The popliteal lymph node response to streptozotocin is under type 1, MHC class-I restricted, CD8(+) T-cell control

Antihypertriglyceridemia and anti-inflammatory activities of monascus-fermented dioscorea in streptozotocin-induced diabetic rats

The rice fermented by Monascus, called red mold rice (RMR), and has a long tradition in East Asia as a dietary staple. Monascus-fermented dioscorea called red mold dioscorea (RMD) contains various metabolites to perform the ability of reducing oxidative stress and anti-inflammatory response. We used Wistar rats and induced diabetes by injecting streptozotocin (STZ, 65 mg/kg i.p.). RMD was administered daily starting six weeks after disease onset. Throughout the experimental period, significantly (P < .05) lowered plasma glucose, triglyceride, cholesterol, free fatty acid and low density lipoprotein levels were observed in the RMD-treated groups. The RMD-treated diabetic rats showed higher activities of glutathione disulfide reductase, glutathione reductase, catalase and superoxide dismutase (P < .05) in the pancreas compared with the diabetic control rats. RMD also inhibited diabetes-induced elevation in the levels of interleukin (IL)-1β, IL-6, interferon-γ and tumor necrosis factor-α. Pancreatic β-cells damaged by STZ in the RMD supplemented groups were ameliorated. The results of this study clearly demonstrated that RMD possesses several treatment-oriented properties, including the control of hyperglycemia, antioxidant effects, pancreatic β-cell protection and anti-inflammatory effects. Considering these observations, it appears that RMD may be a useful supplement to delay the development of diabetes and its complications.

Popliteal lymph node assay: facts and perspectives

The popliteal lymph node assay (PLNA) derives from the hypothesis that some supposedly immune-mediated adverse effects induced by certain pharmaceuticals involve a mechanism resembling a graft-versus-host reaction. The injection of many but not all of these compounds into the footpad of mice or rats produces an increase in the weight and/or cellularity of the popliteal lymph node in the treated limb (direct PLNA). Some of the compounds known to cause these adverse effects in humans, however, failed to induce a positive PLNA response, leading to refinements of the technique to include pretreatment with enzyme inducers, depletion of CD4(+) T cells or additional endpoints such as histological examination, lymphocyte subset analysis and cytokine fingerprinting. Alternative approaches have been used to improve further the predictability of the assay. In the secondary PLNA, the test compound is injected twice in order to illicit a greater secondary response, thus suggesting a memory-specific T cell response. In the adoptive PLNA, popliteal lymph node cells from treated mice are injected into the footpad of naive mice; a marked response to a subsequent footpad challenge demonstrates the involvement of T cells. Finally, the reporter antigens TNP-Ficoll and TNP-ovalbumin are used to differentiate compounds that induce responses involving neo-antigen help or co-stimulatory signals (modified PLNA). The PLNA is increasingly considered as a tool for detection of the potential to induce both sensitization and autoimmune reactions. A major current limitation is validation. A small inter-laboratory validation study of the direct PLNA found consistent results. No such study has been performed using an alternative protocol. Other issues include selection of the optimal protocol for an improved prediction of sensitization vs autoimmunity, and the elimination of false-positive responses due to primary irritation. Finally, a better understanding of underlying mechanisms is essential to determine the most relevant endpoints. The confusion resulting from use of the PLNA to predict autoimmune-like reactions as well as sensitization should be clarified. Interestingly, most drugs that were positive in the direct PLNA are also known to cause drug hypersensitivity syndrome in treated patients. This observation is expected to open new avenues of research.

Anti-arthritic effect and subacute toxicological evaluation of Baccharis genistelloides aqueous extract

This work studies the potential subacute toxicological effects of the aqueous extract of Baccharis genistelloides (AEBg) and demonstrates a new anti-arthritic therapeutic effect. The treatment of the collagen-induced arthritis (CIA) group with 4.2 mg/kg AEBg induced an important decrease (75%) in CIA severity in all animals, while the 42 mg/kg dose treated only 50% of animals. After AEBg treatment, no significant differences were observed in body weight, aspect, color and relative weight of liver, kidneys, thymus or lungs between CIA groups. CIA and healthy AEBg groups treated with both doses did not show genotoxic effects to liver and kidney cells by the Comet assay, compared to its own control group. The augmented AST in the CIA group, compared to healthy control one was regularized by the AEBg treatment with 4.2 mg/kg but not with 42 mg/kg. No other significant difference was found on serum biochemical parameters, as well as on spontaneous or stimulated lymphocyte proliferation between CIA groups. The treatment of healthy animals with AEBg 4.2 mg/kg did not change the aspect, color or relative weight of kidneys, liver or lungs but reduced the body weight, the thymus and popliteal lymph node (PLN) relative weight and serum glucose and triglyceride levels. Concluding, our results indicate an anti-arthritic effects of AEBg without liver and kidney subacute toxicity and hypoglycemic and hypotriglyceridemic actions on healthy animals.

Popliteal lymph node responses to acetone and ethanol differ from those induced by streptozotocin

The popliteal lymph node (PLN) assay was proposed to detect the potential of immunotoxicants for inducing systemic autoimmune-like reactions, but also xenobiotics that are sensitizing or exert immunostimulatory properties. Results on over 100 chemicals, mostly pharmaceuticals, are available with the PLN assay and show many correlations between rodent data and the clinical experience. A major issue is that the mechanisms involved have not been fully elucidated. In order to provide mechanistic clues to improve the predictability of the PLN assay, the effects of streptozotocin (STZ) were compared to those of ethanol and acetone in normal C57Bl/6 mice as well as mice depleted in CD4+ or CD8+ T-cells by treatment with specific monoclonal antibodies. STZ, ethanol and acetone gave similar positive responses in normal mice. Neither CD4+ nor CD8+ T-cell depletion influenced the PLN responses to ethanol or acetone, whereas CD8+ in contrast to CD4+ T-cell depletion abolished the response to STZ. There was an increase in the production of IL-6 and IFN-gamma mRNAs measured by RT-PCR in STZ-, but not in ethanol- or acetone-treated normal mice. The production of TNFalpha, IL-1alpha, IL-1beta, IL-2R and IL-12 mRNAs was increased whatever the treatment, but increases were 2- to 3-fold greater after STZ than ethanol or acetone. These results suggest that PLN responses to primary irritants such as ethanol and acetone essentially reflect non-specific inflammation, whereas PLN responses to an autoimmunogenic compound such as STZ involve CD8+ T lymphocytes and the production of IFN-gamma and IL-6. These findings may prove useful to improve the predictability of the PLN assay.

Tritiated thymidine incorporation does not enhance sensitivity of the popliteal lymph node assay

The popliteal lymph node (PLN) assay has been proposed as a tool to predict drugs and chemicals with the potential to induce systemic autoimmune reactions in man. In this assay, weight and cellularity indices typically are the measured endpoints. The present study was conducted to test whether incorporation of tritiated thymidine could improve sensitivity of the PLN assay. Male and female Balb/c mice were injected with 20 microCi of [3H]-methyl-thymidine intravenously 7 days after receiving 0.5, 1 or 2 mg of diphenylhydantoin, streptozotocin, sulfamethoxazole, ofloxacin, phenobarbital, or metformin intradermally. Results obtained with incorporation of tritiated thymidine were compared to weight indices. No consistent or marked differences in these endpoints were noted whatever the compound used. This study shows that incorporation of tritiated thymidine does not improve sensitivity of the PLN assay.

Immunomodulatory and anti-inflammatory effects of Kalanchoe brasiliensis

The immunomodulatory effect of juice obtained from leaves of Kalanchoe brasiliensis (Kb) on zymosan-induced inflammation was investigated. C57B110 mice received a subcutaneous injection of 150 microg zymosan in the footpad. After 7 days, there was an increase in footpad thickness from 176 +/- 4 to 236 +/- 9 x 10(-2) mm and in blood flow in the footpad area, monitored by 99mTc, from 98 +/- 4 to 694 +/- 59 counts per minute (cpm). Zymosan induced a severe infiltration of leukocytes into the articular tissues and a 13-fold increase in the adjacent popliteal lymph node (PLN) weight. Beginning 2 days after the injection, mice were treated daily for 5 days with different concentrations of lyophilised Kb juice dissolved in water. Treatment with 480 mg/kg/day reduced footpad thickness to 193 +/- 5 x 10(-2) mm, leukocyte infiltration and blood flow to 150 +/- 18 cpm in the footpad area. PLN weight in zymosan-injected mice decreased from 6.5 +/- 0.5 to 1.5 +/- 0.4 mg, similarly to the decrease after treatment with indomethacin (3 mg/kg/day). Flow cytometric analysis of lymph node cells showed an important reduction in B cell number in Kb-treated mice. Treatment over a period of 10 days was also effective at reducing zymosan-induced inflammation, even when started 7 days after injection. These data suggest anti-inflammatory and immunosuppressive effects of K. brasiliensis that may account for its popularity in folk medicine against rheumatic diseases.

Application of the popliteal lymph node assay in immunotoxicity testing: complementation of the direct popliteal lymph node assay with flow cytometric analyses

The popliteal lymph node assay (PLNA) has been proposed to measure the immunosensitizing potential of chemicals. The direct PLNA detects an immunomodulating effect but does not give insight into the mode of action of the chemical under test. Modifications of this test have been proposed, but they are difficult to perform in routine toxicity testing and require many animals. In the present investigation the direct PLNA was extended with the flow cytometric determinations of: (a) lymphoblasts; (b) the phenotyping of lymphoid subpopulations; (c) the determination of expression of proliferation/activation markers CD25, CD69 and CD62L/CD44 and (d) the analysis of intracellular cytokines interferon gamma, interleukin 2 and interleukin 4. Streptozotocin, hydrazine, HgCl2 and trinitrobenzene sulfonic acid were used as model chemicals. The different mode of action of these substances was well documented by the techniques applied. As the proposed flow cytometric methods can easily be performed and do not require additional test animals this complementation of the direct PLNA seems a promising approach in immunotoxicity testing.

Granulocyte macrophage-colony stimulating factor (GM-CSF) recruits immune cells to the pancreas and delays STZ-induced diabetes

Granulocyte macrophage-colony stimulating factor (GM-CSF) is one of the most widely used growth factors for enhancing immune responses and is known to recruit and activate antigen-presenting cells (APCs). This study hypothesized that overexpression of this cytokine within the pancreatic beta-cells would recruit, expand, and activate APCs. The question was whether this would lead to tolerance or autoimmunity to pancreatic antigens. This possibility was tested by preparing transgenic mice (ins-GM-CSF) whose islets expressed murine GM-CSF. By 6-8 weeks of age, these mice developed a profound mononuclear cell infiltration that often overwhelmed the exocrine pancreas, although no changes in enzyme or hormone function were apparent. The majority of the mononuclear infiltrate within the pancreas was identified as F4/80+ macrophages. Transgenic ins-GM-CSF mice had splenomegaly due to a massive increase in the macrophage population. Additionally, mononuclear cells were found within the livers of transgenic mice, with F4/80+ cells also identified within the infiltrate, indicating that GM-CSF-activated mononuclear cells circulated to organs other than the pancreas. To assess the disease potential, this study tested whether macrophage recruitment to the pancreas might accelerate or protect the islets from diabetes. It was found that the induction of diabetes by low-dose streptozotocin (STZ) was delayed and reduced within ins-GM-CSF transgenic mice, in comparison with negative littermates. Together, these data highlight the role of GM-CSF in recruiting APCs such as macrophages. Advanced cellular infiltration does not overtly harm, and may even protect, pancreatic function, as seen with the delay in chemically induced diabetes.

Positive responses to imipramine in the popliteal lymph node assay are due to primary irritation

The popliteal lymph node (PLN) assay has long been proposed as a tool to detect immunotoxicants with the potential to induce systemic autoimmunity. A major problem hampering the further validation of this assay is the need to rule out irritants that cause false-positive PLN responses. The anti-depressant, imipramine, has not been reported to induce systemic autoimmune reactions in treated patients, but has been repeatedly found positive in the PLN assay, suggesting that this is a false-positive response. To test this hypothesis, the effects of imipramine were compared to those of 50% ethanol in C57B1/6 mice. Footpad edema was evidenced in the few days after injection of both ethanol and imipramine. T-cell depletion using monoclonal antibodies against either CD4+ or CD8+ T-lymphocytes prior to the PLN assay did not influence the responses to either ethanol or imipramine. Cytokine (TNFalpha, IL-1alpha, IL-1beta, IL-2R, IL-6, IL-12 and IFN-gamma) fingerprinting of the PLNs after injection of ethanol and imipramine evidenced the same pattern of responses. These results indicate a closely similar pattern of responses following the footpad injection of either imipramine or ethanol. The conclusion can be drawn that imipramine induces positive responses in the PLN assay via primary (nonspecific) irritation.