title: Temporal expression of cytokines and signal transducer and activator of transcription factor 3 activation after neonatal hypoxia/ischemia in mice.
abstract: Hypoxia/ischemia (HI) is a prevalent reason for neonatal brain injury with inflammation being an inevitable phenomenon following such injury; but there is a scarcity of data regarding the signaling pathway involved and the effector molecules. The signal transducer and activator of transcription factor 3 (STAT3) is known to modulate injury following imbalance between pro- and anti-inflammatory cytokines in peripheral and central nervous system injury making it a potential molecule for study. The current study investigates the temporal expression of interleukin (IL)-6, IL-1β, tumor necrosis factor-α, IL-1ra, IL-4, IL-10, IL-13 and phosphorylated STAT3 (pSTAT3) after carotid occlusion and hypoxia (8% O2, 55 min) in postnatal day 7 C57BL/6 mice from 3 h to 21 days after hypoxia. Protein array illustrated notable changes in cytokines expressed in both hemispheres in a time-dependent manner. The major pro-inflammatory cytokines showing immediate changes between ipsi- and contralateral hemispheres were IL-6 and IL-1β. The anti-inflammatory cytokines IL-4 and IL-13 demonstrated a delayed augmentation with no prominent differences between hemispheres, while IL-1ra showed two distinct peaks of expression spread over time. We also illustrate for the first time the spatiotemporal activation of pSTAT3 (Y705 phosphorylation) after a neonatal HI in mice brain. The main regions expressing pSTAT3 were the hippocampus and the corpus callosum. pSTAT3+ cells were mostly a subpopulation of activated astrocytes (GFAP+) and microglia/macrophages (F4/80+) seen only in the ipsilateral hemisphere at most time points studied (till 7 days after hypoxia). The highest expression of pSTAT3+ cells was observed to be around 24-48 h, where the presence of pSTAT3+ astrocytes and pSTAT3+ microglia/macrophages was seen by confocal micrographs. In conclusion, our study highlights a synchronized expression of some pro- and anti-inflammatory cytokines, especially in the long term not previously defined. It also points towards a significant role of STAT3 signaling following micro- and astrogliosis in the pathophysiology of neonatal HI-related brain injury. In the study, a shift from pro-inflammatory to anti-inflammatory cytokine profile was also noted as the injury progressed. We suggest that while designing efficient neuroprotective therapies using inflammatory molecules, the time of intervention and balance between the pro- and anti-inflammatory cytokines must be considered.
authors.affiliation: Department of Cell Biology, Physiology and Immunology, Universitat Autonoma Barcelona, Bellaterra, Spain. Kalpana.Shrivastava@uab.cat
authors.forename: K
authors.initials: K
authors.lastname: Shrivastava
authors.forename: G
authors.initials: G
authors.lastname: Llovera
authors.forename: M
authors.initials: M
authors.lastname: Recasens
authors.forename: M
authors.initials: M
authors.lastname: Chertoff
authors.forename: L
authors.initials: L
authors.lastname: Giménez-Llort
authors.forename: B
authors.initials: B
authors.lastname: Gonzalez
authors.forename: L
authors.initials: L
authors.lastname: Acarin
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism*; D016207:Cytokines / Q000096:biosynthesis*; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism* / Q000473:pathology; D007150:Immunohistochemistry; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D050796:STAT3 Transcription Factor / Q000096:biosynthesis*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D016207:Cytokines; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse