ABSTRACT
To explore the potential function of interleukin-13 (IL-13), lipopolysaccharide (LPS) or PBS as a control was unilaterally microinjected into striatum of rat brain. Seven days after LPS injection, there was a significant loss of neurons and microglial activation in the striatum, visualized by immunohistochemical staining against neuronal nuclei (NeuN) and the OX-42 (complement receptor type 3, CR3), respectively. In parallel, IL-13 immunoreactivity was increased as early as 3 days and sustained up to 7 days post LPS injection, compared to PBS-injected control and detected exclusively within microglia. Moreover, GFAP immunostaining and blood brain barrier (BBB) permeability evaluation showed the loss of astrocytes and disruption of BBB, respectively. By contrast, treatment with IL-13 neutralizing antibody (IL-13NA) protects NeuN + neurons against LPSinduced neurotoxicity in vivo . Accompanying neuroprotection, IL-13NA reduced loss of GFAP + astrocytes and damage of BBB in LPS-injected striatum. Intriguingly, treatment with IL-13NA produced neurotrophic factors (NTFs) on survived astrocytes in LPS-injected rat striatum. Taken together, the present study suggests that LPS induces expression of IL-13 on microglia, which contributes to neurodegeneration via damage on astrocytes and BBB disruption in the striatum in vivo.
ABSTRACT
Stroke causes systemic immunosuppression. T lymphocytes are involved in infarct size in the early stages of stroke. However, the phenotypes of T lymphocytes and their functions in peripheral immune organs and the brain have not been well analyzed in the acute and chronic phases of stroke. Here, we investigated pathological phenotypic alterations in the systemic immune response, especially changes in T lymphocytes, from one day to six months after ischemic stroke in mice. Impairment in thymocyte numbers, development, proliferation, and apoptosis were observed for up to two weeks. The number of mature T cells in the spleen and blood decreased and showed reduced interferon-γ production. Increased numbers of CD4-CD8-CD3+ double-negative T cells were observed in the mouse brain during the early stages of stroke, whereas interleukin (IL)-10+Foxp3+ regulatory T lymphocytes increased from two weeks during the chronic phase. These phenotypes correlated with body weight and neurological severity scores. The recovery of T lymphocyte numbers and increases in IL-10+Foxp3+ regulatory T lymphocytes may be important for long-term neurological outcomes. Dynamic changes in T lymphocytes between the acute and chronic phases may play different roles in pathogenesis and recovery. This study provides fundamental information regarding the T lymphocyte alterations from the brain to the peripheral immune organs following stroke.
ABSTRACT
Stroke causes systemic immunosuppression. T lymphocytes are involved in infarct size in the early stages of stroke. However, the phenotypes of T lymphocytes and their functions in peripheral immune organs and the brain have not been well analyzed in the acute and chronic phases of stroke. Here, we investigated pathological phenotypic alterations in the systemic immune response, especially changes in T lymphocytes, from one day to six months after ischemic stroke in mice. Impairment in thymocyte numbers, development, proliferation, and apoptosis were observed for up to two weeks. The number of mature T cells in the spleen and blood decreased and showed reduced interferon-γ production. Increased numbers of CD4-CD8-CD3+ double-negative T cells were observed in the mouse brain during the early stages of stroke, whereas interleukin (IL)-10+Foxp3+ regulatory T lymphocytes increased from two weeks during the chronic phase. These phenotypes correlated with body weight and neurological severity scores. The recovery of T lymphocyte numbers and increases in IL-10+Foxp3+ regulatory T lymphocytes may be important for long-term neurological outcomes. Dynamic changes in T lymphocytes between the acute and chronic phases may play different roles in pathogenesis and recovery. This study provides fundamental information regarding the T lymphocyte alterations from the brain to the peripheral immune organs following stroke.
ABSTRACT
Transient receptor potential vanilloid subtype 1 (TRPV1) on astrocytes prevents ongoing degeneration of nigrostriatal dopamine (DA) neurons in MPP⁺-lesioned rats via ciliary neurotrophic factor (CNTF). The present study determined whether such a beneficial effect of astrocytic TRPV1 could be achieved after completion of injury of DA neurons, rather than ongoing injury, which seems more relevant to therapeutics. To test this, the MPP⁺-lesioned rat model utilized here exhibited approximately 70~80% degeneration of nigrostriatal DA neurons that was completed at 2 weeks post medial forebrain bundle injection of MPP⁺. TRPV1 agonist, capsaicin (CAP), was intraperitoneally administered. CNTF receptor alpha neutralizing antibody (CNTFRαNAb) was nigral injected to evaluate the role of CNTF endogenously produced by astrocyte through TRPV1 activation on DA neurons. Delayed treatment of CAP produced a significant reduction in amphetamine-induced rotational asymmetry. Accompanying this behavioral recovery, CAP treatment increased CNTF levels and tyrosine hydroxylase (TH) activity in the substantia nigra pars compacta (SNpc), and levels of DA and its metabolites in the striatum compared to controls. Interestingly, behavioral recovery and increases in biochemical indices were not reflected in trophic changes of the DA system. Instead, behavioral recovery was temporal and dependent on the continuous presence of CAP treatment. The results suggest that delayed treatment of CAP increases nigral TH enzyme activity and striatal levels of DA and its metabolites by CNTF endogenously derived from CAP-activated astrocytes through TRPV1, leading to functional recovery. Consequently, these findings may be useful in the treatment of DA imbalances associated with Parkinson's disease.