Preclinical toxicity of innovative molecules: In vitro, in vivo and metabolism prediction.

The lack of predictivity of animal's models has increased the failure rate of drug candidates. Thus, the reversion of this scenario using preliminary in vitro assays and metabolism prediction can reduce the unnecessary use of animals, as well as predict toxic effects at preclinical and clinical stages. The present study aimed to evaluate safety of four biologically active molecules (RN104, RI78, ICH, PCH) with potential therapeutic applications synthesized in our laboratory. Initially, we used MTT cytotoxicity against A549, H9C2, HepG2, LLC-PK1 and NEURO-2 cell lines. RN104 showed the lowest cytotoxicity and further studies were conducted with it. The neutral red (NR) test was performed according to OECD-129 and then acute toxicity test (OECD-423). According to NR results we administered at 300 mg/kg on animals; however, no toxic effect was observed, while 2,000 mg/kg resulted in the death of one animal per group. After, metabolism prediction studies, performed using both ligand-based and structure-based, suggests three potential metabolites. In silico results suggested that potential metabolites could be fast eliminated and, then, this could be an explanation for lower observed toxicity in in vivo experiments. The results showed limitations of the NR as a predictor of the initial dose for the acute toxicity study, which may be related to metabolism. Therefore, the combination of theoretical and experimental studies is relevant to a general understanding of new molecule's toxicity.

Chlorinated metronidazole as a promising alternative for treating trichomoniasis.

Trichomoniasis is the most common non-viral, sexually transmitted infection affecting humans worldwide. The main treatment for trichomoniasis is metronidazole (MTZ). However, adverse effects and reports of resistance have stimulated the development of therapeutic alternatives. The ease of manipulation of the side chains of MTZ coupled with its safety makes this molecule attractive for the development of new drugs. In this context, we evaluated the activity of the chlorinated MTZ derivative, MTZ-Cl, on sensitive and resistant strains of Trichomonas vaginalis. MTZ-Cl presented a remarkable activity against both sensitive and resistant strains. In vitro and in vivo toxicity assays indicated that the new molecule is safe for future clinical trials. Furthermore, we noticed different rates of free radical production between the sensitive and resistant strains. MTZ-Cl induced a higher release of nitric oxide (NO, ~ 9000 a.u.) by both sensitive and resistant strains. However, the sensitive strain produced a greater amount of H2O2 (~ 1,800,000 a.u.) and superoxide radicals (~ 350,000 a.u.) in the presence of MTZ. In the resistant strain, production of these radicals was more prominent when MTZ-Cl was used. Collectively, these results suggest that NO is an important molecule in the trichomonacidal activity against resistant and sensitive strains, suggesting an alternative pathway for MTZ-Cl activation. We highlight the high trichomonacidal potential of MTZ-Cl, improving the effectiveness of treatment and reducing side effects. In addition, MTZ-Cl is derived from a well-established drug on the world market that presents low toxicity to human cells, suggesting its safety to proceed with future clinical trials.

Cyclic adenosine monophosphate protects renal cell lines against amphotericin B toxicity in a PKA-independent manner.

Amphotericin B is the "gold standard" agent in the management of serious systemic fungal infections. However, this drug can cause nephrotoxicity, which contributes up to 25% of all acute kidney injuries in critically ill patients. Cyclic adenosine monophosphate can protect kidney cells from death due to injury or drug exposure in some cases. Hence, the objective of this work was to evaluate if cAMP could prevent cell death that occurs in renal cell lines subjected to AmB treatment and, if so, to assess the involvement of PKA in the transduction of this signal. Two different renal cell lines (LLC-PK1 and MDCK) were used in this study. MTT and flow cytometry assays showed increased cell survival when cells were exposed to cAMP in a PKA-independent manner, which was confirmed by western blot. This finding suggests that cAMP (db-cAMP) may prevent cell death caused by exposure to AmB. This is the first time this effect has been identified when renal cells are exposed to AmB's nephrotoxic potential.

Toxicological in vitro and subchronic evaluation of LASSBio-596.

LASSBio-596, 2-[4-(1,4-tiazinan-4-ylsulfonyl) phenylcarbamoyl] benzoic acid, is an achiral compound containing a subunit carboxylic amide, was capable of preventing induced mechanical and morphological changes in the lungs that commonly caused the onset of asthma. Previous studies to determine the acute toxicity of oral LASSBio-596 at dose of 2000mg/kg caused no deaths in any of the tested animals. To further evaluate the safety of LASSBio-596, in vitro and in vivo tests were carried out. Regarding to in vitro test were used renal, hepatic, pulmonary, cardiac, neurologic and intestinal cell lines. They were evaluated using neutral red (NR) and [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assays. Micronuclei also was performed. Concerning to in vivo was performed subchronic on Wistar rats at doses of 10, 50, and 250mg/kg and zebrafish test. The in vitro tests results showed the safety of LASSBio-596. However, subchronic toxicity study results revealed changes in the blood parameters of amylase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), glucose and creatine kinase (CK) which is used for cardiotoxicity evaluation, although, did not identify any histopathological alterations. However, zebrafish test demonstrated cardiac damage. It was impossible to estimate the no-observed-adverse-effect-levels and lowest observed-adverse-effect level due to the presence of cardiotoxicity in all tested doses.

Role of protein kinase A signaling pathway in cyclosporine nephrotoxicity.

Cyclosporine is an important immunosuppressive agent; however, nephrotoxicity is one of the main adverse effects. The purpose of this study was to evaluate the effect of inhibiting the protein kinase A (PKA) signaling pathway in nephrotoxicity caused by cyclosporine from the assessment of cell viability, pro-inflammatory cytokines, and nitric oxide (NO) production in LLC-PK1 and MDCK cell lines. Cyclosporine proved to be cytotoxic for both cell lines, as assessed by the mitochondrial enzyme activity assay (MTT), caused DNA fragmentation, determined by flow cytometry using the propidium iodide dye, and activated the PKA pathway (western blot assay). In MDCK cells, the inhibition of the PKA signaling pathway (H89 inhibitor) caused a significant reduction in DNA fragmentation. In both cell lines, the production of IL-6 proved to be a dependent PKA pathway, while TNF-α was not influenced by the inhibition of the PKA pathway. The NO production was increased when cells were pre-incubated with H89 followed by cyclosporine, and this production was dependent on the PKA pathway in LLC-PK1 and MDCK cells lines. Therefore, considering the present study's results, it can be concluded that the inhibition of PKA signaling pathway can aid in reducing the degree of nephrotoxicity caused by cyclosporine.

Alteration in cellular viability, pro-inflammatory cytokines and nitric oxide production in nephrotoxicity generation by Amphotericin B: involvement of PKA pathway signaling.

Amphotericin B is one of the most effective antifungal agents; however, its use is often limited owing to adverse effects, especially nephrotoxicity. The purpose of this study was to evaluate the effect of inhibiting the PKA signaling pathway in nephrotoxicity using Amphotericin B from the assessment of cell viability, pro-inflammatory cytokines and nitric oxide (NO) production in LLC-PK1 and MDCK cell lines. Amphotericin B proved to be cytotoxic for both cell lines, as assessed by the mitochondrial enzyme activity (MTT) assay; caused DNA fragmentation, determined by flow cytometry using the propidium iodide (PI) dye; and activated the PKA pathway (western blot assay). In MDCK cells, the inhibition of the PKA signaling pathway (using the H89 inhibitor) caused a significant reduction in DNA fragmentation. In both cells lines the production of interleukin-6 (IL)-6 proved to be a dependent PKA pathway, whereas tumor necrosis factor-alpha (TNF-α) was not influenced by the inhibition of the PKA pathway. The NO production was increased when cells were pre-incubated with H89 followed by Amphotericin B, and this production produced a dependent PKA pathway in LLC-PK1 and MDCK cells lines. Therefore, considering the present study's results as a whole, it can be concluded that the inhibition of the PKA signaling pathway can aid in reducing the degree of nephrotoxicity caused by Amphotericin B.

Toxicological, toxicokinetic and gastroprotective evaluation of the benzaldehyde semicarbazone.

Benzaldehyde semicarbazone (BS) has presented positive results in several pharmacological models, including anticonvulsivant and anti-inflammatory models. The present study evaluated the preclinical toxicity (acute and subchronic), as well as the toxicokinetic and gastroprotective effects of BS against ethanol lesions. Oral doses of 300 and 2000mg/kg were used in the preclinical acute toxicity study; 100, 200, and 300mg/kg were used in both the subchronic toxicity evaluation and the gastric study; and 300mg/kg was used in the toxicokinetic study. No impact from the dose of 300mg/kg could be identified; while, one animal died at 2000mg/kg in the acute toxicity test. In the subchronic toxicity test, changes in the biochemical parameters of the liver, as well as in the histopatological evaluation, demonstrated that BS is a hepatotoxic drug. BS proved to be effective for moderate and severe gastric lesions. In the toxicokinetics study, BS presented a low concentration and rapid plasma disappearance. Several results also indicate that BS is likely to be mostly eliminated from the liver and may well undergo a first-pass effect after oral absorption. It was impossible to estimate the noobserved-adverse-effect-levels (NOAEL) and lowest-observed-adverse-effect-levels (LOAEL) due to the presence of hepatotoxicity in all tested doses.

Gastroprotective and toxicological evaluation of the Lithothamnion calcareum algae.

Lithothamnion calcareum is a red alga of the Corallinacea family whose main feature is the formation of calcium carbonate precipitate in its cell walls. L. calcareum is marketed as a nutritional supplement for calcium and other minerals in Brazil and other countries under the pharmaceutical name of Vitality 50+. In this study, gastroprotective and pre-clinical toxicity assays were performed on this product. Doses of 30, 120 and 480 mg/kg were used in the gastroprotective study on Wistar rats. A dose of 2000 mg/kg was used in the preclinical acute toxicity study and oral doses of 1000 and 2000 mg/kg were used in the subchronic toxicity evaluation. L. calcareum played no significant role in the protection of the rats' gastric mucosa, nor did it cause increase in gastric irritation. No impact on the acute toxicity test was identified. In the subchronic toxicity test, serum levels of albumin, total protein and calcium decreased, and creatinine levels increased, suggesting hypercalcemia and possible kidney damage associated with liver damage, given that the majority of these parameters were irreversible. Thus, this work aims to discuss the relationship of the high concentration of calcium in the product with the observed effects.

Campomanesia lineatifolia Ruiz & Pav. as a gastroprotective agent.

ETHNOPHARMACOLOGICAL RELEVANCE: Campomanesia lineatifolia Ruiz and Pav. (Myrtaceae) is a native edible species found in the Amazon Rainforest, commonly known as gabiroba. In Brazil, Campomanesia species are frequently used in traditional medicine for gastrointestinal disorders. MATERIALS AND METHODS: The present study performed phytochemical analyses and determined both the in vitro antioxidant activity of the ethanolic extract of Campomanesia lineatifolia leaves (EEC) as well as its ethyl acetate fraction (EAFC). In this analysis, quercetin was used as a positive control. Gastroprotective activity was also investigated at different oral doses in two experimental models in rats - gastric lesion induced by ethanol and gastric lesion induced by indomethacin. In this analysis, cimetidine and sucralfate were used as positive controls. The area of gastric lesion underwent macroscopic and histomorphometric evaluations, while the mucus content was estimated by applying the periodic acid-Schiff stain. Oral acute toxicity was also assessed. RESULTS: Phytochemical studies revealed the presence of flavonoids and tannins. Catechin and quercitrin were isolated by bioguided chromatographic fractionation of EAFC. EEC and EAFC presented in vitro antioxidant activity. The oral administration of EEC and EAFC at doses 100-400 mg/kg (ethanol model) and at doses of 400-1200 mg/kg (indomethacin model) proved to be effective in preventing gastric ulcerations in rats. Pretreatment with EAFC (400mg/kg) significantly increased the gastric mucus content in the ethanol model. No animals died during the acute oral toxicology test. CONCLUSIONS: Results confirm the Brazilian ethnopharmacological use of Campomanesia lineatifolia as a gastroprotective agent and indicate that the anti-ulcer effect is most likely mediated by scavenging free radicals due to the polyphenol content and, at least in part, by increasing the mucus secretion and the mucosal defense. In addition, EEC and EAFC were found to be safe when applied to a 2000 mg/kg single oral dose.

Cadmium- and lead-induced apoptosis in mallard erythrocytes (Anas platyrhynchos).

Cadmium, lead and cadmium-lead (1:10) induced apoptosis were studied using mallard blood cells. The allowable range in concentrations were: 0.01-0.5, 0.1-5.0, and 0.01:0.10-0.50:5.00 mM, for cadmium, lead and cadmium-lead, respectively. The lowest EC(50) achieved was for cadmium (0.22+/-0.04 mM). Two doses from each treatment group were chosen to study apoptosis and the presence of metals in cells. The percentage of apoptotic cells increased as the concentration of metals increased. The percentage of cells with intracellular metals was high for both exposure levels and the quantity of intracellular metal was greater for exposure to high concentrations. Morphological alterations for all types of exposure were related to the diverse range of effects that these metals have on membranes. We suggest that the decrease in the number of erythrocytes observed in specimens suffering from lead and cadmium poisoning is related to the induction of apoptosis.

Acute and chronic toxicological studies of Dimorphandra mollis in experimental animals.

Dimorphandra mollis Benth. (Caesalpiniaceae), known as "faveira" or "fava d'anta" is a common plant in central Brazilian cerrado that is used mainly as a vasoprotector. Its main marker is rutin. The present study aimed to evaluate the security of Dimorphandra mollis dry extract in rodents. The extract presented a rutin content of 76+/-3%. Acute and chronic (180 days) toxicity was evaluated after per os administration. In acute toxicity, 3500 and 5000 mg/kg doses presented reversible effects. In chronic toxicity, 1000 and 2000 mg/kg doses did not provoke significant changes in body weight of the animals and in water and food consumption. Behavioral reversible changes and in blood count parameters (hemoglobin, hematocrit and red cells decrease and platelets increase in male in rats) were observed only in 2000 mg/kg dose. In biochemical evaluation, the results varied a lot considering doses and sex, without a linear profile. Some parameters showed a significant difference but without a clinical correlation. In histopathological examination, lung hemorrhage was observed in 2000 mg/kg dose. In conclusion, the study suggest that the extract is safe in a 1000 mg/kg dose, whereas for 2000 mg/kg dose further studies are needed. In long-term use, caution is required.

Avaliação da atividade antiulcerogênica da Maytenus truncata Reiss (Celastraceae) / Evaluation of antiulcerogenic activity of Maytenus truncata Reiss (Celastraceae)

Maytenus truncata Reiss (Celastraceae) é uma planta nativa da Bahia (Brasil), sendo conhecida como "espinheira-santa". É usada popularmente na forma de decoto das folhas (chás) como antiulcerogênico, similarmente à Maytenus ilicifolia, a verdadeira "espinheira-santa". O objetivo do presente estudo foi avaliar a atividade antiúlcera e cicatrizante, assim como o perfil fitoquímico dos extratos brutos em acetato de etila e metanol da Maytenus truncata. A administração per os desses extratos nas doses de 120 mg/kg e 240 mg/kg reduziu a severidade da lesão gástrica induzida pelo estresse ao frio (-18 °C por 45 minutos) em ratos, com resultados mais significativos para o extrato bruto obtido em metanol. A administração dos extratos provocou o aumento do pH. Os resultados obtidos na administração do extrato bruto em metanol não contrariam seu uso popular, não somente pela atividade observada, mas também por se tratar de um extrato de alta polaridade cujos princípios podem ser obtidos a partir de uma infusão, embora estudos clínicos devam ser realizados para confirmação dessa hipótese.

Maytenus truncata Reiss (Celastraceae) is a native plant from Bahia (Brazil), known as "espinheira-santa". It is popularly used in the form of decoct of leaves (tea) as antiulcerogenic, similarly to Maytenus ilicifolia, the true "espinheira-santa". This study aims to evaluate antiulcerogenic and healing activities, as well as the phytochemical profile, of ethyl acetate and methanol crude extracts of Maytenus truncata. Per os administration of these extracts at 120 mg/kg and 240 mg/kg doses decreased the severity of gastric lesions induced by cold-restraint stress (-18 °C for 45 minutes) in rats, with more significant results for the crude methanol extract. The administration of the extracts caused pH increase. The results obtained with the administration of crude methanol extract are not contrary to its popular use, not only for the activity observed but, also, for its high polarity that enables the obtention of the active principles through infusion, though clinical studies should be performed to confirm this assertion.

Anti-inflammatory, antinociceptive and ulcerogenic activity of a zinc-diclofenac complex in rats

We investigated the anti-inflammatory, antinociceptive and ulcerogenic activity of a zinc-diclofenac complex (5.5 or 11 mg/kg) in male Wistar rats (180-300 g, N = 6) and compared it to free diclofenac (5 or 10 mg/kg) and to the combination of diclofenac (5 or 10 mg/kg) and zinc acetate (1.68 or 3.5 mg/kg). The carrageenin-induced paw edema and the cotton pellet-induced granulomatous tissue formation models were used to assess the anti-inflammatory activity, and the Hargreaves model of thermal hyperalgesia was used to assess the antinociceptive activity. To investigate the effect of orally or intraperitoneally (ip) administered drugs on cold-induced gastric lesions, single doses were administered before exposing the animals to a freezer (-18ºC) for 45 min in individual cages. We also evaluated the gastric lesions induced by multiple doses of the drugs. Diclofenac plus zinc complex had the same anti-inflammatory and antinociceptive effects as diclofenac alone. Gastric lesions induced by a single dose administered per os and ip were reduced in the group treated with zinc-diclofenac when compared to the groups treated with free diclofenac or diclofenac plus zinc acetate. In the multiple dose treatment, the complex induced a lower number of the most severe lesions when compared to free diclofenac and diclofenac plus zinc acetate. In conclusion, the present study demonstrates that the zinc-diclofenac complex may represent an important therapeutic alternative for the treatment of rheumatic and inflammatory conditions, as its use may be associated with a reduced incidence of gastric lesions.

Anti-inflammatory, antinociceptive and ulcerogenic activity of a zinc-diclofenac complex in rats.

We investigated the anti-inflammatory, antinociceptive and ulcerogenic activity of a zinc-diclofenac complex (5.5 or 11 mg/kg) in male Wistar rats (180-300 g, N = 6) and compared it to free diclofenac (5 or 10 mg/kg) and to the combination of diclofenac (5 or 10 mg/kg) and zinc acetate (1.68 or 3.5 mg/kg). The carrageenin-induced paw edema and the cotton pellet-induced granulomatous tissue formation models were used to assess the anti-inflammatory activity, and the Hargreaves model of thermal hyperalgesia was used to assess the antinociceptive activity. To investigate the effect of orally or intraperitoneally (ip) administered drugs on cold-induced gastric lesions, single doses were administered before exposing the animals to a freezer (-18 degrees C) for 45 min in individual cages. We also evaluated the gastric lesions induced by multiple doses of the drugs. Diclofenac plus zinc complex had the same anti-inflammatory and antinociceptive effects as diclofenac alone. Gastric lesions induced by a single dose administered per os and ip were reduced in the group treated with zinc-diclofenac when compared to the groups treated with free diclofenac or diclofenac plus zinc acetate. In the multiple dose treatment, the complex induced a lower number of the most severe lesions when compared to free diclofenac and diclofenac plus zinc acetate. In conclusion, the present study demonstrates that the zinc-diclofenac complex may represent an important therapeutic alternative for the treatment of rheumatic and inflammatory conditions, as its use may be associated with a reduced incidence of gastric lesions.

Evaluation of antinociceptive, anti-inflammatory and antiulcerogenic activities of Maytenus ilicifolia.

Maytenus ilicifolia (Celastraceae) is a native plant from Tropical Atlantic Forest (Mata Atlântica, Brazil) called 'espinheira-santa'. This plant is traditionally used as anti-inflammatory, analgesic and antiulcerogenic. Many studies focusing pharmacological and toxicological aspects of the plant have been performed. The aim of this study is to evaluate the efficacy (anti-inflammatory and antinociceptive activities and protection against gastric lesions, including cytoprotection and healing) and phytochemical profile of hexane and ethylacetate extracts of Maytenus ilicifolia. Per os administration of these extracts inhibited nociception and formaldehyde-induced paw oedema in mice and carrageenin-induced paw oedema in rats. Severity of gastric lesions induced by cold-restraint stress (-18 degrees C for 45 min) method was also clearly reduced in rats considering both cytoprotection and healing aspects. Administration of the extracts led to volume gastric and pH increase. These results suggest that hexane and ethylacetate extracts of Maytenus ilicifolia may represent an important clinical alternative in anti-inflammatory and antiulcerogenic therapeutics, though, further experiments should be performed to confirm this assertion.

Pharmacokinetic profile and adverse gastric effect of zinc-piroxicam in rats.

Complexation of piroxicam with zinc extends its absorption time in rats. The time of peak concentration value for complexed piroxicam was 5.27 hr compared to only 2.56 hr for the uncomplexed agent. Piroxicam and zinc-piroxicam show similar inhibitory effects on carrageenin-induced paw edema. Zinc-piroxicam is less irritating than piroxicam on the gastric mucosa.

Identificação de atenolol e metoprolol em urina por cromatografia gasosa / Urine atenolol and metoprolol identification by gaseous cromatography

Os bloqueadores beta-adrenérgicos(BBA), atenolol e metoprolol são agentes largamente utilizados no tratamento de doenças cardiovasculares como hipertensão, arritmias e angina. No entanto, nos últimos anos, tem sido relatado seu uso para outras finalidades, além da terapêutica, como em superdose intencional para cometer o suicidio e como agente de dopagem em esportes onde o tremor e o estresse podem prejudicar a performance do atleta. Para análise dos BBA em material biológico, tem sido desenvolvidas várias técnicas nos últimos anos. Na análises de pequenas concentrações (ng/ml) tem sido empregado o CG-EM. Esta técnica é muito onerosa. O método que utiliza cromatografia gasosa como detector por captura de elétrons (DCE) tem mostrado sensibilidade adequada para detecção dos BBA, além de ter maior uso em nosso país. A finalidade deste trabalho foi desenvolver um método que permita identificação de pequenas concentrações desses BBA em urina em urina por DCE usando coluna empacotada. Os limites de detecção foram 75 e 55 ng/ml para atenolol e metoprolol, respectivamente. O método desenvolvido permite a identificação de BBA em urina de voluntários após dose única e subterapêutica de atenolol e metoprolol.