Assessing carrageenan-induced locomotor activity impairment in rats: comparison with evoked endpoint of acute inflammatory pain

BACKGROUND

Most animal models currently used to evaluate antinociceptive efficacy of analgesics rely on the assessment of evoked pain behaviours as primary endpoints.

METHODS

Here, we have developed and characterized the carrageenan-induced locomotor activity impairment (CLAIM) model to objectively assess non-evoked inflammatory pain behaviour in rats. In this model, 100 µL of 1% carrageenan was subcutaneously injected into the plantar aspect of the right hind paw and exploratory behaviour in the novel testing chamber was recorded using an automated locomotor activity system.

RESULTS

Carrageenan-injected animals exhibited an exploratory behavioural deficit 2-7 h following injection compared to saline-injected animals. The severity of impairment was carrageenan dose related, and sensitive to the light intensity in the testing room. The effects of standard analgesics on CLAIM were examined 2 or 3 h following carrageenan injection. Diclofenac and ibuprofen, in a dose range exerting no effect on locomotor activity in naïve rats, exhibited dose-related reversal of CLAIM (ED(50) = 1.5 and 5.0 mg/kg, respectively), with comparable efficacy on carrageenan-induced thermal hyperalgesia (ED(50) = 2.0 and 6.0 mg/kg, respectively). Gabapentin and duloxetine produced no reversal of CLAIM, or attenuation of thermal hyperalgesia. Efficacy discrepancy was noted for morphine on thermal hyperalgesia and CLAIM. Additionally, amphetamine dose dependently reversed CLAIM, and similarly increased locomotor activity in normal animals.

DISCUSSION AND CONCLUSION

The results presented here demonstrate that CLAIM provides an objective assessment of non-evoked pain behaviours for acute inflammatory pain. The pharmacological profile of standard analgesics supports that CLAIM model can be used to identify agents to treat acute inflammatory pain in the clinic.

Peripheral and central sites of action for the non-selective cannabinoid agonist WIN 55,212-2 in a rat model of post-operative pain

BACKGROUND AND PURPOSE

Activation of cannabinoid (CB) receptors decreases nociceptive transmission in inflammatory or neuropathic pain states. However, the effects of CB receptor agonists in post-operative pain remain to be investigated. Here, we characterized the anti-allodynic effects of WIN 55,212-2 (WIN) in a rat model of post-operative pain.

EXPERIMENTAL APPROACH

WIN 55,212-2 was characterized in radioligand binding and in vitro functional assays at rat and human CB(1) and CB(2) receptors. Analgesic activity and site(s) of action of WIN were assessed in the skin incision-induced post-operative pain model in rats; receptor specificity was investigated using selective CB(1) and CB(2) receptor antagonists.

KEY RESULTS

WIN 55,212-2 exhibited non-selective affinity and agonist efficacy at human and rat CB(1) versus CB(2) receptors. Systemic administration of WIN decreased injury-induced mechanical allodynia and these effects were reversed by pretreatment with a CB(1) receptor antagonist, but not with a CB(2) receptor antagonist, given by systemic, intrathecal and supraspinal routes. In addition, peripheral administration of both CB(1) and CB(2) antagonists blocked systemic WIN-induced analgesic activity.

CONCLUSIONS AND IMPLICATIONS

Both CB(1) and CB(2) receptors were involved in the peripheral anti-allodynic effect of systemic WIN in a pre-clinical model of post-operative pain. In contrast, the centrally mediated anti-allodynic activity of systemic WIN is mostly due to the activation of CB(1) but not CB(2) receptors at both the spinal cord and brain levels. However, the increased potency of WIN following i.c.v. administration suggests that its main site of action is at CB(1) receptors in the brain.

In vitro and in vivo characterization of A-796260: a selective cannabinoid CB2 receptor agonist exhibiting analgesic activity in rodent pain models

BACKGROUND AND PURPOSE

Selective cannabinoid CB2 receptor agonists have demonstrated analgesic activity across multiple preclinical pain models. AM1241 is an indole derivative that exhibits high affinity and selectivity for the CB2 binding site and broad spectrum analgesic activity in rodent models, but is not an antagonist of CB2 in vitro functional assays. Additionally, its analgesic effects are mu-opioid receptor-dependent. Herein, we describe the in vitro and in vivo pharmacological properties of A-796260, a novel CB2 agonist.

EXPERIMENTAL APPROACH

A-796260 was characterized in radioligand binding and in vitro functional assays at rat and human CB1 and CB2 receptors. The behavioural profile of A-796260 was assessed in models of inflammatory, post-operative, neuropathic, and osteoarthritic (OA) pain, as well as its effects on motor activity. The receptor specificity was confirmed using selective CB1, CB2 and mu-opioid receptor antagonists.

KEY RESULTS

A-796260 exhibited high affinity and agonist efficacy at human and rat CB2 receptors, and was selective for the CB2 vs CB1 subtype. Efficacy in models of inflammatory, post-operative, neuropathic and OA pain was demonstrated, and these activities were selectively blocked by CB2, but not CB1 or mu-opioid receptor-selective antagonists. Efficacy was achieved at doses that had no significant effects on motor activity.

CONCLUSIONS AND IMPLICATIONS

These results further confirm the therapeutic potential of CB2 receptor-selective agonists for the treatment of pain. In addition, they demonstrate that A-796260 may be a useful new pharmacological compound for further studying CB2 receptor pharmacology and for evaluating its role in the modulation of pain.

Differential effects of cannabinoid receptor agonists on regional brain activity using pharmacological MRI

BACKGROUND AND PURPOSE

Activation of cannabinoid CB1 and/or CB2 receptors mediates analgesic effects across a broad spectrum of preclinical pain models. Selective activation of CB2 receptors may produce analgesia without the undesirable psychotropic side effects associated with modulation of CB1 receptors. To address selectivity in vivo, we describe non-invasive, non-ionizing, functional data that distinguish CB1 from CB2 receptor neural activity using pharmacological MRI (phMRI) in awake rats.

EXPERIMENTAL APPROACH

Using a high field (7 T) MRI scanner, we examined and quantified the effects of non-selective CB1/CB2 (A-834735) and selective CB2 (AM1241) agonists on neural activity in awake rats. Pharmacological specificity was determined using selective CB1 (rimonabant) or CB2 (AM630) antagonists. Behavioural studies, plasma and brain exposures were used as benchmarks for activity in vivo.

KEY RESULTS

The non-selective CB1/CB2 agonist produced a dose-related, region-specific activation of brain structures that agrees well with published autoradiographic CB1 receptor density binding maps. Pretreatment with a CB1 antagonist but not with a CB2 antagonist, abolished these activation patterns, suggesting an effect mediated by CB1 receptors alone. In contrast, no significant changes in brain activity were found with relevant doses of the CB2 selective agonist.

CONCLUSION AND IMPLICATIONS

These results provide the first clear evidence for quantifying in vivo functional selectivity between CB1 and CB2 receptors using phMRI. Further, as the presence of CB2 receptors in the brain remains controversial, our data suggest that if CB2 receptors are expressed, they are not functional under normal physiological conditions.

Activators of soluble guanylate cyclase for the treatment of male erectile dysfunction

Soluble guanylate cyclase (sGC) is an important enzyme in corpus cavernosum smooth muscle cells as it is one of the regulators of the synthesis of cGMP. The efficacy of sildenafil (Viagra) in the treatment of male erectile dysfunction indicates the importance of the cGMP system in the erectile response as the increased levels of cGMP induce relaxation of the corpus cavernosum. sGC is physiologically activated by nitric oxide (NO) during sexual stimulation, and its activity can be pharmacologically enhanced by several NO-donors. Agents like YC-1 can also activate sGC after binding to a novel allosteric site in the enzyme, a site different from the NO binding site. YC-1 can relax rabbit cavernosal tissue and it facilitates penile erection in vivo. This review summarizes the enzymology, biochemistry and pharmacology of this novel allosteric site and its relevance for the regulation of penile function. This type of sGC activators represent a new class of compounds with a different pharmacological profile in comparison to the classical NO-donors and they could be beneficial for the treatment of male erectile dysfunction.

Dual mechanism of action of nicorandil on rabbit corpus cavernosal smooth muscle tone

The potential of ATP-sensitive potassium channel openers (KCOs) for the treatment of male erectile dysfunction has recently been suggested based on positive clinical outcomes following intra-cavernosal administration of pinacidil. Agents that increase the levels of cGMP via elevation of nitric oxide (NO) nitroglycerin, for example, are also effective in improving erectile function preclinically and clinically. The aim of the present study was to determine the effects and mechanism of the action of nicorandil on rabbit corpus cavernosum. The in vitro regulation of smooth muscle tone was assessed in isolated cavernosal tissues pre-contracted with phenylephrine. Nicorandil, but not its major metabolite, relaxed phenylephrine-precontracted cavernosum smooth muscle with an EC(50) of 15 microM. The effects of nicorandil were only partially reversed by the K(ATP) channel blocker glyburide (10 microM) or by a soluble guanylate cyclase (sGC) inhibitor 1H-[1,2,4] oxadiazole [4,3-a] quinoxalin-1-one (ODQ, 3 microM). However, a combination of ODQ and glyburide completely blocked the relaxant effects of nicorandil. The results of the present study indicate that nicorandil can relax rabbit cavernosal tissue in vitro via a mechanism that involves activation of K(ATP) channels and stimulation of soluble guanylate cyclase.

Low valsalva leak-point pressure and success of retropubic urethropexy

The aim of this study was to determine whether an isolated low Valsalva leak-point pressure (VLPP) is predictive of intrinsic sphincter deficiency (ISD) and can be an independent risk factor for retropubic urethropexy failure in patients with a normal maximal urethral closure pressure (MUCP). Twenty-four women with urodynamically proven genuine stress incontinence with low VLPP (<60 cmH2O) and normal MUCP (>20 cmH2O) were evaluated subjectively and objectively by complex urodynamic testing before and after undergoing a modified Burch urethropexy. Success rates were then compared to historical success rates for subjects with ISD treated with retropubic urethropexy using an exact one-sample test for binomial proportions. Patients were followed postoperatively for a mean of 11.1 months, with a range of 5-16 months. Twenty-two of the 24 (91.7%) were continent on postoperative cystometry. This differs significantly from the published success rates of 50% (P < 0.001), if a low VLPP alone were predictive of ISD. Retropubic urethropexy was successful in the majority of our patients with genuine stress incontinence with a low VLPP and normal MUCP.

3,5-Bis(trifluoromethyl)pyrazoles: a novel class of NFAT transcription factor regulator

A series of bis(trifluoromethyl)pyrazoles (BTPs) has been found to be a novel inhibitor of cytokine production. Identified initially as inhibitors of IL-2 synthesis, the BTPs have been optimized in this regard and even inhibit IL-2 production with a 10-fold enhancement over cyclosporine in an ex vivo assay. Additionally, the BTPs show inhibition of IL-4, IL-5, IL-8, and eotaxin production. Unlike the IL-2 inhibitors, cyclosporine and FK506, the BTPs do not directly inhibit the dephosphorylation of NFAT by calcineurin.

Neointimal formation after balloon-induced vascular injury in Yucatan minipigs is reduced by oral rapamycin

Rapamycin, a macrolide antibiotic known to prevent allograft rejection, is a potent inhibitor of cell proliferation. Therefore we studied the effects of orally administered rapamycin in a pig model of balloon injury in an attempt to reduce the cellular proliferation and neointimal formation thought to play a role in restenosis. Twenty Yucatan minipigs, divided into groups of 10 animals each, were subjected to balloon inflation of the carotid arteries. One group received the methylcellulose vehicle for rapamycin, whereas the second group was treated for a total of 31 days with 2.0 mg/kg of rapamycin administered daily by oral gavage. This dose and treatment regimen produced significant (p < 0.05) reductions in neointimal area (59%) and in the maximal thickness of the neointima (59%) when comparisons were made with vehicle-treated animals. These effects were accompanied by a significant increase in the lumen area in animals that received rapamycin (33%). Medial area was decreased by 18% in these animals. Blood samples from rapamycin-treated pigs indicated peak concentrations of 1.87 +/- 0.45 and 1.70 +/- 0.24 ng/ml at 2 and 4 weeks after balloon angioplasty, respectively. Significant increases in blood pressure of 21 mm Hg and decreases in heart rate of 25 beats/min also were observed in rapamycin-treated animals relative to those that received vehicle. These results indicate that the antiproliferative effect of rapamycin can be demonstrated after oral dosing in a pig vascular injury model, suggesting a possible therapeutic utility for rapamycin or its analogs in patients undergoing balloon angioplasty.

A macrolactam inhibitor of T helper type 1 and T helper type 2 cytokine biosynthesis for topical treatment of inflammatory skin diseases

T lymphocytes play a critical part in inflammatory skin diseases but are targeted by available therapies that have only partial efficacy, significant side-effects, or both. Because psoriasis, atopic dermatitis, and allergic contact hypersensitivity are associated with T helper type 1 (Th1), T helper type 2 (Th2), or mixed Th1-Th2 cell subsets and cytokine types, respectively, there is a need for a better broad-based inhibitor. The macrolactam ascomycin analog, ABT-281, was found to inhibit potently T cell function across species and to inhibit expression of multiple cytokines in human peripheral blood leukocytes which have been found in human skin disease cells and tissues. These included immunoregulatory Th1 (interleukin-2 and interferon-gamma) and Th2 (interleukin-4 and interleukin-5) cytokines. ABT-281 was shown to have potent topical activity (ED50 = 0.6% in acetone/olive oil) in a stringent swine model of allergic contact hypersensitivity, but its potency was markedly reduced compared with ascomycin when administered systemically due to more rapid clearance. Topical application of 3% ABT-281 in acetone/olive oil over 25% of the body surface in swine resulted in undetectable blood levels. Compared with a wide potency range of topical corticosteroids in clinical formulations, 0.3% and 1% ABT-281 ointments profoundly inhibited dinitrochlorobenzene-induced contact hypersensitivity in the pig by 78% and 90%, respectively, whereas super-potent steroids such as clobetasol propionate only inhibited in the 50% range and mild to moderate potency steroids such as fluocinolone acetonide were inactive. The potent topical activity of ABT-281 in swine, its superior efficacy, its rapid systemic clearance following uptake into the bloodstream, and its ability to inhibit cytokine biosynthesis of both Th1 and Th2 cell subsets, suggests that it will have a broad therapeutic value in inflammatory skin diseases, including psoriasis, atopic dermatitis, and allergic contact dermatitis.

Ex vivo assessment of immunosuppression in undiluted whole blood from pigs dosed with tacrolimus (FK506)

To assess the duration of immunosuppression in FK506-dosed pigs, an undiluted whole blood assay was established to measure reactivities of T cells in their physiological milieu. PMA and ionomycin were shown to induce IL-2 production in swine blood. The IC50 of FK506 in inhibiting IL-2 production in whole blood and isolated PBMC stimulated with PMA and ionomycin measured 1.2 and 0.04 nM, respectively. These data underscore the influence of red blood cells and plasma proteins on drug potency. IL-2 levels were determined in blood drawn immediately before and 1, 24, 48, and 72 h after iv dosing. For pigs dosed with 0.05 mg/kg, 50% recovery of IL-2 production was observed at 16 h and 100% at 35 h after dosing. For pigs dosed with 0.15 mg/kg, 50% recovery was observed at 38 h and 100% at 72 h. Blood concentrations of FK506 at 50 and 100% recovery of IL-2 production measured 10.8 and 2.2 nM for pigs dosed with 0.05 mg/kg and 6.1 and 1.1 nM for pigs dosed with 0.15 mg/kg, respectively. These concentrations are severalfold higher than predicted from the IC50 of FK506 for inhibiting IL-2 production in the whole blood assay. These data suggest that the true potency of FK506 in blood after dosing is influenced by additional factors, which could include plasma protein binding, the presence of active or interfering metabolites, serum interfering factors, and sequestration of drug in blood cells. Our results demonstrate the utility of an undiluted whole blood assay for assessing the duration of immunosuppression in drug-dosed animals and emphasize the importance of assessing drug potency in the whole blood environment ex vivo.

Synthesis and immunosuppressant activity of pyrazole carboxamides

A series of novel pyrazole carboxamides is disclosed that demonstrate strong immunosuppressant activity in rodent and human mixed leukocyte response (MLR) assays (IC50 < 1 microM). The synthesis, biological activity, mode of action, and pharmacokinetic properties of this new lead series are discussed.

Studies on an immunosuppressive macrolactam, ascomycin: synthesis of a C-33 hydroxyl derivative

Ascomycin 2, a close analogue of the immunosuppressant FK506 1, was modified to incorporate a hydroxyl group at the C-33 position. This increased the aqueous solubility of ascomycin by a hundred-fold at pH 7.4 and by approximately 300-fold at pH 6.5. Ascomycin 3 also exhibited an excellent immunosuppressive activity in vitro, as tested in a human mixed lymphocyte proliferation (HuMLR) assay, and in vivo using a rat popliteal lymph node (rPLN) hyperplasia assay.

Nephrotoxicity studies of the immunosuppressants tacrolimus (FK506) and ascomycin in rat models

The nephrotoxic potential of ascomycin, the C21-ethyl analogue of FK506, was defined and ways explored to enhance its detection. After 14-day dosing in the Fischer-344 rat, FK506 and ascomycin reduced creatinine clearance by >50% at doses of 1 and 3 mg/kg, i.p., respectively. Ascomycin also had a 3-fold lower immunosuppressive potency in a popliteal lymph node hyperplasia assay, resulting in an equivalent therapeutic index consistent with a common mechanistic dependence on calcineurin inhibition. Renal impairment with different routes of administration was correlated with pharmacokinetics. Sensitivity of detection was not adequate with shorter dosing durations in rats with unilateral nephrectomy or in mice using a cytochrome P-450 inhibitor, SKF-525A. In 14-day studies, nephrotoxicity was not induced by continuous i.p. infusion of ascomycin at 10 mg/kg/day or daily oral administration (up to 50 mg/kg/day) in rats on a normal diet, nor by continuous i.v. infusion (up to 6 mg/kg/day) in rats on a low salt diet to enhance susceptibility. The lack of toxicity at high oral doses of FK506 or ascomycin, and the finding of non-linear oral pharmacokinetics of ascomycin show that this drug class has an oral absorption ceiling. The negative results with continuous infusion suggest that ascomycin nephrotoxicity is governed by peak drug levels. In addition to defining ways to meaningfully compare the nephrotoxic potential of FK506 derivatives, these results have implications for overall safety assessment and improved clinical use.

Improved methods for transplanting split-heart neonatal cardiac grafts into the ear pinna of mice and rats

The rodent heterotopic ear-heart transplant method is a useful alternative to the more technically demanding vascularized graft technique. We modified the procedure to improve efficiency and used it in mice and rats to determine the survival times of both isologous and allogeneic grafts and compare reference immunosuppressants. Bisected rat and mouse cardiac (split-heart) isografts were uniformly viable up to 4 weeks postimplant; however, by 24 weeks only 90% of Lewis rat or C3H mouse split-heart isografts retained electrocardiographic activity, regressing to 81% by 60 weeks for the Lewis rat and to less than 50% for the C3H mouse by 43 weeks post-implant. The potency of tacrolimus, sirolimus, and cyclosporine for prevention of allograft rejection was comparable whether using split-hearts or whole hearts in the Balb/C to C3H mouse model. The maximally effective doses at 2 weeks postimplant for intraperitoneally administered tacrolimus, sirolimus, cyclosporine, and oral leflunomide with Brown-Norway (BN) to Lewis rat ear-split-heart allografts (0.3, 0.1, 3.0, 10, mg/kg/day, respectively) agreed extremely well with published data for the rat primary vascularized heterotopic heart model. This reproducible and efficient transplantation model was improved by using split-hearts to double available donor tissue, a gonadotropin-enhanced breeding strategy that enables routine use of low-fecundity inbred rats as donors, implantation devices that speed and simplify the procedure, and defined electrocardiographic evaluation criteria to maximize sensitivity and provide an objective endpoint for defining rejection.

Discovery of less nephrotoxic FK506 analogs and determining immunophilin dependence of immunosuppressant nephrotoxicity with a novel single-dose rat cisplatin potentiation assay

Comparing nephrotoxicity of numerous drug analogs is impractical with chronic in vivo models. We devised a new cisplatin potentiation assay (CISPA) that sensitively detects renal injury as a serum creatinine increase when only one dose of test compound is followed by cisplatin. Reference nephrotoxins known to act on various sites in kidney tubules, glomeruli or renal papilla were all detected by the CISPA at single doses that without cisplatin gave little change, which showed that this simple, sensitive assay has broad potential utility for mechanistic studies of nephrotoxicity. We used the CISPA both to probe the nephrotoxic mode of action of immunosuppressants and to search for safer compounds. Although several non-nephrotoxic immunosuppressants were inactive, cyclosporine, FK506, ascomycin (C21-ethyl-FK506) and rapamycin were nephrotoxic in the CISPA at single doses equal to the daily amounts required to reduce creatinine clearance with 14 days of treatment. Similar therapeutic indices were derived comparing toxicity by either method to prevention of rat ear-heart allograft rejection. C18-OH-ascomycin, an FK506-binding protein (FKBP) antagonist, reversed in vivo immunosuppression by FK506 and ascomycin in the rat, and pretreatment in the CISPA blocked FK506 and ascomycin nephrotoxicity, which showed a common immunophilin dependence. Rapamycin nephrotoxicity was unaffected (as with cyclosporine), which indicated that binding to FKBP was not required. Rapamycin nephrotoxicity thus appears mechanistically unrelated to its immunosuppressive mode of action. Screening with the CISPA enabled discovery of A-119435, a less nephrotoxic ascomycin analog having a 10-fold higher therapeutic index.

Transcription function of each base pair in the control region of the adenovirus VARNA1 gene

Eighty-seven mutants with single-base substitution in the control region (from -44 to +70) of the adenovirus VARNA1 gene were generated, including nearly every base pair, to examine the role of DNA sequences within this control region for regulating transcription. The effect of these mutations on transcription of the gene was determined in vitro using cytoplasmic S100 extracts from human KB cells. Mutations at -37T, -35A, -29T, -28A, -25C, -18A, -17A, -16A, -13A, -9C, -8C, and -1C in the 5'-flanking region reduced transcription of the gene. Thus two positive regulatory elements, from -44 to -25 and from -18 to +2, interspersed with a putative negative regulatory element were defined. Furthermore, a distinct A-rich purine stretch in the -18 to +2 element was identified. Point mutations in the pyrimidine-rich sequence immediately upstream of the A block promoter element reduced transcription of the gene. Mutations in the GTGG direct repeats of the A block promoter element drastically decreased transcription. Furthermore, mutations that altered the AT-rich sequence immediately downstream of the A block element to become less AT-rich decreased transcription. Mutations of the base pairs at +43C, +45T, and +51A in the inter-block element moderately reduced transcription efficiency of the gene. Mutations at the central four base pairs, GTTC, of the B block palindrome severely affected transcription. These unique sequence motifs and their exact base pairs were proven to be important for regulating transcription of the VARNA1 gene.

Structure-activity profiles of macrolactam immunosuppressant FK-506 analogues

The immunosuppressive agent FK-506 has received much attention due to its efficacy and potency in the areas of transplant rejection and autoimmune disease. Calcineurin, a Ca(2+)-calmodulin activated phosphatase, was recently implicated in the immunosuppressive mechanism of FK-506. In our ongoing search for superior immunosuppressive agents, we have synthesized several analogues of FK-506 and tested their mechanistic and immunosuppressive actions. It was found that C-18 hydroxyl analogues of ascomycin, an analogue of FK-506 also called FR900520, bound tightly to immunophilin FKBP-12, but do not show any immunosuppressive activity in vitro or in vivo despite good bioavailability. Further, they reverse the inhibition of calcineurin caused by FK-506/FKBP-12 complex.

Immunological and neurobiochemical alterations induced by repeated oral exposure of phenol in mice

Phenol, a major metabolite of benzene, is a potentially immunotoxic and neurotoxic substance of environmental significance. Male CD-1 mice were continuously exposed to 0, 4.7, 19.5, and 95.2 mg phenol/l in drinking water for 4 weeks. Various immune functions were evaluated and levels of selected neurotransmitters and metabolites measured in discrete brain regions. The doses of phenol did not produce any overt clinical signs of toxicity; peripheral red blood cell counts and hematocrits decreased. A dose of 95.2 mg/l suppressed the stimulation of cultured splenic lymphocytes by lipopolysaccharide, pokeweed mitogen, and phytohemagglutinin and the response in mixed lymphocyte cultures. The two high doses suppressed antibody production response to the T cell-dependent antigen (sheep erythrocytes), as determined by plaque-forming cells, and serum antibody levels. Mice treated with phenol had lower levels of neurotransmitters in several brain regions. In the hypothalamus, a major norepinephrine-containing compartment, the concentrations of norepinephrine significantly decreased by 29 and 40% in groups dosed with 19.5 and 95.2 mg/l, while dopamine concentrations decreased in the corpus striatum by 21, 26, and 35% at 4.7, 19.5 and 95.2 mg/l, respectively. Phenol also decreased 5-hydroxytryptamine in the hypothalamus, medulla oblongata, midbrain and corpus striatum. Levels of monoamine metabolites decreased in the hypothalamus (5-hydroxyindoleacetic acid), midbrain (vanillylmandelic acid), corpus striatum (vanillylmandelic acid and dihydroxyphenylacetic acid), cortex (vanillylmandelic acid), and cerebellum (dihydroxyphenylacetic acid).

Toxicity assessment of toxins T-514 and T-544 of buckthorn (Karwinskia humboldtiana) in primary skin and liver cell cultures

The present study was undertaken to assess and compare the in vitro cytotoxicity of toxins T-514 and T-544 of Buckthorn (Karvinskia humboldtiana) using primary cultures of rat hepatocytes and keratinocytes. Cell cultures were exposed to 6, 12, 25 and 50 microM concentrations of the toxins for 2, 4, 6 and 24-h periods. Cytotoxicity was determined by release of the cytoplasmic enzyme, lactate dehydrogenase (LDH), in culture media, methylthiazoltetrazolium (MTT) reduction and neutral red (NR) uptake. An increase in LDH leakage was observed in liver cell cultures as early as 2 h with 50 microM T-544 and with 6 microM T-514 and T-544 at 6 h and 24 h, respectively. In the NR assay the toxicity was evident at 2 h with 12 microM T-514 and T-544 and with 6 microM concentrations of both toxins at 6 h. On the other hand, a decrease in MTT reduction was detected at 4 h with 50 microM concentrations of both toxins and with 25 microM T-544 and 12 microM T-514 at 6 h and 6 microM T-514 and T-544 at 24 h. Both toxins were shown to be highly hepatotoxic; T-514 was more toxic than T-544. In the skin cell cultures, the toxicity of the toxins was not as severe and was not expressed until 12 h of exposure.

Toxicity assessment of toxins T-514 and T-544 of buckthorn (Karwinskia humboldtiana) in primary skin and liver cell cultures

The present study was undertaken to assess and compare the in vitro cytotoxicity of toxins T-514 and T-544 of buckthorn (Karwinskia humboldtiana) using primary cultures of rat hepatocytes and keratinocytes. Cell cultures were exposed to 6, 12, 25 and 50 microM toxins for 2-, 4-, 6- and 24-h periods. Cytotoxicity was determined by release of the cytoplasmic enzyme, lactate dehydrogenase (LDH), in culture media, methylthiazoltetrazolium (MTT) reduction and neutral red (NR) uptake. An increase in LDH leakage was observed in liver cell cultures as early as 2 h with 50 microM T-544 and with 6 microM T-514 and T-544 at 6 h and 24 h, respectively. In the NR assay the toxicity was evident at 2 h with 12 microM T-514 and T-544 and with 6 microM concentrations of both toxins at 6 h. On the other hand, a decrease in MTT reduction was detected at 4 h with 50 microM concentrations of both toxins and with 25 microM T-544 and 12 microM T-514 at 6 h and 6 microM T-514 and T-544 at 24 h. Both toxins were shown to be highly hepatotoxic; T-514 was more toxic than T-544. In the skin cell cultures, the toxicity of the toxins was not as severe and was not expressed until 12 h of exposure.

Dithranol-induced cytotoxicity in primary cultures of rat epidermal keratinocytes. I. The role of reactive oxygen species

Primary cultured rat epidermal keratinocytes were used as an experimental model to detect oxidant-mediated adverse effects of dithranol (anthralin), a widely used antipsoriasis drug with tumor-promoting and skin-irritating properties. Keratinocytes were isolated and prepared from the skin of neonatal rats by a trypsin flotation method. Highly proliferative monolayer cells cultured in a serum-free medium were exposed to the test compound at concentrations (5-100 microM) used therapeutically for the treatment of skin disorders. Cytotoxicity was evaluated by changes in plasma membrane integrity (lactate dehydrogenase leakage), lysosomal function (neutral red uptake), and mitochondrial metabolic activity (reduction of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide, MTT). Exposure of keratinocytes to dithranol produced time- and concentration-related toxic responses. MTT reduction was found to be a more sensitive endpoint of cytotoxicity, showing significant toxic effects at 2 hr, while significant leakage of lactate dehydrogenase did not result until 6 hr. Oxygen consumption in keratinocytes and isolated mitochondria showed a similar pattern after exposure to dithranol. Increased cyanide-insensitive respiration was also noted. Oxidative stress, measured by superoxide anion-dependent reduction of nitroblue tetrazolium, occurred before dithranol produced cytotoxicity in the keratinocyte cultures. Superoxide formation, which increased with time after dithranol exposure, was detected both extracellularly and intracellularly and was inhibited by the addition of superoxide dismutase. Dithranol-induced cell injury was partially prevented by treatment with superoxide dismutase, and greater protection was shown by concurrent treatment with superoxide dismutase plus catalase. These findings suggest that the superoxide anion and hydrogen peroxide may be involved in the cytotoxicity of dithranol and that a culture system of rat keratinocytes may be useful in evaluating the mechanism of toxicity of dermatotoxicants.

Hypothalamic-pituitary-adrenocortical axis activity and immune function after oral exposure to benzene and toluene

Benzene and toluene, commonly used solvents, possess neurotoxic and immunotoxic effects. Male CD-1 mice were continuously fed drinking water containing 0, 31, 166 and 790 mg/l benzene and 0, 17, 80 and 405 mg/l toluene, respectively. The concentrations of hypothalamic norepinephrine (NE) and its metabolite vanillylmandelic acid (VMA), circulating corticosterone and adrenocorticotropic hormone (ACTH), and lymphocyte-derived interleukin-2 (IL-2) activity were evaluated after 28 days of exposure to each solvent. Serum corticosterone was also measured at pretreatment, 2, 7, and 14 days of exposure. The concentrations of NE, VMA, ACTH and corticosterone were increased following exposure to these solvents. Benzene increased corticosterone levels in mice after 7 days (166 and 790 mg/l) and at 28 days (790 mg/l). Toluene elevated corticosterone levels at 14 and 28 days at the 405 mg/l exposure. IL-2 production by mouse T-lymphocytes was suppressed in the two higher benzene-treated groups, while toluene decreased IL-2 synthesis at the highest level only. Both benzene and toluene exposures stimulated hypothalamic-pituitary-adrenocortical (HPA) activity. Elevated corticosterone has been reported to inhibit IL-2 production and impair immunocompetence. Organic solvents may have, at least partially, an additive adverse effect on immune function via activated HPA status.

Effects of Cordyceps sinensis on murine T lymphocyte subsets

It was shown by flow cytometry analysis that crystalized preparation of Cordyceps sinensis (Cs-Cr) caused significant elevation of the number of T helper cells and Lyt-1/Lyt-2 (T helper to T suppressor cell) ratio both in peripheral blood and the treated mice spleen. The spleen weight, phagocyte counts and phagocytic activity were also elevated in the treated group. In addition, Cs-Cr could protect T helper cells from the immunosuppressive effects of prednisolone acetate and cyclophosphamide. These results further substantiate the fact that Cs-Cr is an immunoregulator/biological response modifier of cellular immunity and may be potentially useful in handling immunodeficient or immunosuppressed patients.

Subclinical effects of groundwater contaminants. IV. Effects of repeated oral exposure to combinations of benzene and toluene on regional brain monoamine metabolism in mice

Benzene and toluene are known neurotoxicants that may interact in vivo. The effect of combined treatment with benzene and toluene on the endogenous concentrations of the catecholamines norepinephrine (NE) and dopamine (DA), the catecholamine metabolites vanillylmandelic acid (VMA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the indoleamine serotonin (5-HT) and its metabolite 5-hydroxy-indoleacetic acid (5-HIAA), were investigated in six discrete brain regions of CD-1 mice. Groups of male, adult mice were continuously exposed to benzene (166 mg/l), toluene (80 and 325 mg/l), and combinations of benzene + toluene (80 or 325 mg/l) in drinking water for 4 weeks. Benzene produced increases of NE in the hypothalamus, cortex, midbrain and medulla oblongata, DA in the hypothalamus and corpus striatum, and 5-HT in all dissected brain regions except cerebellum. Elevated levels of various monoamine metabolites were also observed in these brain areas. Toluene ingestion alone also significantly increased the concentrations of NE, DA, 5-HT, and their metabolites in several brain regions. Mice given the combined treatments exhibited raised regional neurochemical levels when compared to the untreated controls. Increased concentrations of biogenic amine metabolites in several brain regions were greater in the combined exposures of benzene and toluene than when either chemical was used alone. The findings were different from those observed on immune parameters using similar treatment protocols, where simultaneous exposure to toluene prevented the immunotoxic effects of benzene.

Cytotoxicity induced by papaverine hydrochloride in fungal cell systems

Cunninghamella echinulata was used to assess the cytotoxicity of papaverine (papaver), at concentrations ranging from 1 x 10(-5) to 1 x 10(-3) M for 1-6 days. Leakage of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT), and changes in alkaline phosphatase (AP) activity and lactate/pyruvate (L/P) ratios were used as indices of cytotoxicity. Leakage of LDH occurred at the 6th day with 1 x 10(-3) M; AP activity and L/P ratios decreased after 6 days treatment with 1 x 10(-4) M, after 1 day with 1 x 10(-3) M, and after 3 days with 1 x 10(-4) M, respectively. This study provides support for the use of fungal cell systems to evaluate the toxicity of drugs and chemicals.

Subclinical effects of groundwater contaminants. III. Effects of repeated oral exposure to combinations of benzene and toluene on immunologic responses in mice

Toxicity of environmental pollutants may be expressed as combined effects of a chemicals. Benzene, a proven hematotoxic agent, frequently occurs with toluene in cocontaminated groundwater. Groups of CD-1 male mice were exposed continuously for 4 weeks to benzene (166 mg/l), toluene (80 and 325 mg/l), and combinations of benzene (166 mg/l) + toluene (80 mg/l or 325 mg/l) in drinking water. Benzene-induced anemia was alleviated by simultaneous toluene treatment. Leukopenia and lymphopenia were observed in the case of benzene only and benzene + toluene (80 mg/l)-treated mice. The cytopenia, however, was less severe in the benzene + toluene (325 mg/l)-treated group. Immunotoxicity induced by benzene treatment alone was characterized by involution of thymic mass and suppressions of both B- and T-cell mitogeneses, mixed lymphocyte culture response to alloantigens, the tumor lytic ability of cytotoxic T-lymphocytes as determined by 51Cr-release assay, and antibody production response to T-dependent antigen (sheep red blood cells). IL-2 secretion by Con A-stimulated mouse T-cells was decreased in the benzene-treated group. Toluene (325 mg/l) completely inhibited these adverse effects when it was coadministered with benzene, while the low dose of toluene (80 mg/l) did not protect against benzene-induced depressions of immune functions. Toluene administered alone at levels up to 325 mg/l showed no obvious immunotoxic effects. Results of this study demonstrated that toluene, in sufficient amounts, has an antagonistic effect on benzene immunotoxicity.