Dose-Dependent Effect of Hyperbaric Oxygen Treatment on Burn-Induced Neuropathic Pain in Rats.

Hyperbaric oxygen treatment (HBOT) has been used to reduce neuropathic pain. Melatonin and opioid receptors are involved in neuropathic pain, but it is not known if HBOT works through these pathways to achieve its antinociceptive effect. We divided anesthetized rats into two treatment and three sham groups. The two treatment groups received third-degree burns on their right hind paws, one treated in a hyperbaric chamber for a week and the other for two weeks. We evaluated the mechanical paw-withdrawal threshold (MWT) and expression of melatonin receptor 1 (MT1), melatonin receptor 2 (MT2), µ (MOR) and κ (KOR) opioid receptor, brain-derived neurotrophic factor (BDNF), Substance P, and calcitonin gene-related peptide (CGRP) in cuneate nucleus, dorsal horn, and hind paw skin by immunohistochemical, immunofluorescence assays and real-time quantitative polymerase chain reaction (RT-PCR). The group receiving one-week HBOT had increased expressions of MT1, MT2, MOR and KOR and decreased expressions of BDNF, Substance P, and CGRP. Their mechanically measured pain levels returned to normal within a week and lasted three weeks. This anti-allodynia effect lasted twice as long in those treated for two weeks. Our findings suggest that increasing the duration of HBOT can reduce burn-induced mechanical allodynia for an extended period of time in rats. The upregulation of melatonin and opioid receptors observed after one week of HBOT suggests they may be partly involved in attenuation of the mechanical allodynia. Downregulation of BDNF, substance P and CGRP may have also contributed to the overall beneficial effect of HBOT.

Early Hyperbaric Oxygen Treatment Attenuates Burn-Induced Neuroinflammation by Inhibiting the Galectin-3-Dependent Toll-Like Receptor-4 Pathway in a Rat Model.

Hyperbaric oxygen (HBO) treatment has been proven to decrease neuroinflammation in rats. This study aimed to determine the potential mechanism underlying the anti-inflammatory effects of HBO treatment on burn-induced neuroinflammation in rats. Thirty-six adult male Sprague-Dawley (SD) rats were randomly assigned to the following six groups (n = 6 per group): (1) sham burn with sham HBO treatment; (2) sham burn with HBO treatment; (3) burn with one-week sham HBO treatment; (4) burn with two-week sham HBO treatment; (5) burn with one-week HBO treatment; and (6) burn with two-week HBO treatment. SD rats that received third-degree burn injury were used as a full-thickness burn injury model. Subsequently, we analyzed the expression of proteins involved in the galectin-3 (Gal-3)-dependent Toll-like receptor-4 (TLR-4) pathway through enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC) analysis, and Western blotting. A behavior test was also conducted, which revealed that HBO treatment significantly suppressed mechanical hypersensitivity in the burn with HBO treatment group compared to the burn with sham HBO treatment group (p < 0.05). ELISA results showed that tumor necrosis factor α (TNF-α) and interleukin 1 beta (IL-1ß) levels in the dorsal horn of the spinal cord and the skin significantly decreased in the burn with HBO treatment group compared with the burn with sham HBO treatment group (p < 0.05). Western blotting results demonstrated that HBO treatment significantly reduced the expression of Gal-3 and TLR-4 in the dorsal horn of the spinal cord in the burn with HBO treatment group compared with the burn with sham HBO treatment group (p < 0.05). IHC analysis showed that the expression of Gal-3, TLR-4, CD68 and CD45 in the dorsal horn of the spinal cord was significantly lower in the burn with HBO treatment group than in the burn with sham HBO treatment group (p < 0.05), and the expression of CD68 and macrophage migration inhibitory factor (MIF) in the right hind paw skin was significantly lower. The expression of vimentin and fibroblast growth factor in the right hind paw skin was significantly higher after HBO treatment (p < 0.05). This study proved that early HBO treatment relieves neuropathic pain, inhibits the Gal-3-dependent TLR-4 pathway, and suppresses microglia and macrophage activation in a rat model.

Codonopsis pilosula polysaccharide attenuates cecal ligation and puncture sepsis via circuiting regulatory T cells in mice.

BACKGROUND: Codonopsis pilosula polysaccharide (CPPS) isolated from one of the Chinese herbs is known to have a variety of immunomodulatory activities. However, it is not clear whether CPPS can exert an effect on the immune functions of regulatory T cells (Tregs). This study was carried out to investigate the effect of CPPS on the immune function of peripheral blood Tregs in sepsis induced by cecal ligation and puncture (CLP). METHODOLOGY AND PRINCIPAL FINDINGS: BALB/c mice were randomly divided into five groups: sham group, CLP group, CLP with CPPS (40, 100, and 250 mg/kg) treatment group, and they were killed on days 1, 2, 3, and 4 after CLP, respectively, with eight animals at each time point. Magnetic microbeads were used to isolate peripheral blood Tregs and CD4 T cells. Phenotypes of Tregs, such as Toll-like receptor 4 (TLR4) and Foxp3, were analyzed by flow cytometry, and coculture medium cytokines levels were determined with enzyme-linked immunosorbent assay. The levels of TLR4 and the expression of Foxp3 in the Treg from CLP group were markedly increased in comparison to the sham group. Administration of CPPS could significantly decrease the TLR4 level and inhibited the expression of Foxp3 on Tregs in sepsis mice. At the same time, proliferative activity and expression of interleukin 2 and interleukin 2Rα on CD4 T cells were restored. In contrast, anti-TLR4 antibody could block the effect of CPPS on Treg immune function. CONCLUSIONS: Codonopsis pilosula polysaccharide might suppress excessive Tregs, at least in part, via TLR4 signaling on Tregs and trigger a shift of TH2 to TH1 with activation of CD4 T cells in sepsis induced by CLP.