidoglycan recycling. AmpR, a LysR-type transcriptional regulator, plays a central role in regulating expression of β-lactamase. Recent studies found that two-component signal transduction pathway is activated by β-lactams, which in turn induces the expression of β-lactamase. Finally, we discussed the future research directions in β-lactam resistance in Gram-negative bacteria.