Critical role of microglial CD40 in the maintenance of mechanical hypersensitivity in a murine model of neuropathic pain

We recently demonstrated a contributing role of spinal cord infiltrating CD4⁺ T lymphocytes in the maintenance of mechanical hypersensitivity in a rodent model of neuropathic pain, spinal nerve L5 transection (L5Tx). It has been demonstrated that microglia play a role in the etiology of pain states. We hypothesized that infiltrating CD4⁺ T lymphocytes communicate with microglia via a CD40‐CD154 interaction. Here, we investigated the role of CD40 in the development of mechanical hypersensitivity post‐L5Tx. CD40 KO mice displayed significantly decreased mechanical sensitivity compared with WT mice starting from day 5 post‐L5Tx. Using bone marrow chimeric mice, we further identified a pro‐nociceptive role of CNS microglial CD40 rather than the peripheral leukocytic CD40. Flow cytometric analysis determined a significant increase of CD40⁺ microglia in the ipsilateral side of lumbar spinal cord post‐L5Tx. Further, spinal cord proinflammatory cytokine (IL‐1β, IL‐6, IL‐12, and TNF‐α) profiling demonstrated an induction of IL‐6 in both WT and CD40 KO mice post‐L5Tx prior to the increase of microglial CD40 expression, indicating a CD40‐independent induction of IL‐6 following L5Tx. These data establish a novel role of microglial CD40 in the maintenance of nerve injury‐induced behavioral hypersensitivity, a behavioral sign of neuropathic pain.     

The contributing role of CD14 in toll-like receptor 4 dependent neuropathic pain

We have previously demonstrated that CNS toll-like receptor 4 (TLR4) plays a key role in the development of behavioral hypersensitivity in a rodent model of neuropathic pain, spinal nerve L5 transection (L5Tx). TLR4 is a well-known receptor for lipopolysaccharide (LPS) in innate immune responses. In the current study, we further investigated the role of CD14, an accessory molecule in the LPS-TLR4 signaling pathway, in the development of L5Tx-induced neuropathic pain. CD14 knockout (KO) mice displayed significantly decreased behavioral sensitivity (mechanical allodynia and thermal hyperalgesia) as early as day 1 post-L5Tx, indicating a nociceptive role of CD14. By flow cytometric analyses, we observed significantly elevated microglial surface CD14 expression in the ipsilateral lumbar spinal cord 3 days post-L5Tx, as well as remarkable increases in microglial size (via forward scatter (FSC)) and granularity (via side scatter (SSC)). Further, intrathecal injection of soluble CD14 induced significantly greater mechanical hypersensitivity in wild type (C3H/HeN) mice compared with TLR4-deficient (C3H/HeJ) mice. Together, these data demonstrate that CD14 plays a contributing role in TLR4-dependent nerve injury-induced neuropathic pain.     

Role of astrocytic S100beta in behavioral hypersensitivity in rodent models of neuropathic pain

S100beta is a calcium-binding peptide produced mainly by astrocytes that exerts paracrine and autocrine effects on neurons and glia. We have previously shown that S100beta is markedly elevated at the mRNA level in the spinal cord following peripheral inflammation, intraplantar administration of complete Freund's adjuvant in the rat. The purpose of the present study was to further investigate the role of astrocytic S100beta in mediating behavioral hypersensitivity in rodent models of persistent pain. First, we assessed the lumbar spinal cord expression of S100beta at the mRNA and protein level using real-time RT-PCR, Western blot and immunohistochemistry analysis following L5 spinal nerve transection in rats, a rodent model of neuropathic pain. Second, we assessed behavioral hypersensitivity (mechanical allodynia) in wild type and genetically modified mice lacking or overexpressing S100beta following L5 spinal nerve transection. Third, we assessed the expression level of S100beta protein in the CD1 wild type mice after nerve injury. We report that lumbar spinal S100beta mRNA steadily increased from days 4-28 after nerve injury. S100beta protein in the lumbar spinal cord was significantly increased in both rats and mice at day 14 following nerve injury as compared with sham control groups. S100beta genetically deficient mice displayed significantly increased tactile thresholds (reduced response to non-noxious stimuli) after nerve injury as compared with the wild type group. S100beta overexpressing mice displayed significantly decreased tactile threshold responses (enhanced response to non-noxious stimuli). Together, these results from both series of experiments using a peripheral nerve injury model in two different species implicate the involvement of glial-derived S100beta in the pathophysiology of neuropathic pain.     

Mouse strains that lack spinal dynorphin upregulation after peripheral nerve injury do not develop neuropathic pain

Several experimental models of peripheral neuropathy show that a significant upregulation of spinal dynorphin A and its precursor peptide, prodynorphin, is a common consequence of nerve injury. A genetically modified mouse strain lacking prodynorphin does not exhibit sustained neuropathic pain after nerve injury, supporting a pronociceptive role of elevated levels of spinal dynorphin. A null mutation of the gamma isoform of protein kinase C (PKCgamma KO [knockout]), as well as an inbred mouse strain, 129S6, also does not manifest behavioral signs of neuropathic pain following peripheral nerve injury. The objective of this study was to extend our observations to these genetic models to test the hypothesis that elevated levels of spinal dynorphin are essential for the maintenance of abnormal pain. In PKCgamma wild-type mice and the outbred mouse strain ICR, ligation of the L5 and L6 spinal nerves (SNL) elicited both tactile hypersensitivity and thermal hyperalgesia. Both strains showed a significant elevation in dynorphin in the lumbar spinal dorsal horn following SNL. Spinal administration of an anti-dynorphin A antiserum blocked the thermal and tactile hypersensitivity in both strains of mice. However, the PKCgamma KO mice and the 129S6 mice (which express PKCgamma) did not show abnormal pain after SNL; neither strain showed elevated levels of spinal dynorphin. The multiple phenotypic deficits in PKCgamma KO mice confound the interpretation of the proposed role of PKCgamma-expressing spinal neurons in neuropathic pain states. Additionally, the data show that the regulation of spinal dynorphin expression is a common critical feature of expression of neuropathic pain.     

Lymphocyte activation and hepatic cellular infiltration in immunocompetent mice infected by dengue virus

Activation and expansion of dengue virus-specific T cells and abnormal liver functions in dengue patients have been documented. However, it remains to be determined whether T cells are involved in the pathogenic mechanism of dengue virus infection. In this study, immunocompetent C57BL/6 mice were employed to study dengue virus-induced T cell activation. Mice were inoculated with 10(8) PFU dengue virus serotype 2 strain 16681 by the intravenous route. Dengue viral core RNA was detected by RT-PCR in mouse serum, liver, spleen, and brain at different time points after infection. Splenic T cells were activated as evidenced by their expression of CD69 and O-glycosylated CD43 at as early as day 3 after infection. Splenic T cell expression of O-glycosylated CD43 and IFN-gamma production coordinately peaked at day 5. Coincided with the peak of splenic T cell activation was hepatic lymphocyte infiltration and elevation of liver enzymes. Flow cytometric analysis revealed the infiltrating CD8(+) T cell to CD4(+) T cell ratio was 5/3. After a second inoculation of dengue virus, hepatic T cell infiltration and liver enzyme levels increased sharply. The infiltrating hepatic CD8(+) T cell to CD4(+) T cell ratio increased to 5.8/1. A strong correlation was found between T cell activation and hepatic cellular infiltration in immunocompetent mice infected with dengue virus. The kinetics of liver enzyme elevation also correlated with that of T cell activation. These data suggest a relationship between T cell infiltration and elevation of liver enzymes.     

Electroacupuncture inhibits cyclooxygenase-2 up-regulation in rat spinal cord after spinal nerve ligation

Electroacupuncture (EA) has long been used to treat pain including neuropathic pain, but its mechanisms remain to be delineated. Since cyclooxygenase-2 (COX-2) has been reported to increase in the spinal dorsal horn following spinal nerve ligation (SNL) and it may play a role in the neuropathic pain, we hereby tested the hypothesis that EA may affect COX-2 expression and hence neuropathic nociception after SNL. The results showed that EA (2 Hz) can significantly reduce mechanical and thermal hypersensitivity following lumbar L5 SNL in rats. Immunostaining demonstrated suppression of COX-2 expression in the spinal L4-L6 dorsal horn after EA. The present results suggest that EA may alleviate neuropathic hypersensitivity by, at least partially, inhibiting COX-2 expression in the spinal cord.     

Enhanced IL-10 production by CD4+ T cells primed in IL-15Rα-deficient mice

In this study, we investigated the functional outcomes of CD4(+) T cells primed in the absence of IL-15 transpresentation. Compared with their WT counterparts primed in WT mice, IL-15Rα KO CD4(+) T cells primed in KO mice were found to exclusively overproduce IL-10 upon in vitro restimulation(.) The comparable expression of IL-4 and Foxp3 in CD4(+) T cells primed in the WT and IL-15Rα KO mice indicated that this was neither due to T(H) 2- nor Treg cell-differentiation. IL-10 overproduction was also observed when OVA-specific TCR transgenic CD4(+) T (OT-II) cells were primed in KO mice, excluding an intrinsic deficiency of KO CD4(+) T cells. To investigate the WT and KO microenvironment, DCs from both WT and IL-15Rα KO mice were compared. DCs from both backgrounds were indistinguishable in their steady-state survival and in their expression of MHC class II and costimulatory molecules CD80, CD86, and CD40. However, IL-15Rα KO DCs primed OT-II cells in vitro to produce higher levels of IL-10 upon their restimulation. Additionally, IL-15Rα KO DCs produced significantly more IL-10 upon activation, and IL-10 neutralization during DC-mediated in vitro priming abolished IL-10 overproduction by CD4(+) T cells. Thus, IL-15Rα KO DCs provide an IL-10-enriched environment that preferentially primes CD4(+) T cells for more IL-10 production, highlighting a regulatory role for IL-15 transpresentation in CD4(+) T-cell priming.     

SNL大鼠CD4+ T细胞脊髓浸润及其分子机制研究

目的:研究脊神经结扎后,外周CD4+ T细胞迁移浸润至腰段脊髓及其分子调控机制.方法:选择健康成年清洁级雄性SD大鼠,随机分为脊神经结扎组(Tx 组)、假冒手术组(S组)、对照组(C组),用up-down方法测定50％机械缩足阈值(50％ MWT),并用FACS检测腰段脊髓CD4+ T细胞的浸润情况,RT-qPCR法测定脊髓中趋化因子CCL2、CCL5、CXCL10mRNA的表达水平,ELISA检测血清中相关细胞因子的含量.结果:与S组、C组相比,术后3 d,Tx组50％ MWT明显降低(P＜0.01),至术后14 d达最低值,S组与C组在各时间点均无明显差异(P＞0.05);术后7d,Tx组腰段脊髓浸润的CD4+ T细胞明显增加(P＜0.01),同时伴有CCL2、CCL5mRNA 的表达增加(P＜0.05);术后14 d,Tx组浸润的CD4+T 细胞较术后7d减少,虽高于S组、C组,但无统计学意义,上述各趋化因子的表达水平也无明显差异;术后7d、14 d,血清中各细胞因子的含量三组均无统计学意义.结论:神经损伤后,脊髓中高表达的趋化因子促进了外周CD4+ T细胞的中枢浸润,脊髓浸润的CD4+T 细胞可能与神经病理性疼痛的维持有关.     

Mechanical allodynia and spinal up-regulation of P2X4 receptor in experimental autoimmune neuritis rats

Experimental autoimmune neuritis (EAN) is the animal model of acute inflammatory demyelinating polyradiculoneuropathy (AIDP) that is the most common subtype of Guillain-Barre syndrome (GBS). While neuropathic pain is a common symptom of GBS, its underlying mechanisms remain elusive. Central sensitization, particularly spinal glia (microglia and astrocytes) activation, is important for the initiation and maintenance of neuropathic pain. P2X(4) receptor (P2X(4)R) is an ATP-gated ion channel and its spinal up-regulation has been found to be crucial for the development of neuropathic pain following peripheral nerve injury. The initiation of mechanical allodynia in rat EAN was observed at day 9 before the onset of neurological signs. Maximal level of mechanical allodynia was observed from days 17-19 and then a slow recovery, long after the cessation of typical neurological signs of EAN, until day 37 was observed. Expression of P2X(4)R in lumbar spinal cords was studied by immunohistochemistry. P2X(4)R immunoreactivity (IR) was mainly seen in gray matter, particularly in the dorsal horn. Accumulation of P2X(4)R(+) cells in the lumbar dorsal horn was observed at day 9, reached the maximal level at day 17 and remained elevated until day 37 after immunization. Furthermore, a negative correlation between the density of P2X(4)R(+) cells in the lumbar dorsal horn with mean hind-paw withdrawal threshold in EAN rats was seen, indicating that P2X(4)R might contribute to EAN mechanical allodynia. Double staining revealed that almost all P2X(4)R(+) cells co-expressed CD68, a marker for reactive microglia, but not the astrocyte marker, glial fibrillary acidic protein (GFAP). Our data demonstrate that EAN induces mechanical allodynia and P2X(4)R expression in spinal microglia, suggesting that EAN is a good animal model for neuropathic pain in polyneuropathy and spinal microglia activation might participate in EAN-induced neuropathic pain.     

The central role of CD30L/CD30 interactions in allergic rhinitis pathogenesis in mice

CD30 ligand (CD30L) plays an important role in the amplification and/or activation of effector CD4(+) T cells, irrespective of Th cell subset. To examine the role of CD30L in allergic rhinitis, we evaluated an OVA model of allergic rhinitis in CD30L knock out (KO) mice on a BALB/c background sensitized with OVA. Symptoms of allergic rhinitis such as eosinophil infiltration into the nasal mucosa were drastically diminished in OVA-sensitized CD30L KO mice following intranasal challenge with OVA. The levels of OVA-specific IgE in the sera and the Th2 response in nasopharynx-associated lymphoid tissues and cervical LNs of CD30L KO mice were significantly lower than those of WT mice following intranasal challenge with OVA. Intranasal administration of CD30-Ig during the effector phase with OVA significantly prevented the development of allergic rhinitis in WT mice. These results suggest that CD30L plays an important role in allergic rhinitis and that the inhibition of CD30L/CD30 signaling might be useful as a novel biological therapy for allergic rhinitis.     

Longitudinally extensive NMO spinal cord pathology produced by passive transfer of NMO-IgG in mice lacking complement inhibitor CD59

Spinal cord pathology with inflammatory, demyelinating lesions spanning three or more vertebral segments is a characteristic feature of neuromyelitis optica (NMO). NMO pathogenesis is thought to involve binding of immunoglobulin G anti-aquaporin-4 autoantibodies (NMO-IgG) to astrocytes, causing complement-dependent cytotoxicity (CDC) and secondary inflammation, demyelination and neuron loss. We investigated the involvement of CD59, a glycophosphoinositol (GPI)-anchored membrane protein on astrocytes that inhibits formation of the terminal C5b-9 membrane attack complex. CD59 inhibition by a neutralizing monoclonal antibody greatly increased NMO-IgG-dependent CDC in murine astrocyte cultures and ex vivo spinal cord slice cultures. Greatly increased NMO pathology was also found in spinal cord slice cultures from CD59 knockout mice, and in vivo following intracerebral injection of NMO-IgG and human complement. Intrathecal injection (at L5–L6) of small amounts of NMO-IgG and human complement in CD59-deficient mice produced robust, longitudinally extensive white matter lesions in lumbar spinal cord. Pathology was most severe at day 2 after injection, showing loss of AQP4 and GFAP, C5b-9 deposition, microglial activation, granulocyte infiltration, and demyelination. Hind limb motor function was remarkably impaired as well. There was partial remyelination and recovery of motor function by day 5. Our results implicate CD59 as an important modulator of the immune response in NMO, and provide a novel animal model of NMO that closely recapitulates human NMO pathology. Up-regulation of CD59 on astrocytes may have therapeutic benefit in NMO.     

坐骨神经选择性损伤痛模型小鼠脊髓背角线粒体解偶连蛋白UCP4的表达变化

目的:观察线粒体保护蛋白解偶联蛋白4(uncoupling protein 4,UCP4)在坐骨神经选择性损伤(sparednerve injury,SNI)模型小鼠脊髓背角中的表达变化。方法:健康C57BL/6小鼠分为假手术对照组(n=21)和坐骨神经分支选择性损伤SNI组(n=21),实验组损伤后饲养3,7,14 d。行为学采用测定小鼠热痛阈和Von Frey机械性痛阈;用免疫荧光组织化学染色法检测对比小鼠脊髓L3-6节段背角内UCP4免疫阳性细胞的数量。结果:SNI术后3 d,小鼠手术侧热痛阈和机械性痛阈明显低于假手术组,术后14 d达最低值。UCP4分布于正常小鼠脊髓背角,SNI后3 d损伤组小鼠脊髓背角中的UCP4表达降低,图像分析表明UCP4的光密度与对照组比较,差异有统计学意义(P<0.05);脊髓背角中UCP4的表达在14 d时其降低程度最明显,图像分析表明光密度与对照组、3d和7 d比较,差异均有统计学意义(P<0.05)。结论:SNI后脊髓背角线粒体保护蛋白UCP4表达降低可能参与神经病理性疼痛的中枢敏化过程。     

Different Trypanosoma cruzi strains promote neuromyopathic damage mediated by distinct T lymphocyte subsets

The proliferative response of CD4 and CD8 T lymphocytes obtained from C3H/HeN mice chronically infected with Trypanosoma cruzi strains that differ in virulence, tropism and immunogenicity, was assayed against skeletal muscle, sciatic nerve and spinal cord homogenates. Although both CD4 and CD8 T lymphocytes from mice infected with the RA strain strongly proliferated against the nervous system, no response against skeletal muscle antigens was detected. CD4 and CD8 T lymphocytes from mice infected with the K-98 clone (from CA-I strain) showed low proliferative response against all the antigens assayed. To determine whether the proliferation patterns showed correlation with T cell-mediated neuromuscular damage, passive cell transfer studies were performed. Fifteen days after transfer of CD4 T cells from RA-infected donors (CD4-RA), normal syngeneic recipients displayed exclusively nervous tissue damage, such as perineural, endoneural and/or meningeal inflammatory infiltrates, with predominance of CD4 T cells. Fifteen days after transfer of CD4 T lymphocytes from mice infected with K-98 (CD4-K98), recipients showed inflammatory infiltrates only in skeletal muscle, where CD4 T lymphocytes and macrophages were predominant cells. Recipients of CD8 T cells from RA-infected mice (CD8-RA) showed lesions in both spinal cord and sciatic nerves. Higher percentages of CD8 T cells were observed in comparison with the recipients of CD4-RA or CD4-K98. In contrast, CD8 T cells from K-98-infected donors (CD8-K98) did not induce tissue damage. These results provide evidence that mice infected with T. cruzi populations that differ in their biological characteristics show diverse immune mechanisms that may be involved in the pathogenesis of peripheral nervous system damage.     

IL-15 exacerbates collagen-induced arthritis with an enhanced CD4+ T cell response to produce IL-17

IL-15 is thought to be involved in the pathogenesis of rheumatoid arthritis (RA). We found that IL-15 plays an important role in the development of murine collagen-induced arthritis (CIA). The incidence and severity of CIA were slightly decreased in IL-15 KO mice but were increased in IL-15 Tg mice compared with wild-type (WT) mice. The levels of type II collagen (CII)-specific IL-17 production were significantly increased in IL-15 Tg mice compared with WT mice with CIA. Expression of IL-23R was up-regulated in CD4(+) T cells in IL-15 Tg mice but down-regulated in IL-15 KO mice compared with WT mice. In correlation with the expression levels of IL-23R, IL-17 production by CD4(+) T cells in response to exogenous IL-23 was increased in IL-15 Tg mice compared with WT mice. Furthermore, exogenous IL-15 synergized with IL-23 to induce CII-specific IL-17 production by CD4(+) T cells in vitro. Taken together, these results indicate that IL-15 plays an important role in the progression of CIA through increasing antigen-specific IL-17 production by CD4(+) T cells.     

CD4(+) and CD8(+) cells are key participants in the development of recurrent herpetic stromal keratitis in mice

Ocular herpes simplex virus (HSV) infection results in an immune-mediated inflammation of the corneal stroma known as herpetic stromal keratitis (HSK). Recurrent HSK is a common cause of virus-induced corneal blindness in humans. The role of CD4(+) and CD8(+) T cell subsets in the disease pathogenesis is ill defined and varies with the virus strain and host genetic background. To examine the contribution of T cell subsets to corneal disease, we studied the development of recurrent HSK in CD4 or CD8 gene knockout (KO) mice ocularly infected with HSV-1 McKrae strain. Following UV-B induced viral reactivation, corneal opacity in latently infected BALB/c (HSV sensitive) CD4 and CD8 KO mice was reduced compared to infected BALB/c mice with normal genotype. In contrast, opacity in C57BL/6 (HSV resistant) CD4 and CD8 KO latent mice did not differ from genetically normal latent mice. Virus-induced corneal opacity was not demonstrable in C57BL/6 CD4/CD8 double KO mice. Increased viral shedding, measured by reactivation rate, days shedding or viral titers, occurred in CD4 KO mice of both strains. Our findings indicate that both CD4(+) and CD8(+) cells play a role in the immunopathogenesis of recurrent HSK, and their role is dependent upon the host genetic profile.     

Role of the CD5 molecule on TCR gammadelta T cell-mediated immune functions: development of germinal centers and chronic intestinal inflammation

Although CD4(+) T cells form a major subset of TCRalphabeta T cells, only a small number of TCRgammadelta T cells express CD4. Factors contributing to the down-regulation of CD4(+) TCRgammadelta T cells have not been identified. The CD5 molecule is expressed on most TCRgammadelta T cells in the spleen, whereas only a few intestinal intraepithelial TCRgammadelta T cells express this molecule in wild-type mice and TCRbeta mutant (beta(-/-)) mice. Unexpectedly, in the present studies, the lack of CD5 led to a remarkable increase of a CD4(+) TCRgammadelta T cell subset in CD5(-/-)beta(-/-) mice. The CD4(+) TCRgammadelta T cells were also detectable in MHC II(-/-)CD5(-/-)beta(-/-) triple-mutant mice. This CD4(+) TCRgammadelta T cell subset provided help in Mycobacterium-induced germinal center (GC) formation and showed a T(h)-like cytokine profile. In contrast, CD5(+) TCRgammadelta T cells suppressed the CD4(+) TCRgammadelta T cell-mediated GC formation, presumably by eliminating this CD4(+) subset. Unlike intraepithelial gammadelta T cells, >30% of TCRgammadelta T cells in the colonic lamina propria (LP) expressed CD5. The lack of CD5 also led to increased numbers of CD4(+) TCRgammadelta T cells in the colonic LP and increased susceptibility to development of chronic colitis in beta(-/-) mice. Cell transfer studies suggest that CD5(+) TCRgammadelta T cells are capable of selectively eliminating CD4(+) TCRgammadelta T cells in the intestine. The CD4(+) TCRgammadelta T cells possess immune functions similar to CD4(+) TCRalphabeta T cells.     

The role of the N-methyl-D-aspartate receptor NR1 subunit in peripheral nerve injury-induced mechanical allodynia, glial activation and chemokine expression in the mouse

The N-methyl-d-aspartate receptor (NMDAR) has been strongly implicated in mechanisms of persistent pain states. The purpose of the present study was to determine whether the NMDAR NR-1, a key subunit in regulation of NMDAR channel complex is directly contributing to the onset and propagation of peripheral nerve injury-induced allodynia and whether N-methyl-d-aspartate (NMDA) signaling interacts with spinal chemokine (chemotactic cytokines) expression and glial activation. We used genetically engineered male mice that had their normal NR1 gene knocked out and expressed a modified NR1 gene at either normal level (NR1 +/+, wild type) or at a low level (NR1+/-, knock down). Each mouse underwent a peripheral nerve injury in which the lumbar 5 spinal segment (L5) nerve was transected. Mechanical allodynia was assessed using 0.008 and 0.015 g von Frey filaments on days 1, 3, 5, 7, 10, 14, 17 and 21 post-surgery. Mice were killed on day 21 and the harvested L5 spinal cord was analyzed for chemokine expression using RNAse protection assay. In a separate study, glial expression using immunohistochemistry was assessed in both groups 7 days following peripheral nerve injury. The NR1+/- mice displayed decreased mechanical allodynia in comparison to their wild type counterparts. However, even with dramatically impaired NMDA receptor signaling, there was still evidence of tactile hypersensitivity. Using the RPA analysis, we found decreases in mRNA chemokine expression in the NR1+/- mice as compared with NR1+/+ mice. There were no apparent differences in microglial or astrocytic expression between the wild type and knock down mice. These data provide important insights into the cascade of events involving the dynamic interaction between NMDAR function and spinal chemokine and glial production in neuropathic pain states. The results support the findings that chemokine signaling releases glutamate in the spinal cord.     

Importance of immune deviation toward Th1 in the early immunopathogenesis of human T-lymphotropic virus type I-associated myelopathy

Although the principal neuropathological feature of human T-lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM) is chronic inflammation of the spinal cord, characterized by perivascular cuffing of mononuclear cells accompanied by parenchymal lymphocytic infiltration, the precise mechanisms by which HTLV-I infection causes chronic inflammation of the spinal cord are still obscure. In patients with HAM, peripheral blood CD4(+)T lymphocytes, particularly HTLV-I-infected CD4(+)T lymphocytes, have increased adherent activity to endothelial cells and transmigrating activity through basement membranes. In addition, the profile of cytokine expression suggests increased numbers of Th1 cells in peripheral blood CD4(+)T lymphocytes of patients with HAM. These findings strongly suggest that immune deviation toward Th1, which might be based on high viral load of HTLV-I, plays an important role in tissue damage in the central nervous system of patients with HAM. We herein emphasize the importance of activated Th1 cells as the first trigger in the immunopathogenesis of HAM.     

Age-related changes in the occurrence and characteristics of thymic CD4(+) CD25(+) T cells in mice

Natural regulatory CD4(+) CD25(+) T cells play an important role in preventing autoimmunity by maintaining self-tolerance. They express CD25 constitutively and are produced in the thymus as a functionally mature T-cell population. Changes in the potential of these cells to regulate the activity of conventional effector lymphocytes may contribute to an increased susceptibility to infection, cancer and age-associated autoimmune diseases. In this study we demonstrated that the thymi of aged mice are populated by a higher percentage of CD4(+) CD25(+) thymocytes than in young animals. The expression of several surface markers (CD69, CD5, CD28, CTLA-4, CD122, FOXP3), usually used to characterize the phenotype of CD4(+) CD25(+) T regulatory cells, was compared between young and aged mice. We also examined the ability of sorted thymus-deriving regulatory T cells of young and aged BALB/c mice to inhibit the proliferation of lymph node lymphocytes activated in vitro. Natural regulatory T cells isolated from the thymi of young mice suppress the proliferation of responder lymph node cells. We demonstrated that thymus-deriving CD4(+) CD25(+) T cells of old mice maintain their potential to suppress the proliferation of activated responder lymphocytes of young mice. However, their potential to inhibit the proliferation of old responder T cells is abrogated. Differences in the occurrence and activity of CD4(+) CD25(+) thymocytes between young and old animals are discussed in relation to the expression of these surface markers.     

Remote astrocytic and microglial activation modulates neuronal hyperexcitability and below-level neuropathic pain after spinal injury in rat

In this study, we evaluated whether astrocytic and microglial activation mediates below-level neuropathic pain following spinal cord injury. Male Sprague–Dawley (225–250 g) rats were given low thoracic (T13) spinal transverse hemisection and behavioral, electrophysiological and immunohistochemical methods were used to examine the development and maintenance of below-level neuropathic pain. On postoperation day 28, both hind limbs showed significantly decreased paw withdrawal thresholds and thermal latencies as well as hyperexcitability of lumbar (L4-5) spinal wide dynamic range (WDR) neurons on both sides of spinal dorsal horn compared to sham controls (* P<0.05). Intrathecal treatment with propentofylline (PPF, 10 mM) for 7 consecutive days immediately after spinal injury attenuated the development of mechanical allodynia and thermal hyperalgesia in both hind limbs in a dose-related reduction compared to vehicle treatments (* P<0.05). Intrathecal treatment with single injections of PPF at 28 days after spinal injury, attenuated the existing mechanical allodynia and thermal hyperalgesia in both hind limbs in a dose related reduction (* P<0.05). In electrophysiological studies, topical treatment of 10 mM PPF onto the spinal surface attenuated the neuronal hyperexcitability in response to mechanical stimuli. In immunohistochemical studies, astrocytes and microglia in rats with spinal hemisection showed significantly increased GFAP and OX-42 expression in both superficial and deep dorsal horns in the lumbar spinal dorsal horn compared to sham controls (* P<0.05) that was prevented in a dose-related manner by PPF. In conclusion, our present data support astrocytic and microglial activation that contributes to below-level central neuropathic pain following spinal cord injury.