Slc:Wistar outbred rats show close genetic similarity with F344 inbred rats

Although Slc:Wistar rats are used widely in biomedical research as outbred rats, close similarities in growth curves, survival rates, and immunological and biochemical phenotypes have been reported between Slc:Wistar and F344 inbred rats. We reported previously that nine genetic variations that were fixed in Slc:Wistar rats had identical genotypes in F344 rats. Here, we examined the genetic characteristics of Slc:Wistar rats using 27 simple-sequence length polymorphism (SSLP) markers and compared them with other Wistar stocks available in Japan and with some F344 strains. Among 27 SSLP loci, 23 (85%) were fixed in the Slc:Wistar rats, which was the highest among the other Wistar stocks. The 23 fixed loci shared identical genotypes with corresponding loci in F344 rats. Further, the predominant allele types in the unfixed loci had allele frequencies as high as 80%, and these alleles were identical in the F344 rats. When the nine genetic variations reported previously are added, a total of 32 (89%) out of the 36 loci examined were fixed and identical in the Slc:Wistar and F344 rat genomes. These findings indicate the low genetic variation in Slc:Wistar rats and the high genetic similarity between the Slc:Wistar and F344 inbred rats. This study demonstrates the importance of characterizing outbred rats and the need to pay ample attention to the genetic characteristics the Slc:Wistar rats for their proper use.     

Cryopreservation of spermatozoa from closed colonies, and inbred, spontaneous mutant, and transgenic strains of rats

We attempted to cryopreserve spermatozoa from closed colonies (Jcl:SD and Jcl:Wistar), and inbred (BN/Crj, F3441 DuCrj, LEW/Crj, Long-Evans and WKY/NCrj), mutant (Zitter [WTC.ZI-zi] and Tremor [TRM]), transgenic (human A-transferase [A], and green fluorescent protein [GFP]) strains of rats. Rat epididymal spermatozoa suspended in cryopreservation solution (23% egg yolk, 8% lactose monohydrate, and 0.7% Equex Stm, pH 7.4, adjusted with 10% Tris [hydroxymethy] aminomethane) were frozen and stored at -196 degrees C. After thawing at 37 degrees C, the spermatozoa were instilled into the tip of each uterine horn of the recipients. A total of five recipient females for each strain were inseminated with cryopreserved spermatozoa, and normal live offspring of all strains (Jcl:SD: 11, Jcl:Wistar: 13, BN/Crj: 9, F344/DuCrj: 28, LEW/Crj: 4, Long-Evans: 6, WKY/NCrj: 8, TRM: 24, WTC.ZI-zi: 27, A: 30 and GFP: 20) were obtained.     

A combined treatment with ethanol and 6-dimethylaminopurine is effective for the activation and further embryonic development of oocytes from Sprague-Dawley and Wistar rats

In nuclear-transferred or round spermatid-injected oocytes, artificial activation is required for further development in mammals. Although strontium chloride is widely used as the reagent for inducing oocyte activation in mice, the optimal method for oocyte activation remains controversial in rats because ovulated rat oocytes are spontaneously activated in vitro before artificial activation is applied. In our previous study, we found that cytostatic factor activity, which is indispensable for arrest at the MII stage, is potentially low in rats and that this activity differs greatly between two outbred rats (Slc: Sprague-Dawley (SD) and Crj: Wistar). Therefore, it is necessary to establish an optimal protocol for oocyte activation independent of strains. Given that comparative studies of the in vitro development of oocytes activated by different activation protocols are very limited, we compared four different protocols for oocyte activation (ethanol, ionomycin, strontium and electrical pulses) in two different SD and Wistar rats. Our results show that oocytes derived from SD rats have significantly higher cleavage and blastocyst formation than those from Wistar rats independent of activation regimes. In both types of rat, ethanol treatment provided significantly higher developmental ability at cleavage and blastocyst formation compared to the other activation protocols. However, the initial culture in a fertilization medium (high osmolarity mR1ECM) for 24 h showed a detrimental effect on the further in vitro development of parthenogenetic rat oocytes. Taken together, our results show that ethanol treatment is the optimal protocol for the activation of rat oocytes in SD and Wistar outbred rats. Our data also suggest that high-osmolarity media are inadequate for the in vitro development of parthenogenetically activated oocytes compared with fertilized oocytes.     

Comparison of characteristics between F344 and Slc:Wistar rats--Slc:Wistar rats cannot be distinguished from the F344 strain

With respect to F344/DuCrj and Slc: Wistar rats, both widely used in Japan, it was found that there is a close similarity in the changes of body weights and survival rates, and in the organ distribution and incidence of spontaneous tumors. To examine the degree of homozygosity between F344 and Slc: Wistar strains, tumor transplantation and skin grafting were performed. The bladder carcinomas that originated from F344/DuCrj rats grew subcutaneously in the other F344 strains and Slc: Wistar rats, but did not grow in the other Wistar-derived strains. The skin grafts between F344/DuCrj or F344/NSlc and Slc: Wistar rats were accepted, but those between F344/DuCrj or Slc: Wistar and the other Wistar-derived strains were rejected. These results suggest that Slc: Wistar rats cannot be distinguished genetically from the F344 strain of rats.     

Spontaneous leukemia occurring in aged Slc: Wistar rats and its transplantation into rats

Spontaneous leukemia occurred in 36% of a group of 39 aged Slc: Wistar rats, which ranged in age at death from 99 to 123 (average age: 114) weeks old. The leukemic rats showed hemolytic anemia, jaundice and leukocytosis (21,000 to 360,000/mm3). Macroscopically, they were characterized by splenomegaly and hepatomegaly. The leukemia cells were rich in basophilic cytoplasm containing eosinophilic granules. Their nuclei were oval and occasionally revealed mitotic figures. These leukemia cells were consistently transplantable into both Slc: Wistar and F 344/NSlc rats. In the transplanted cases, the latency and survival periods were prolonged in proportion to decreases in the inoculated cell dose.     

Hepatic and pancreatic glycosphingolipid phenotypes of the neurological different rat strains

Among three commonly used strains of laboratory rats, Wistar rats perform more neurological tasks better then Lewis and Sprague-Dawley (SD) rats. Liver is the main site of insulin-like growth factor (IGF) production and pancreas is the exclusive site of insulin production. Insulin stimulates neuronal development and appropriate IGF-I input is critical in brain growth. Glycosphingolipids (GSLs) are important mediators of insulin secretion and action. Therefore, this study investigated GSL phenotypes of liver and pancreas with hypothesis that they are different in three rat strains. Total GSL fractions (neutral and gangliosides) were analysed by high performance thin-layer chromatography (HPTLC). Complex gangliosides were detected by HPTLC immunostaining using cholera toxin B subunit after neuraminidase pretreatment. Wistar rats had the highest liver weight/body weight ratio and SD rats had the highest pancreas weight/body weight ratio. Ganglioside GM3 was more expressed in the liver of Wistar compared to Lewis and SD rats. SD rats contained scarce quantities of GD1a and b-series gangliosides in the liver compared to Wistar and Lewis rats. Pancreatic b-series ganglioside content was also the lowest in SD rats. This study represents differences in the hepatic and pancreatic ganglioside phenotypes of three rat strains that could influence IGF and insulin secretion and action.     

Strain Differences in Superovulatory Response, Embryo Development and Efficiency of Transgenic Rat Production

The differences between rat strains in superovulation response, in vitro and in vivo development of preimplantation embryos and overall transgenic efficiency was studied. The protocols for induction of superovulation using single injections of pregnant mare’s serum gonadotropin (PMSG) or minipumps with follicle stimulating hormone (FSH) were compared in Lewis (LEW), Wistar-Kyoto (WKY), and stroke-prone spontaneously hypertensive rats (SHRSP) or Sprague–Dawley (SD) and Wistar rats as representative inbred or outbred strains, respectively. The percentage of mated animals with positive superovulatory response was similar in all strains (60.0–100%). The mean number of ova per donor was not dependent on the kind of hormonal treatment used within each rat strain. In general, females from outbred SD and Wistar rats were more responsive to hormonal treatments than animals from inbred rat strains. In addition, SD female rats produced a significantly higher number of embryos per female in response to PMSG-treatment compared to all other strains. Between the inbred strains, SHRSP was the most effective for superovulation. In vitro development of intact zygotes to the blastocyst stage was not different between SD, Wistar and SHRSP rats. In contrast, in vitro development of WKY zygotes was significantly less efficient than in other strains. However, 2-cell stage embryos in vivo produced from SD, SD × Wistar and WKY animals showed no difference in competence to develop to blastocyst stage in vitro. The proportion of offspring developing after oviduct transfer of intact zygotes was similar in all strains (44.0–56.4%) with the exception of WKY rats (35.9%). We also compared the survival rate after injection, ability of manipulated zygotes to develop to term and overall transgenic efficiency in various rat strains. SD and SHRSP zygotes survived after microinjection better than the WKY and Lewis zygotes. No differences were found in the efficiency of transgene integration per newborn in different strains ranging from 5.7 to 16.7%. The results of this study demonstrate that different rat strains have varying responses to superovulation, sensitivity to microinjection, capability to develop in vitro until blastocyst stage or in vivo to term after transfer to foster mothers. Despite these differences all studied strains can be used for efficient transgenic rat production.     

Anti-inflammatory activity of shikonin derivatives from Arnebia hispidissima.

Arnebia hispidissima ethanolic extract, after chromatography, yielded a number of shikonin derivatives, which were identified as arnebin-5, arnebin-6, teracryl shikonin, arnebinone and acetyl shikonin. All these compounds were firstly reported from this plant species and evaluated to the anti-inflammatory activity of ethanolic extract and isolated shikonin derivatives, models with carrageenan-induced paw edema and complete Freund's adjuvant (CFA)-induced chronic arthritis in rats were conducted. The observed results indicated that pre-treatment with arnebinone significantly inhibited the carrageenan-induced paw edema and also suppressed the development of chronic arthritis induced by CFA.     

SD大鼠和Wistar大鼠实验性自身免疫性脑脊髓炎发病情况比较

目的比较Wistar大鼠和Sprague-Dawley（SD）大鼠实验性自身免疫性脑脊髓炎（EAE）发病情况。方法注射以豚鼠脊髓匀浆-完全福氏佐剂制备的完全抗原,辅以百日咳疫苗加强诱导,复制Wistar大鼠和SD大鼠EAE模型,比较两组大鼠EAE的神经症状及中枢神经不同部位病理学改变。结果Wistar大鼠组发病数、潜伏期、发病达峰时间以及神经症状最高评分分别为9/12、12.33±1.37、15.17±3.19、1.33±0.41;SD大鼠组分别为11/12、15.88±0.64、18.63±1.52、3.13±1.89;两组大鼠相比,SD大鼠EAE潜伏期延长（P〈0.01）,达峰时间相应推迟（P〈0.05）,但神经症状较Wistar大鼠严重（P〈0.05）;病理结果显示,两组大鼠CNS均以脑干病理改变最为严重,而大脑病变最轻,SD大鼠总体中枢系统炎症改变较Wistar大鼠严重（标准评分P〈0.01,血管套计数P〈0.05）。结论SD大鼠EAE与Wistar大鼠EAE比较,发病过程很相似：发病率接近,中枢炎症病理改变相仿,两者均以脑干炎症变化最严重;略有不同点是：SD大鼠EAE发病潜伏期较长（P〈0.01）,神经症状较严重（P〈0.05）,总体中枢炎症改变较为严重。故SD大鼠也是制备EAE模型的理想实验动物。     

Factors affecting production of transgenic rats by ICSI-mediated DNA transfer: effects of sonication and freeze-thawing of spermatozoa, rat strains for sperm and oocyte donors, and different constructs of exogenous DNA

Factors affecting the efficiency of producing transgenic rats by intracytoplasmic sperm injection (ICSI)-mediated DNA transfer were investigated. Epididymal spermatozoa from Sprague-Dawley (SD) rats were sonicated and/or frozen-thawed for cutting the tail and membrane disruption. The sperm heads were exposed for 1 min to different concentrations (0.02-2.5 microg/ml) of 3.0 kb enhanced green fluorescent protein (EGFP) DNA solution, and then microinjected into the denuded F1 hybrid (Donryu x LEW) rat oocytes. The optimal concentration of EGFP DNA solution was 0.1 microg/ml, as determined by the in vitro developmental competence into morulae/blastocysts of the ICSI oocytes and the EGFP expression of the resultant embryos. The efficiency of producing transgenic rat offspring (per transferred zygote) was 2.8%, 1.6%, and 3.3% in the oocytes injected with sonicated, frozen-thawed, and sonicated + frozen-thawed sperm heads, respectively. The founder transgenic rats carrying the EGFP gene transmitted their transgenes to their progeny according to the Mendelian fashion, suggesting the stable incorporation of the transgenes into the rat genomes. Four rat strains (F344, LEW, Donryu, and SD) were compared for their suitability as sperm/oocyte donors for the production of transgenic rats by ICSI with sonicated, frozen-thawed and solution of EGFP DNA-exposed sperm heads. The efficiency of producing transgenic rats in the SD strain (8.2%) was higher than that in the LEW strain (0.9%), while those in the F344 and Donryu strains (4.3%-4.4%) were intermediate. One plasmid DNA (Fyn, 5.0 kb) and two BAC DNA (BAC/Fyn, 208 kb; Svet1/IRES-Cre, 186 kb) were successfully introduced into the SD rat genomes via ICSI, with the producing efficiencies of 2.8%, 0.9%, and 2.4%, respectively.     

Antiinflammatory effect of a protein kinase C inhibitor (K-252a) on the development of the dextran-induced paw edema in the rat (preliminary results).

The effect of a metabolite of Nocardiopsis sp. as a protein kinase C inhibitor from microbial origin was investigated on the onset and development of dextran-induced paw edema in the rat. It was published that this compound (K-252a) interferes with histamine release from mast cells, while dextran-induced paw and nose edema are induced by vasoactive agents, like histamine etc., released from the disrupted mast cells. The antiinflammatory effect of the K-252a is effectuated by the inhibition of protein kinase C. Groups of male Wistar rats with 180-200 g b.w. were used; each group consisted of 10-10 rats. The following groups were consisted: rats given orally DMSO (control), rats given 1 mg/kg, or 3 mg/kg b.w. of K-252a dissolved in DMSO and given p.o. one hour before dextran injection. Dextran (BDH Chem. LTD, molW: 200.000, England) was injected intraperitoneally in 10% solution, in a dose of one ml/100 g b.w. Volume of the hind leg was measured by a mercury plethysmometer. Time-sequence of the edema was followed. Increase in volume of hind leg paw was related to its 0-min volume in %. Results were analyzed by the Kruskal-Wallis-test. Edema of the legs and noses appeared in each of the control rats in one hour. The 1 mg/kg dose of K-252a retarded the appearance of the edema by 1 hour, the 3 mg/kg dose, however, prevented its onset for 4 hours.(ABSTRACT TRUNCATED AT 250 WORDS)     

A mutant rat strain deficient in induction of a phenobarbital-inducible form of cytochrome P-450 in liver microsomes

Two phenobarbital-inducible forms of cytochrome P-450, P-450(PB-1), and P-450(PB-4), were purified from the liver microsomes of phenobarbital-treated rats and identified with P-450b and P-450e, respectively. It was found, however, that the content of P-450(PB-4) in the liver microsomes of a strain of SD rat, Qdj:SD, was very low even after phenobarbital-induction. The levels of the mRNAs for P-450(PB-1) and P-450(PB-4) were separately determined using Northern blot hybridization with specific oligonucleotide probes. It was found that the level of P-450(PB-4) mRNA in the livers of phenobarbital-treated Qdj:SD rats was much lower than that of phenobarbital-treated Slc:SD rats. Slc:SD rats are widely used in Japanese laboratories. Genetic analysis using the crossbred animals between Qdj:SD and Slc:SD rats showed that the low expression of P-450(PB-4) in Qdj:SD rats is a recessive trait and is caused by a single gene mutation. However, no difference in the 5' flanking region in P-450(PB-4) gene was found between Qdj:SD rats and Slc:SD rats.     

Anti-inflammatory and analgesic activity of ononitol monohydrate isolated from Cassia tora L. in animal models

Ononitol monohydrate (OM) was isolated from Cassia tora L. leaves. The anti-inflammatory and analgesic activities of OM have been examined in male Wistar rats and mice. The efficacy of OM against inflammation was studied by using carrageenan-induced paw oedema, croton oil-induced ear oedema, acetic acid-induced vascular permeability, cotton pellet-induced granuloma and adjuvant-induced arthritis. The analgesic activity of OM was assessed using the acetic acid-induced abdominal constriction response, formalin-induced paw licking response and the hot-plate test. In acute type inflammation models, maximum inhibitions of 50.69 and 61.06% (P < .05) were noted with 20 mg/kg of OM in carrageenan-induced hind paw oedema and croton oil-induced ear oedema, respectively. Treatment of OM (20 mg/kg) meaningfully (P < .05) reduced the granuloma tissue formation by cotton pellet study at a rate of 36.25%. OM (20 mg/kg) inhibited 53.64% of paw thickness in adjuvant-induced arthritis model. OM has also been produced significant (P < .05) analgesic activity in acetic acid-induced abdominal constriction response, formalin-induced paw licking response and in hot-plate test suggesting its peripheral and central analgesic potential. The outcomes of the present study proposed that OM influenced on the anti-inflammatory and analgesic activities.     

Inconsistent susceptibility to autoimmunity in inbred LEW rats is due to genetic crossbreeding involving segregation of the arthritis-regulating gene Ncf1

We recently identified a single-nucleotide polymorphism in the Ncf1 gene, a component of the NADPH oxidase complex, to be the cause of one of the strongest identified loci for arthritis severity in rats. This polymorphism was found to be naturally occurring in a collection of inbred rat strains as well as in wild rats. Among the inbred strains we found that different LEW substrains (LEW/Ztm and LEW/Mol), originating from different breeders, showed an allelic discrepancy in Ncf1, suggesting an impact on arthritis susceptibility between these substrains. In fact, the LEW/Mol strain was completely resistant to pristane-induced arthritis, in contrast to the LEW/Ztm strain, which was susceptible. Moreover, the LEW/Mol strain had higher production of radical oxygen species in peripheral blood leukocytes, a phenomenon most likely regulated by the polymorphisms in the Ncf1 gene. However, the phenotypic difference between LEW/Mol and LEW/Ztm is most likely a combination of several genes, of which Ncf1 is suggested to be the major regulating gene. This has also been confirmed by previous linkage analyses involving the LEW/Ztm strain which shows that a QTL on chromosome 12, most likely caused by polymorphism of Ncf1, is the major regulatory gene but that other loci are contributing. That more genes are likely to contribute was shown by a complete genome comparison of the LEW/Ztm and the LEW/Mol rat strains that uncovered an introduction of approximately 37% non-LEW genome into the LEW/Mol strain, which probably was caused by past crossbreeding. Therefore, the LEW/Mol should be regarded as a recombinant inbred strain.     

Upregulation of Slc39a10 gene expression in response to thyroid hormones in intestine and kidney

A novel zinc transporter has been purified and cloned from rat renal brush border membrane. This transporter was designated as Zip10 encoded by Slc39a10 gene and characterized as zinc importer. Present study documents the impact of thyroid hormones on the expression of Zip10 encoded by Slc39a10 gene in rat model of hypo and hyperthyroidism. Serum T(3) and T(4) levels were reduced significantly in hypothyroid rats whereas these levels were significantly elevated in hyperthyroid rats as compared to euthyroid rats thereby confirming the validity of the model. Kinetic studies revealed a significant increase in the initial and equilibrium uptake of Zn(++) in both intestinal and renal BBMV of hyperthyroid rats in comparison to hypothyroid and euthyroid rats. By RT-PCR, Slc39a10 mRNA expression was found to be significantly decreased in hypothyroid and increased in hyperthyroid as compared to euthyroid rats. These findings are in conformity with the immunofluorescence studies that revealed markedly higher fluorescence intensity at periphery of both intestinal and renal cells isolated from hyperthyroid rats as compared to hypothyroid and euthyroid rats. Higher expression of Zip10 protein in hyperthyroid group was also confirmed by western blot. These findings suggest that expression of zinc transporter protein Zip10 (Slc39a10) in intestine and kidney is positively regulated by thyroid hormones.     

Exogenous tumour necrosis factor α induces suppression of autoimmune arthritis

Introduction  

Our previous studies showed that arthritic Lewis (LEW) rats produced the highest levels of tumour necrosis factor (TNF)α in the recovery phase of adjuvant arthritis (AA), suggesting a correlation between high TNFα levels and reduced severity of arthritis. To further explore this correlation, we compared the TNFα secretion profile of the AA-resistant Wistar Kyoto (WKY) rats with that of LEW rats, determined the effect of exogenous TNFα on the course of AA in LEW rats, and examined various mechanisms involved in TNFα-induced disease modulation.     

Optimization of pulsed electromagnetic field therapy for management of arthritis in rats

Studies were undertaken to find out the effects of low frequency pulsed electromagnetic field (PEMF) in adjuvant induced arthritis (AIA) in rats, a widely used model for screening potential therapies for rheumatoid arthritis (RA). AIA was induced by an intradermal injection of a suspension of heat killed Mycobacterium tuberculosis (500 mug/0.1 ml) into the right hind paw of male Wistar rats. This resulted in swelling, loss of body weight, increase in paw volume as well as the activity of lysosomal enzymes viz., acid phosphatase, cathepsin D, and beta-glucuronidase and significant radiological and histological changes. PEMF therapy for arthritis involved optimization of three significant factors, viz., frequency, intensity, and duration; and the waveform used is sinusoidal. The use of factorial design in lieu of conventional method resulted in the development of an ideal combination of these factors. PEMF was applied using a Fransleau-Braunbeck coil system. A magnetic field of 5 Hz x 4 muT x 90 min was found to be optimal in lowering the paw edema volume and decreasing the activity of lysosomal enzymes. Soft tissue swelling was shown to be reduced as evidenced by radiology. Histological studies confirmed reduction in inflammatory cells infiltration, hyperplasia, and hypertrophy of cells lining synovial membrane. PEMF was also shown to have a membrane stabilizing action by significantly inhibiting the rate of release of beta-glucuronidase from lysosomal rich and sub-cellular fractions. The results indicated that PEMF could be developed as a potential therapy in the treatment of arthritis in humans.     

Effects of an anesthetic mixture of medetomidine,midazolam, and butorphanol in rats—strain difference and antagonism by atipamezole

An anesthetic mixture of medetomidine (MED), midazolam (MID), and butorphanol (BUT) has been used in laboratory animals. We previously reported that this anesthetic mixture produced closely similar anesthetic effects in BALB/c and C57BL/6J strains. We also demonstrated the efficacy of atipamezole (ATI), an antagonist of MED that produced quick recovery from anesthesia in mice. Anesthetics have various anesthetic effects among animal strains. However, the differences in the effects of anesthetic mixtures in rats are unclear. In the present study, we first examined effects of the abovementioned anesthetic mixture using three different rat strains: Wistar (WST), Sprague-Dawley (SD), and Fischer 344 (F344). Second, we examined how different dosages and optimum injection timing of ATI affected recovery from anesthesia in rats. We used the anesthetic score to measure anesthetic duration and a pulse oximeter to monitor vital signs. We found no significant differences in anesthetic duration among the three different strains. However, recovery from anesthesia in the SD strain took significantly longer than in the other strains. The antagonistic effects of ATI (0.15 mg/kg and 0.75 mg/kg) were equivalent when administered at 30 min after anesthetic mixture administration. The antagonistic effects of ATI 0.75 mg/kg were stronger than those of ATI 0.15 mg/kg at 10 min after anesthetic mixture administration. This anesthetic mixture is a useful drug that can induce similar anesthetic effects in three different strains and has an antagonist, ATI, that makes rats quickly recover from anesthesia. These results may contribute to the welfare of laboratory animals.     

Spontaneous bone marrow granulomas in rats--effect of ovariectomy on granulomas formation

Spontaneous granulomas developed frequently in the bone marrow of Slc: Wistar female rats over 19 weeks of age, whereas none did in JCL: SD and Slc: SD rats of either sex. These granulomas were composed histologically of epithelioid cells and macrophages clustered mostly in the center and lymphocytes and plasma cells located in the periphery, and they contained neither microorganisms nor foreign bodies. Ovariectomy of Slc: Wistar rats at 6 weeks of age resulted in a significant decrease in the incidence and size of bone marrow granulomas at 20 and 24 weeks of age. It is concluded that two factors, the strain of rats and female sex hormone, contribute to the pathogenesis of bone marrow granulomas--the former as a hereditary disposition and the latter as a promoter.     

<Emphasis Type="Italic">Celastrus aculeatus</Emphasis>Merr. suppresses the induction and progression of autoimmune arthritis by modulating immune response to heat-shock protein 65

Complementary and alternative medicine products are increasingly being used for the treatment of autoimmune diseases. However, the mechanisms of action of these agents are not fully defined. Using the rat adjuvant arthritis (AA) model of human rheumatoid arthritis, we determined whether the ethanol extract of Celastrus aculeatus Merr. (Celastrus), a Chinese herb, can down-modulate the severity of AA, and also examined the Celastrus-induced changes in immune responses to the disease-related antigen mycobacterial heat-shock protein 65 (Bhsp65). AA was induced in the Lewis (LEW; RT.1^l) rat by immunization subcutaneously with heat-killed M. tuberculosis H37Ra (Mtb). Celastrus was fed to LEW rats by gavage daily, beginning either before Mtb challenge (preventive regimen) or after the onset of AA (therapeutic regimen). An additional group of rats was given methotrexate for comparison. All rats were graded regularly for the signs of arthritis. In parallel, the draining lymph node cells of Celastrus-treated rats were tested for proliferative and cytokine responses, whereas their sera were tested for the inflammatory mediator nitric oxide. Celastrus feeding suppressed both the induction as well as the progression of AA, and the latter effect was comparable to that of methotrexate. Celastrus treatment induced relative deviation of the cytokine response to anti-inflammatory type and enhanced the production of anti-Bhsp65 antibodies, which are known to be protective against AA. Celastrus feeding also reduced the levels of nitric oxide. On the basis of our results, we suggest further systematic exploration of Celastrus as an adjunct therapeutic modality for rheumatoid arthritis.