Serotonergic modulation of pain and analgesic responses: a study in rats with constitutionally altered serotonin transporters

BACKGROUND

A role of the serotonin (5HT) transporter, a key regulator of serotonergic transmission, in the physiology, pharmacology and genetics of pain responses has been proposed recently. The present study aimed to explore the impact of constitutive differences in the activity of the serotonin transporter, and 5HT homeostasis in general, on the modulation on pain sensitivity and analgesic responses to drugs that utilize 5HT mechanisms.

METHODS

A novel genetic animal model, Wistar-Zagreb 5HT rats, obtained by selective breeding of animals for extreme activity of the platelet serotonin transporter was used. As a consequence of breeding, two sublines of this model, termed high-5HT and low-5HT, differ in both central and peripheral serotonin homeostasis. Thermal pain sensitivity of 5HT sublines was assessed at baseline and following administration of analgesic drugs, as determined by paw withdrawal latency to radiant heat stimulation.

RESULTS

Animals from 5HT sublines show differences in both basal pain sensitivity and analgesic responses. Rats with the low-5HT phenotype displayed decreased baseline paw withdrawal latencies (hyperalgesia) in comparison to their high-5HT counterpart (25%; p < 0.001). They also showed better analgesic response to acute and prolonged treatment with tramadol (p = 0.027) and clomipramine (p = 0.019), respectively, whereas administration of fluvoxamine did not produce an analgesic effect in either 5HT subline.

CONCLUSIONS

These findings support the idea that functionality of the serotonin transporter is one of the physiological/genetic determinants of individual differences in pain responses and modulation. They also validate Wistar-Zagreb 5HT rats, with constitutionally up-regulated/down-regulated serotonin transporter, as a potential new genetic model for studying serotonergic modulation of pain responses.

Lipid peroxidation, detoxification capacity, and genome damage in mice after transplacental exposure to pharmaceutical drugs

Data on genome damage, lipid peroxidation, and levels of glutathione peroxidase (GPX) in newborns after transplacental exposure to xenobiotics are rare and insufficient for risk assessment. The aim of the current study was to analyze, in an animal model, transplacental genotoxicity, lipid peroxidation, and detoxification disturbances caused by the following drugs commonly prescribed to pregnant women: paracetamol, fluconazole, 5-nitrofurantoin, and sodium valproate. Genome damage in dams and their newborn pups transplacentally exposed to these drugs was investigated using the in vivo micronucleus (MN) assay. The drugs were administered to dams intraperitoneally in three consecutive daily doses between days 12 and 14 of pregnancy. The results were correlated, with detoxification capacity of the newborn pups measured by the levels of GPX in blood and lipid peroxidation in liver measured by malondialdehyde (HPLC-MDA) levels. Sodium valproate and 5-nitrofurantoin significantly increased MN frequency in pregnant dams. A significant increase in the MN frequency of newborn pups was detected for all drugs tested. This paper also provides reference levels of MDA in newborn pups, according to which all drugs tested significantly lowered MDA levels of newborn pups, while blood GPX activity dropped significantly only after exposure to paracetamol. The GPX reduction reflected systemic oxidative stress, which is known to occur with paracetamol treatment. The reduction of MDA in the liver is suggested to be an unspecific metabolic reaction to the drugs that express cytotoxic, in particular hepatotoxic, effects associated with oxidative stress and lipid peroxidation.

The antitumor activity of thymoquinone and thymohydroquinone in vitro and in vivo

AIM

The aim of the study was to investigate antitumor activity of thymoquinone (TQ) and thymohydroquinone (THQ) in vitro and in vivo.

MATERIALS AND METHODS

In the in vitro experiments, L929 mouse broblasts and two tumor cell lines (squamous cell carcinoma (SCC VII) and fibrosarcoma (FsaR)) were used. The cells were cultured with 0.1 or 0.01 mg/ml TQ or THQ for 24 h, and cytotoxicity assay was performed with the use of crystal violet staining technique. For in vivo antitumor efficiency evaluation of new compounds two murine tumor models (fibrosarcoma (FsaR) and squamous cell carcinoma (SCC VII)) were used. The used dose was equal for both substances. Antitumor effect of 4 intratumoral injections of TQ and THQ at the dose of 5 mg/kg was evaluated by comparison of tumor growth kinetics between treated and control animals.

RESULTS

In vitro study showed that TQ and THQ exhibit statistically significant cytotoxic activity (p less, similar 0.01). The cytotoxic activity was dose dependent and more expressed against tumor cells than against L929 fibroblasts. The result of antitumor activities of TQ and THQ in vivo reached TGI = 52% and it was statistically significant (p less, similar 0.05).

CONCLUSION

The results indicate that THQ antitumor activity may be improved with further dose increase of the investigated substance.

Antitumor efficiency of novel fluoro-substituted 6-amino-2-phenylbenzothiazole hydrochloride salts in vitro and in vivo

The purpose of this study was to investigate antitumor activity of novel fluoro-substituted 6-amino-2-phenylbenzothiazole hydrochloride salts in vitro and in vivo. A novel series of hydrochloride or dihydrochloride salts of the novel 2-(fluoro-substituted phenyl)-6-aminobenzothiazoles (5-7) have been prepared in multistep synthesis starting from 3- or 4-fluorobenzaldehydes and 2-amino-5-nitrothiophenol and evaluated for their antiproliferative activity against human cervical (HeLa), breast (MCF-7), colon (CaCO-2), and laryngeal (Hep-2) carcinomas and against fibroblast cell lines (WI-38). Also, antitumor activity of these compounds was evaluated in vitro and in vivo against murine melanoma (B16-F10), fibrosarcoma (FsaR), and squamous cell carcinoma (SCCVII). The tested compounds were found to exert good cytotoxic activity in vitro. The cytotoxic effect was selective, cell specific, and dose dependent, between 33 microM for MCF-7 and 110 microM for WI-38. Benzothiazoles reduced de novo protein and DNA synthesis up to 75%. All examined benzothiazoles had significant antitumor activity in vivo against melanoma B16-F10, fibrosarcoma, and squamous cell carcinoma. The best therapeutic results were achieved when therapy started 7 days after tumor cell implantation and when benzothiazoles were given repeatedly five times every 2 days, i.e., on day 7, 9, 11, 13, and 15 after transplantation of tumor cells.

Immunostimulatory effect of natural clinoptilolite as a possible mechanism of its antimetastatic ability

PURPOSE

Many biochemical processes are closely related to ion exchange, adsorption, and catalysis. Zeolites reversibly bind small molecules such as oxygen or nitric oxide; they possess size and shape selectivity, the possibility of metalloenzyme mimicry, and immunomodulatory activity. These properties make them interesting for pharmaceutical industry and medicine.

METHODS

The experiments were performed on mice. Different biochemical and molecular methods were used.

RESULTS

Micronized zeolite (MZ) administered by gastric intubation to mice injected with melanoma cells significantly reduced the number of melanoma metastases. In mice fed MZ for 28 days, concentration of lipid-bound sialic acid (LSA) in serum increased, but lipid peroxidation in liver decreased. The lymphocytes from lymph nodes of these mice provoked a significantly higher alogeneic graft-versus-host (GVH) reaction than cells of control mice. After i.p. application of MZ, the number of peritoneal macrophages, as well as their production of superoxide anion, increased. However, NO generation was totally abolished. At the same time, translocation of p65 (NFkappaB subunit) to the nucleus of splenic cells was observed.

CONCLUSION

Here we report antimetastatic and immunostimulatory effect of MZ and we propose a possible mechanism of its action.

Cell killing of melanoma B16 in vivo by hyperthermia and cytotoxins

The aim of this study was to investigate antitumour activity of cisplatin, dacarbasine, cyclophosphamide and a new compound from the nitrosourea group--acetamido-CNU ((2-chloroethyl)-1-nitroso-3-(methylenecarboxamido)-urea)--applied with or without local hyperthermia (43.5 degrees C/60 min). The tumour model for the investigation of antitumour activity was a mouse melanoma B16 transplanted into the footpad. Dacarbasine, cyclophosphamide and acetamido-CNU applied as a single treatment had statistically significant antitumour activity, while cisplatin applied as a single agent had no effect. Local hyperthermia alone had statistically significant antitumour activity. The best therapeutic effect (synergistic) was obtained when combined treatment (cytotoxins plus local hyperthermia) was used. Synergistic therapeutic results were achieved even when cisplatin and hyperthermia were combined, although cisplatin was ineffective when given as a single agent. Therapeutic results achieved with acetamido-CNU (newly synthesized compound) applied alone were similar to the therapeutic results achieved with dacarbasine or cyclophosphamide. In combined therapy (acetamido-CNU + HT), achieved therapeutic results were significantly better (p < 0.05) than results achieved by combining cisplatin and hyperthermia or dacarbasine and hyperthermia.

The effect of the zeolite clinoptilolite on serum chemistry and hematopoiesis in mice

Zeolites are natural or synthetic crystalline alumosilicates with ion exchanging properties. Supplied in fodder, they promote biomass production and animal health. Our aim was to assess the effects of the natural zeolite, clinoptilolite, on hematopoiesis, serum electrolytes and essential biochemical indicators of kidney and liver function in mice. Two preparations differing in particle size were tested: a powderized form obtained by countercurrent mechanical treatment of the clinoptilolite (MTCp) and normally ground clinoptilolite (NGCp). Young adult mice were supplied with food containing 12.5, 25 or 50% clinoptilolite powder. Control animals received the same food ration without the clinoptilolite. After 10, 20, 30 and 40 days, six animals from each group were exsanguinated to obtain blood for hematological and serum for biochemical measurements as well as to collect femoral bone marrow for determination of hematopoietic activity. Clinoptilolite ingestion was well tolerated, as judged by comparable body masses of treated and control animals. A 20% increase of the potassium level was detected in mice receiving the zeolite-rich diet, without other changes in serum chemistry. Erythrocyte, hemoglobin and platelet levels in peripheral blood were not materially affected. NGCp caused leukocytosis, with concomitant decline of the GM-CFU content in the bone marrow, which was attributed to intestinal irritation by rough zeolite particles. The mechanically treated clinoptilolite preparation caused similar, albeit less pronounced, changes. In a limited experiment, mice having transplanted mammary carcinoma in the terminal stage showed increased potassium and decreased sodium and chloride levels, severe anemia and leukocytosis, decreased bone marrow cellularity and diminished content of hematopoietic progenitor cells in the marrow. The clinoptilolite preparations ameliorated the sodium and chloride decline, whereas the effects on hematopoiesis were erratic.