Gihyun Lee

Cortical astrocytes rewire somatosensory cortical circuits for peripheral neuropathic pain

Long-term treatments to ameliorate peripheral neuropathic pain that includes mechanical allodynia are limited. While glial activation and altered nociceptive transmission within the spinal cord are associated with the pathogenesis of mechanical allodynia, changes in cortical circuits also accompany peripheral nerve injury and may represent additional therapeutic targets. Dendritic spine plasticity in the S1 cortex appears within days following nerve injury; however, the underlying cellular mechanisms of this plasticity and whether it has a causal relationship to allodynia remain unsolved. Furthermore, it is not known whether glial activation occurs within the S1 cortex following injury or whether it contributes to this S1 synaptic plasticity. Using in vivo 2-photon imaging with genetic and pharmacological manipulations of murine models, we have shown that sciatic nerve ligation induces a re-emergence of immature metabotropic glutamate receptor 5 (mGluR5) signaling in S1 astroglia, which elicits spontaneous somatic Ca2+ transients, synaptogenic thrombospondin 1 (TSP-1) release, and synapse formation. This S1 astrocyte reactivation was evident only during the first week after injury and correlated with the temporal changes in S1 extracellular glutamate levels and dendritic spine turnover. Blocking the astrocytic mGluR5-signaling pathway suppressed mechanical allodynia, while activating this pathway in the absence of any peripheral injury induced long-lasting (>1 month) allodynia. We conclude that reawakened astrocytes are a key trigger for S1 circuit rewiring and that this contributes to neuropathic mechanical allodynia.

CD4+CD25+ regulatory T cell depletion modulates anxiety and depression-like behaviors in mice.

Stress has been shown to suppress immune function and increase susceptibility to inflammatory disease and psychiatric disease. CD4+CD25+ regulatory T (Treg) cells are prominent in immune regulation. This study was conducted to determine if anti-CD25 antibody (Ab) mediated depletion of Treg cells in mice susceptibility to stress-induced development of depression-like behaviors, as well as immunological and neurochemical activity. To accomplish this, an elevated plus-maze test (EPM), tail suspension test (TST), and forced swim test (FST) were used to examine depression-like behaviors upon chronic immobilization stress. Immune imbalance status was observed based on analysis of serum cytokines using a mouse cytometric bead array in conjunction with flow cytometry and changes in the levels of serotonin (5-HT) and dopamine (DA) in the brain were measured by high performance liquid chromatography (HPLC). The time spent in the open arms of the EPM decreased significantly and the immobility time in the FST increased significantly in the anti-CD25 Ab-treated group when compared with the non stressed wild-type group. In addition, interlukin-6 (IL-6), tumor necrosis factor-á (TNF-á), interlukin-2 (IL-2), interferon-gamma (IFN-γ), interlukin-4 (IL-4) and interlukin-17A (IL-17A) concentrations were significantly upregulated in the stressed anti-CD25 Ab-treated group when compared with the non stressed wild-type group. Furthermore, the non stressed anti-CD25 Ab-treated group displayed decreased 5-HT levels within the hippocampus when compared with the non stressed wild-type group. These results suggest that CD4+CD25+ Treg cell depletion modulated alterations in depressive behavior, cytokine and monoaminergic activity. Therefore, controlling CD4+CD25+ Treg cell function during stress may be a potent therapeutic strategy for the treatment of depression-like symptoms.

Neuro-protective effects of bee venom by suppression of neuroinflammatory responses in a mouse model of Parkinson's disease: Role of regulatory T cells

In the present study, we sought to determine whether bee venom (BV) promotes the survival of dopaminergic (DA) neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinsons disease (PD). Treatment with BV prevented degeneration of DA neurons in the substantia nigra (SN). This neuro-protective effect of BV was associated with microglial deactivation and reduction of CD4 T cell infiltration. Additionally, BV treatment significantly increased the proportion of CD4(+)CD25(+)Foxp3(+) Tregs in vivo and in vitro. The increased proportion of Tregs by BV treatment remained suppressive ex vivo. Interestingly, BV treatment did not prevent MPTP neurotoxicity in mice depleted of Tregs by anti-CD25 antibody injection. Therefore, our present studies suggest that modulation of peripheral immune tolerance by Treg may contribute to the neuroprotective effect of BV in the MPTP model of Parkinsons disease.

Bee Venom Mitigates Cisplatin-Induced Nephrotoxicity by Regulating CD4+CD25+Foxp3+ Regulatory T Cells in Mice

Cisplatin is used as a potent anticancer drug, but it often causes nephrotoxicity. Bee venom (BV) has been used for the treatment of various inflammatory diseases, and its renoprotective action was shown in NZB/W mice. However, little is known about whether BV has beneficial effects on cisplatin-induced nephrotoxicity and how such effects might be mediated. In the present study, the BV-injected group showed a significant increase in the population of Tregs in spleen. Although there was no significant difference in the numbers of Tregs 3 days after cisplatin injection between the BV- and PBS-injected groups, more migration of Tregs into the kidney was observed 6 hours after cisplatin administration in BV group than in PBS group. In addition, BV-injected mice showed reduced levels of serum creatinine, blood urea nitrogen, renal tissue damage, proinflammatory cytokines, and macrophage infiltration into the kidney 3 days after cisplatin administration. These renoprotective effects were abolished by the depletion of Tregs. The anticancer effect of repeated administrations of cisplatin was not affected by BV injection. These results suggest that BV has protective effects on cisplatin-induced nephrotoxicity in mice, at least in part, through the regulation of Tregs without a big influence on the antitumor effects of cisplatin.

Bee venom ameliorates ovalbumin induced allergic asthma via modulating CD4+CD25+ regulatory T cells in mice

Asthma is a potentially life-threatening inflammatory disease of the lung characterized by the presence of large numbers of CD4+ T cells. These cells produce the Th2 and Th17 cytokines that are thought to orchestrate the inflammation associated with asthma. Bee venom (BV) has traditionally been used to relieve pain and to treat chronic inflammatory diseases. Recent reports have suggested that BV might be an effective treatment for allergic diseases. However, there are still unanswered questions related to the efficacy of BV therapy in treating asthma and its therapeutic mechanism. In this study, we evaluated whether BV could inhibit asthma and whether BV inhibition of asthma could be correlated with regulatory T cells (Treg) activity. We found that BV treatment increased Treg populations and suppressed the production of Th1, Th2 and Th17-related cytokines in an in vitro culture system, including IL2, IL4, and IL17. Interestingly, production of IL10, an anti-inflammatory cytokine secreted by Tregs, was significantly augmented by BV treatment. We next evaluated the effects of BV treatment on allergic asthma in an ovalbumin (OVA)-induced mouse model of allergic asthma. Cellular profiling of the bronchoalveolar lavage (BAL) and histopathologic analysis demonstrated that peribronchial and perivascular inflammatory cell infiltrates were significantly lowered following BV treatment. BV also ameliorated airway hyperresponsiveness, a hallmark symptom of asthma. In addition, IL4 and IL13 levels in the BAL fluid were decreased in the BV treated group. Surprisingly, the beneficial effects of BV treatment on asthma were eradicated following Treg depletion by anti-CD25 antibody injection, suggesting that the major therapeutic targets of BV were Tregs. These results indicate that BV efficiently diminishes bronchial inflammation in an OVA-induced allergic asthma murine model, and that this effect might correlate with Tregs, which play an important role in maintaining immune homeostasis and suppressing the function of other T cells to limit the immune response. These results also suggest that BV has potential therapeutic value for controlling allergic asthma responses.

Phospholipase A2 inhibits cisplatin-induced acute kidney injury by modulating regulatory T cells by the CD206 mannose receptor

Previously, we found that Foxp3-expressing CD4(+) regulatory T (Treg) cells attenuate cisplatin-induced acute kidney injury in mice and that bee venom and its constituent phospholipase A2 (PLA2) are capable of modulating Treg cells. Here we tested whether PLA2 could inhibit cisplatin-induced acute kidney injury. As a result of treatment with PLA2, the population of Treg cells was significantly increased, both in vivo and in vitro. PLA2-injected mice showed reduced levels of serum creatinine, blood urea nitrogen, renal tissue damage, and pro-inflammatory cytokine production upon cisplatin administration. These renoprotective effects were abolished by depletion of Treg cells. Furthermore, PLA2 bound to CD206 mannose receptors on dendritic cells, essential for the PLA2-mediated protective effects on renal dysfunction. Interestingly, PLA2 treatment increased the secretion of IL-10 in the kidney from normal mice. Foxp3(+)IL-10(+) cells and CD11c(+)IL-10(+) cells were increased by PLA2 treatment. The anticancer effects of repeated administrations of a low dose of cisplatin were not affected by PLA2 treatment in a tumor-bearing model. Thus, PLA2 may prevent inflammatory responses in cisplatin-induced acute kidney injury by modulating Treg cells and IL-10 through the CD206 mannose receptor.

Bee Venom Phospholipase A2, a Novel Foxp3+ Regulatory T Cell Inducer, Protects Dopaminergic Neurons by Modulating Neuroinflammatory Responses in a Mouse Model of Parkinson's Disease.

Foxp3-expressing CD4+ regulatory T cells (Tregs) are vital for maintaining immune tolerance in animal models of various immune diseases. In the present study, we demonstrated that bee venom phospholipase A2 (bvPLA2) is the major BV compound capable of inducing Treg expansion and promotes the survival of dopaminergic neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson’s disease. We associated this neuroprotective effect of bvPLA2 with microglial deactivation and reduction of CD4+ T cell infiltration. Interestingly, bvPLA2 had no effect on mice depleted of Tregs by injecting anti-CD25 Ab. This finding indicated that Treg-mediated modulation of peripheral immune tolerance is strongly involved in the neuroprotective effects of bvPLA2. Furthermore, our results showed that bvPLA2 directly bound to CD206 on dendritic cells and consequently promoted the secretion of PGE2, which resulted in Treg differentiation via PGE2 (EP2) receptor signaling in Foxp3−CD4+ T cells. These observations suggest that bvPLA2-CD206-PGE2-EP2 signaling promotes immune tolerance through Treg differentiation and contributes to the prevention of various neurodegenerative diseases, including Parkinson’s disease.

Curcumin attenuates lupus nephritis upon interaction with regulatory T cells in New Zealand Black/White mice

Curcumin has been used in Asian traditional medicine for its medicinal properties. Recent studies have demonstrated that curcumin has antioxidant, anti-tumour and anti-inflammatory activities. The aim of the present study is to investigate the effects of curcumin on established lupus nephritis (LN) in New Zealand Black/White (NZB/W) F1 female mice, in particular, its interaction with regulatory T (Treg) cells. Starting at 18 weeks of age, mice were fed a standard diet or a diet containing 1 % curcumin until the end of the study. The proteinuria level and the serum levels of IgG1, IgG2a and anti-double-stranded DNA (dsDNA) IgG antibodies were measured. Additionally, IgG immune complex deposition in the glomeruli and renal inflammation were compared between curcumin-treated mice and control mice. Curcumin decreased the proteinuria level and serum levels of IgG1, IgG2a and anti-dsDNA IgG antibodies in NZB/W F1 female mice. IgG immune complex deposition in the glomeruli was reduced in curcumin-treated mice. Furthermore, renal inflammation was also decreased after curcumin treatment. Interestingly, these therapeutic effects of curcumin disappeared after Treg depletion by anti-CD25 antibody injection. Curcumin exerted a protective effect against LN in NZB/W F1 mice. We speculate that the protective effects of curcumin in LN may involve, at least in part, its interaction with Treg cells.

Bee venom-associated Th1/Th2 immunoglobulin class switching results in immune tolerance of NZB/W F1 murine lupus nephritis.

Background/Aims: Bee venom (BV) therapy has been used to treat inflammatory diseases including rheumatoid arthritis in humans and in experimental animals. This study was conducted to examine the therapeutic effect of BV on established lupus nephritis in New Zealand Black/White (NZB/W) F1 female mice. Methods: Beginning at 18 weeks of age, mice were given a subcutaneous injection of either BV (3 mg/kg BW) or an equal volume of saline once a week until the end of the study. To examine the effect of BV on CD4+CD25+Foxp3+ regulatory T cells, splenocytes from NZB/W mice (23 weeks of age) were treated with BV (1 µg/ml) or PBS in the presence of anti-CD3Ε (1 µg/ml) and anti-CD28 antibodies (4 µg/ml) for 48 h. Results: BV administration delayed the development of proteinuria to a significant extent, prevented renal inflammation, reduced tubular damage, and reduced immune deposits in the glomeruli. Interestingly, CD4+CD25+ regulatory T cells were significantly increased in vitro and in vivo after BV treatment. Conclusion: Collectively, the administration of BV that has immune modulating effects represents an applicable treatment of lupus nephritis in NZB/W F1 mice.

Bee venom phospholipase A2 suppresses allergic airway inflammation in an ovalbumin‐induced asthma model through the induction of regulatory T cells

Bee venom (BV) is one of the alternative medicines that have been widely used in the treatment of chronic inflammatory diseases. We previously demonstrated that BV induces immune tolerance by increasing the population of regulatory T cells (Tregs) in immune disorders. However, the major component and how it regulates the immune response have not been elucidated. We investigated whether bee venom phospholipase A2 (bvPLA2) exerts protective effects that are mediated via Tregs in OVA‐induced asthma model. bvPLA2 was administered by intraperitoneal injection into control and OVA‐challenged mice. The Treg population, total and differential bronchoalveolar lavage fluid (BALF) cell count, Th2 cytokines, and lung histological features were assessed. Treg depletion was used to determine the involvement of Treg migration and the reduction of asthmatic symptoms. The CD206‐dependence of bvPLA2‐treated suppression of airway inflammation was evaluated in OVA‐challenged CD206‐/‐ mice. The bvPLA2 treatment induced the Tregs and reduced the infiltration of inflammatory cells into the lung in the OVA‐challenged mice. Th2 cytokines in the bronchoalveolar lavage fluid (BALF) were reduced in bvPLA2‐treated mice. Although bvPLA2 suppressed the number of inflammatory cells after OVA challenge, these effects were not observed in Treg‐depleted mice. In addition, we investigated the involvement of CD206 in bvPLA2‐mediated immune tolerance in OVA‐induced asthma model. We observed a significant reduction in the levels of Th2 cytokines and inflammatory cells in the BALF of bvPLA2‐treated OVA‐induced mice but not in bvPLA2‐treated OVA‐induced CD206‐/‐ mice. These results demonstrated that bvPLA2 can mitigate airway inflammation by the induction of Tregs in an OVA‐induced asthma model.