Topical application of Pseudolaric acid B improve DNFB-induced contact hypersensitivity via regulating the balance of Th1/Th17/Treg cell subsets

Pseudolaric acid B ameliorates synovial inflammation and vessel formation by stabilizing PPARγ to inhibit NF-κB signalling pathway

Synovial macrophage polarization and inflammation are essential for osteoarthritis (OA) development, yet the molecular mechanisms and regulation responsible for the pathogenesis are still poorly understood. Here, we report that pseudolaric acid B (PAB) attenuated articular cartilage degeneration and synovitis during OA. PAB, a diterpene acid, specifically inhibited NF-κB signalling and reduced the production of pro-inflammatory cytokines, which further decreased M1 polarization and vessel formation. We further provide in vivo and in vitro evidences that PAB suppressed NF-κB signalling by stabilizing PPARγ. Using PPARγ antagonist could abolish anti-inflammatory effect of PAB and rescue the activation of NF-κB signalling during OA. Our findings identify a previously unrecognized role of PAB in the regulation of OA and provide mechanisms by which PAB regulates NF-κB signalling through PPARγ, which further suggest targeting synovial inflammation or inhibiting vessel formation at early stage could be an effective preventive strategy for OA.

B-cell-specific-peroxisome proliferator-activated receptor γ deficiency augments contact hypersensitivity with impaired regulatory B cells

Nuclear receptor peroxisome proliferator-activated receptor γ (PPAR-γ) activation can prevent immunoinflammatory disorders and diabetes. B cells play protective roles during inflammation as well. However, the roles of endogenous PPAR-γ in the regulatory properties of B cells to relieve inflammation remain unknown. Here, we developed B-cell-specific PPAR-γ knockout (B-PPAR-γ^-/- ) mice and found that the conditional deletion of PPAR-γ in B cells resulted in exaggerated contact hypersensitivity (CHS). Meanwhile, interferon-γ (IFN-γ) of CD4⁺ CD8⁺ T cells was up-regulated in B-PPAR-γ^-/- mice in CHS. This showed that the regulatory function of B cells in B-PPAR-γ^-/- mice declined in vivo. Whereas splenic CD5⁺ CD1d^hi regulatory B-cell numbers and peripheral regulatory T-cell numbers were not changed in naive B-PPAR-γ^-/- mice. Loss of PPAR-γ in B cells also did not affect either CD86 or FasL expression in splenic CD5⁺ CD1d^hi regulatory B cells after activation. Notably, interleukin-10 (IL-10) production in CD5⁺ CD1d^hi regulatory B cells reduced in B-PPAR-γ-deficient mice. In addition, functional IL-10-producing CD5⁺ CD1d^hi regulatory B cells decreased in B-PPAR-γ^-/- mice in the CHS model. These findings were in accordance with augmented CHS. The current work indicated the involvement of endogenous PPAR-γ in the regulatory function of B cells by disturbing the expansion of IL-10-positive regulatory B cells.

Dihydroartemisinin derivative DC32 attenuates collagen-induced arthritis in mice by restoring the Treg/Th17 balance and inhibiting synovitis through down-regulation of IL-6

Imbalance of Treg/Th17 and chronic synovitis characterized by the recruitment and infiltration of inflammatory cells are the typical features of rheumatoid arthritis (RA). IL-6 promotes the differentiation and function of Th17 cells, which contributes to the imbalance of Treg/Th17 and aggravates lymphocytic infiltration in joints. DC32, a dihydroartemisinin derivative, was found to have anti-inflammatory and immunosuppressive activities in previous study. The aim of this study is to evaluate the effects and mechanisms of DC32 in immunodeficiency and inflammatory infiltration of RA. In vivo, the antirheumatic effect of DC32 was evaluated in a collagen-induced arthritis (CIA) mouse model in DBA/1 mice. The percentages of Treg and Th17 and transcription of IL-6 in the spleen were assayed. In vitro, a coculture system of ConA-activated lymphocytes and fibroblast-like synoviocytes (FLSs) from rat with adjuvant arthritis (AA) was established. The effects and mechanisms of DC32 on synovitis were investigated. It was shown that DC32 inhibited footpad swelling and lymphocytic infiltration in mice with CIA and significantly restored the Treg/Th17 balance by reducing the transcription of IL-6 in splenocytes. DC32 significantly inhibited the lymphocyte-induced invasion and migration of FLSs by decreasing the secretion of MMPs (MMP-2, MMP-3) in vitro. DC32 also reduced the transcription of chemokines (CXCL12, CX3CL1) and IL-6 in FLSs, as well as IL-6 levels in the supernatant. These results demonstrated that DC32 may attenuate RA by restoring Treg/Th17 balance and inhibiting lymphocytic infiltration through downregulation of the expression and transcription of IL-6. This study supports the potential of DC32 to down-regulate IL-6 for the treatment of RA and other related autoimmune diseases.

Pseudolaric acid B attenuates atopic dermatitis-like skin lesions by inhibiting interleukin-17-induced inflammation

Pseudolaric acid B (PB), isolated from the extract of the root bark of Pseudolarix kaempferi Gordon, has been used as a traditional remedy for the treatment of skin diseases. However, the information of PB on atopic dermatitis (AD) remains largely unknown. In the present study, oral administration with PB improved the severity scores of AD-like skin lesions dose-dependently in NC/Nga mice through reducing serum IgE, pro-inflammatory cytokines, and the infiltration of inflammatory cells. In addition, PB significantly attenuated the levels of IL-17 and IL-22, and the proportion of Th17 cells in NC/Nga mice, as well as decreased IL-17-induced inflammation in RAW264.7 cells. Moreover, PB inhibited the phosphorylation of IκBα and miR-155 expression both in NC/Nga mice and in IL-17-stimulated RAW264.7 cells, which could be reversed by GW9662, a specific antagonist for PPARγ. The incorporation of GW9662 reversed the inhibitory effect of PB on the RORγ-mediated activation of the Il17 promoter. Transfection with PPARγ luciferase reporter gene further demonstrated the enhancement of PB on PPARγ transactivation. These findings indicate that PB could ameliorate AD-like skin lesions by inhibiting IL-17-induced inflammation in a PPARγ-dependent manner, which would provide experimental evidence of PB for the therapeutic potential on AD and other inflammatory skin diseases.

A Systematic Review of the Immune-Regulating and Anticancer Activities of Pseudolaric Acid B

Cortex pseudolaricis, the root bark of Pseudolarix kaempferi Gord, has been used to treat tinea and other skin diseases for the antimicrobial activities in Traditional Chinese Medicine (TCM). Pseudolaric acid B (PAB) has been identified as the major component responsible for the action of C. pseudolaricis. Recently, PAB has been demonstrated to be used as novel treatments for cancer, immune disorders, inflammatory diseases, and immunosuppression. However, the mechanisms through which PAB exerts its properties are not understood well, and little attention in the literature has been given to review its pharmacological activities before. In this review, we performed a systematic summary of the literature with respect to the anticancer, immunosuppressive and anti-inflammatory properties of PAB and its derivatives. Currently available data suggest that PAB is a promising immunosuppressive and anti-inflammatory agent candidate and should be explored further in cancer treatment and prevention.

Study on the therapeutic mechanisms of pseudolaric acid in mice with allergic contact dermatitis

OBJECTIVE

To study the therapeutic mechanisms of pseudolaric acid on allergic contact dermatitis in mice.

METHODS

A total of 50 BALB/C mice were selected and randomly divided into control group, model group, and treatment A, B, C groups with 10 rats in each group. ACD model was established in model group, and treatment A, B, C groups but not in control group. Model group received no treatment, but treatment A, B, C groups were treated with external application of the concentration of 0.1%, 0.2% and 0.4% of the pseudolaric acid for the lesions of ear skin. And the weight gain and the swelling degree of the mice' ear were recorded, weight of thymus and spleen were measured. Spleen suspension was prepared to test T lymphocyte and B lymphocyte levels of mice in five groups. Changes in serum IFN-γ, IL-4 and IL-10 levels were tested through the enzyme linked immunosorbent assay (ELISA).

RESULTS

The weight gain of mice in model group were significant lower than those of mice in the control group and the treatment A, B, C groups (P < 0.05). Weight gain of mice in treatment A, B groups were significant lower than that of control group (P < 0.05), but the difference in weight gain between treatment C group and control group showed no significant difference (P > 0.05). The swelling degree and the weight of mice ears in model group were significant higher than those of mice in control group and treatment A, B, C groups (P < 0.05). Swelling degree and the weight of mice ears of treatment A, B, C groups were obviously higher than that of control group (P < 0.05). The swelling degree and weight of mice' ears in treatment A, B, C groups were decreased with the increase of the drug dosage, but comparison between A, B and C group showed statistically differences (P < 0.05). The thymus and spleen index of mice in model group were significant higher than those of the other four groups (P < 0.05), among the four groups, thymus and spleen index of treatment A and B group were higher than control group and treatment C group (P < 0.05). The stimulation index of T and B cells of mice in model group was significantly higher than the rest four groups (P < 0.05). The serum IFN-γ level of mice in control group and treatment A, B and C group was obviously lower than that of mice in model group (P < 0.05). The serum IFN-γ level of mice in treatment A, B and C group were decreased with the increasing of the drug dosage, and the level of C group was obviously lower than that of A and B group (P < 0.05).

CONCLUSION

The pseudolaric acid has anti-inflammation and immune adjustment the effects showing a remarkable therapeutic effects for the ACD mice.

A novel Pseudolaric acid B derivative, Hexahydropseudolaric acid B, exterts an immunomodulatory effect in vitro/in vivo evaluation

Identification of immunosuppressants from natural sources has a proven track record in immune mediated disorders. Pseudolaric acid B is a diterpenoid isolated from the roots of Pseudolarix amabilis, possessing potent immunomodulatory effect. However, the cytotoxicity limits its future clinical application. The purpose of this study was to investigate the immunosuppressive activity of Hexahydropseudolaric acid B, a Pseudolaric acid B derivative, on T cell-mediated immune response both in vitro and in vivo, and investigated its immunomodulatory effect to develop a more ascendant immunosuppressive agent. The results showed that Hexahydropseudolaric acid B could exert more preferable immunosuppressive activity and lower cytotoxicity than Pseudolaric acid B. Hexahydropseudolaric acid B significantly inhibited T cell proliferation activated by mitogen and alloantigen without obvious cytotoxicity in vitro. Furthermore, Hexahydropseudolaric acid B could ameliorate ear swelling in a mouse model of 2,4-dinitrofluorobenzene-induced delayed-type hypersensitivity in vivo. Mechanistic study revealed that Hexahydropseudolaric acid B could enhance regulatory T cells via promoting Foxp3 expression and TGF-β level, accompanied by attenuating Akt activation, blocking p38MAPK/MK2-HSP27 signal cascades, and up-regulating PPAR-γ expression. Taken together, these results suggest that Hexahydropseudolaric acid B exerts more preferable immunosuppressive activity than its precursor Pseudolaric acid B by affecting multiple targets, which support the need for continued efforts to characterize the efficacy of HPAB as a promising and safe candidate to treat immune-related diseases.

Pseudolaric acid B inhibits T-cell mediated immune response in vivo via p38MAPK signal cascades and PPARγ activation

AIMS

Pseudolaric acid B (PAB) has been prescribed for its potent immunomodulatory effect. However, the detail of mechanism remains to be demonstrated. The purpose of this study is to further clarify the mechanism of PAB on T-cell mediated immune response in vivo.

MAIN METHODS

Investigations were carried to ascertain the pharmacological effect of PAB in a delayed-type hypersensitivity (DTH) mouse model of T-cell mediated immune response. Histological assessment was examined by hematoxylin and eosin staining. Affymetrix GeneChip® Mouse Genome 430 2.0 arrays were employed to evaluate the expression profile of PAB. Western blot was performed to detect p38MAPK signal cascades, including p38MAPK, ATF-2, MK2, and HSP27. Finally, TNF-α level was analyzed by ELISA, and Jurkat T cells were treated with PAB to determine its role on PPARγ activation using a reporter gene assay.

KEY FINDINGS

The results showed that PAB (5, 10, and 20mg/kg) could lead to a marked improvement for ear swelling and inflammatory infiltrate in DTH mice dose-dependently. According to the associated biological pathways from microarray analysis, PAB resulted in the restoration of abnormal immune-related gene expression linked to MAPK and PPAR signaling pathways. Moreover, PAB inhibited the activation of p38MAPK, ATF-2, MK2, and HSP27 significantly, as well as the production of TNF-α, which was reversed by GW9662, a specific antagonist for PPARγ. In addition, treatment with PAB also increased the transcriptional activity of PPARγ in a dose-dependent manner.

SIGNIFICANCE

These results provide us with novel insights into pharmacological action of PAB as a potential immunomodulator for the treatment of immune-related diseases.