Scutellaria barbata attenuates diabetic retinopathy by preventing retinal inflammation and the decreased expression of tight junction protein

AIM： To observe the attenuation of ethanol extract of Herba Scutellaria barbata （SE） against diabetic retinopathy （DR） and its engaged mechanism. METHODS： C57BL/6J mice were intraperitoneally injected with streptozotocin （STZ, 55 mg/kg） for 5 consecutive days to induce diabetes, The diabetic mice were orally given with SE （100, 200 mg/kg） for lmo at lmo after STZ injection. Blood-retinal barrier （BRB） breakdown was detected by using Evans blue permeation assay. Real-time polymerase chain reaction （RT-PCR）, Western blot and immunofiuorescence staining were used to detect mRNA and protein expression. Enzyme-linked immunosorbent assay （ELISA） was used to detect serum contents of tumor necrosis factor-e （TNF-a） and interleukin （IL）-II. RESULTS： SE （100, 200 mg/kg） reversed the breakdown of BRB in STZ-induced diabetic mice. The decreased expression of retinal claudin-1 and claudin-19, which are both tight junction （T J） proteins, was reversed by SE. SE decreased the increased serum contents and retinal mRNA expression of TNF-a and IL-113. SE also decreased the increased retinal expression of intercellular cell adhesion molecule-1 （ICAM-1）. SE reduced the increased phosphorylation of nuclear factor kappa B （NFKB） p65 and its subsequent nuclear translocation in retinas from STZ- induced diabetic mice. Results of Western blot and retinal immunofluorescence staining of ionized calcium-binding adapter molecule 1 （Ibal） demonstrated that SE abrogated the activation of microglia cells in STZ-induced diabetic mice. CONCLUSION： SE attenuates the development of DR by inhibiting retinal inflammation and restoring the decreased expression of TJ proteins including claudin-1 and claudin-19.

Scutellarein alleviates the dysfunction of inner blood-retinal-barrier initiated by hyperglycemia-stimulated microglia cells

AIM:To investigate the alleviation of scutellarein(SN)against inner blood-retinal-barrier(iBRB)dysfunction in microglia cells stimulated by hyperglycemia and to elucidate the engaged mechanism.METHODS:Microglia BV2 cells were stimulated by using 25 mmol/L D-glucose.The same concentration of mannitol(25 mmol/L)was applied as an isotonic contrast.Real-time PCR,Western-blot assay and immunofluorescence staining assay was performed.The dysfunction of iBRB in vitro was detected by using transendothelial electrical resistance(TEER)assay.Additionally,the leakage of fluorescein isothiocyanate(FITC)-conjugated dextran(70 kDa)was detected.RESULTS:SN abrogated microglia BV2 cells activation and reduced the phosphorylated activation of extracellular signal-regulated protein kinase(ERK)1/2.SN also decreased the transcriptional activation of nuclear factorκB(NFκB)and the elevated expression of tumor necrosis factorα(TNFα),interleukin(IL)-6 and IL-1βin BV2 cells treated with D-glucose(25 mmol/L).SN attenuated iBRB dysfunction in human retinal endothelial cells(HRECs)or choroid-retinal endothelial RF/6 A cells when those cells were treated with TNFα,IL-1βor IL-6,or co-cultured with microglia cells stimulated by D-glucose.Moreover,SN restored the decreased protein expression of tight junctions(TJs)in TNFα-treated HRECs and RF/6 A cells.CONCLUSION:SN not only alleviate iBRB dysfunction via directly inhibiting retinal endothelial injury caused by TNFα,IL-1βor IL-6,but also reduce the release of TNFα,IL-1βand IL-6 from microglia cells by abrogating hyperglycemia-mediated the activation of microglia cells.