Overexpression of mitogen-activated protein kinase phosphatase-1 in endothelial cells reduces blood-brain barrier injury in a mouse model of ischemic stroke

Ischemic stroke can cause blood-brain barrier(BBB)injury,which worsens brain damage induced by stroke.Abnormal expression of tight junction proteins in endothelial cells(ECs)can increase intracellular space and BBB leakage.Selective inhibition of mitogen-activated protein kinase,the negative regulatory substrate of mitogen-activated protein kinase phosphatase(MKP)-1,improves tight junction protein function in ECs,and genetic deletion of MKP-1 aggravates ischemic brain injury.However,whether the latter affects BBB integrity,and the cell type-specific mechanism underlying this process,remain unclear.In this study,we established an adult male mouse model of ischemic stroke by occluding the middle cerebral artery for 60 minutes and overexpressed MKP-1 in ECs on the injured side via lentiviral transfection before stroke.We found that overexpression of MKP-1 in ECs reduced infarct volume,reduced the level of inflammatory factors interleukin-1β,interleukin-6,and chemokine C-C motif ligand-2,inhibited vascular injury,and promoted the recovery of sensorimotor and memory/cognitive function.Overexpression of MKP-1 in ECs also inhibited the activation of cerebral ischemia-induced extracellular signal-regulated kinase(ERK)1/2 and the downregulation of occludin expression.Finally,to investigate the mechanism by which MKP-1 exerted these functions in ECs,we established an ischemic stroke model in vitro by depriving the primary endothelial cell of oxygen and glucose,and pharmacologically inhibited the activity of MKP-1 and ERK1/2.Our findings suggest that MKP-1 inhibition aggravates oxygen and glucose deprivation-induced cell death,cell monolayer leakage,and downregulation of occludin expression,and that inhibiting ERK1/2 can reverse these effects.In addition,co-inhibition of MKP-1 and ERK1/2 exhibited similar effects to inhibition of ERK1/2.These findings suggest that overexpression of MKP-1 in ECs can prevent ischemia-induced occludin downregulation and cell death via deactivating ERK1/2,thereby protecting the integrity of BBB,alleviating brain injury,and improving post-stroke prognosis.

Mitogen-activated protein kinase cascades in plant signaling

Mitogen-activated protein kinase(MAPK)cascades are key signaling modules downstream of receptors/sensors that perceive either endogenously produced stimuli such as peptide ligands and damage-associated molecular patterns(DAMPs)or exogenously originated stimuli such as pathogen/microbe-associated molecular patterns(P/MAMPs),pathogen-derived effectors,and environmental factors.In this review,we provide a historic view of plant MAPK research and summarize recent advances in the establishment of MAPK cascades as essential components in plant immunity,response to environmental stresses,and normal growth and development.Each tier of the MAPK cascades is encoded by a small gene family,and multi ple members can function redundantly in an MAPK cascade.Yet,they carry out a diverse array of biological functions in plants.How the signaling specificity is achieved has become an interesting topic of MAPK research.Future investigations into the molecular mechanism(s)underlying the regulation of MAPK activation including the activation kinetics and magnitude in response to a stimulus,the spatiotemporal expression patterns of all the components in the signaling pathway,and functional characterization of novel MAPK substrates are central to our understanding of MAPK functions and signaling specificity in plants.

Overexpression of Arabidopsis thaliana cysteine2/histidine2-type transcription factor 6 gene enhances plant resistance to a bacterial pathogen

Transcription factors can be used to engineer plants for enhanced productivity.However,the mechanism(s)by which the C2H2-type zinc fi nger transcription factor enhances pathogen resistance in cells is not fully understood.Here,Agrobacterium tumefaciens carrying the gene for Arabidopsis thaliana cysteine2/histidine2-type transcription factor 6(ZAT6)was used to engineer rice(Oryza sativa L.),cotton(Gossypium hirsutum L.),and slash pine(Pinus elliottii Engelm.)to generate transgenic cell lines.Transgenic cells were then inoculated with the pathogenic bacterium Pseudomonas syringae.Compared to the control,cell viability of transgenic cells increased 39–47%and growth rate increased 9–15%by 7 days after inoculation in rice,cotton and slash pine.Acid phosphatase activity and alkaline phosphatase activity and transcript levels of Ca 2+-dependent protein kinase genes OsCPK1,OsCPK2,OsCPK6,and OsCPK8 and mitogen-activated protein kinase genes OsMAPK1,OsMAPK2,OsMAPK3,and OsMAPK8 increased signifi cantly in transgenic rice cells by 3 day after inoculation,and extracellular pH had decreased by 10–14%by 96 min after inoculation in transgenic rice,cotton and slash pine cells.These results suggest that ZAT6 enhances P.syringae resistance in plant cells by modulating transcription of CPK and MAPK and oxidase activity.