Assessment of the mutagenic, recombinagenic and carcinogenic potential of orlistat in somatic cells of Drosophila melanogaster

Exploration of Teratogenic and Genotoxic Effects on Model Organism Drosophila melanogaster

Drosophila melanogaster is one of the crucial in vivo models in terms of analyzing the toxicity of various unknown chemicals. Every part of the fly serves as a model in metabolic and therapeutic approaches. Genotoxic and teratogenic compounds are exposed to Drosophila through the oral route. Further, the toxicity of genotoxic compounds is analyzed in Drosophila's gut, hemolymph, and phenotype. The toxicity of teratogen compounds is also analyzed using a Drosophila embryo. The current chapter summarizes several techniques that are used to detect the genotoxicity and teratogenicity of any unknown compound in this model.

Potential implications of vouacapan compounds for insecticidal activity: an in silico study

BACKGROUND

From the fruits and seeds of the species of Pterodon, it is possible to obtain two main products: the essential oil and oleoresin. In oleoresin, numerous vouacapan compounds have been demonstrated to have biological potential, including insecticidal activity.

OBJECTIVE

In silico studies were performed to identify potential candidates for natural insecticides among the vouacapans present in the genus Pterodon.

MATERIALS AND METHODS

Molecular docking and molecular dynamics studies were performed to analyze the interaction of vouacapan compounds with acetylcholinesterase of Drosophila melanogaster. Pharmacokinetic parameters regarding physicochemical properties, plasma protein binding, and activity in the central nervous system were evaluated. The toxicological properties of the selected molecules were predicted using Malathion as the reference compound.

RESULTS

6α,7β-dimethoxivouacapan-17-ene (15) showed a high number of interactions and scores in molecular docking studies. This result suggests that this compound exhibits an inhibitory activity of the enzyme acetylcholinesterase. Regarding physicochemical properties, this compound showed the best results, besides presenting low cutaneous permeability values, suggesting null absorption. Molecular dynamics studies demonstrated few conformational changes in the structure of the complex formed by compound 4 and acetylcholinesterase enzyme throughout the simulation time.

CONCLUSION

It was determined that compound 4 (vouacapan 6α,7β,17β,19-tetraol) is an excellent candidate for usage as a natural insecticide.

Modulating effect of DL-kavain on the mutagenicity and carcinogenicity induced by doxorubicin in Drosophila melanogaster

Kavain, kavalactone, present in Piper methysticum exhibits anticonvulsive, analgesic, anxiolytic, antiepileptic, antithrombotic, anti-inflammatory and antioxidant properties. Given its importance, the aim of the present study was to assess (1) the mutagenic and carcinogenicity of kavain administered alone and (2) the antimutagenic and anticarcinogenic potential when administered simultaneously with the chemotherapeutic drug doxorubicin (DXR) using the Somatic Mutation and Recombination Test (SMART) and Epithelial Tumor Test (ETT) using Drosophila melanogaster as a model system. Third-stage larvae from a standard (ST) and high metabolic bioactivation (HB) crosses were treated with different kavain concentrations (32, 64 or 128 μg/ml), alone or in conjunction with DXR (0.125 mg/ml). In ST descendants, kavain produced no significant mutagenic or recombinogenic effects. In the HB cross, mutagenic activity was observed at kavain concentrations of 64 and 128 μg/ml. In the DXR and kavain co-treatment, a modulating effect of the DXR-mediated mutagenic response dependent upon the concentration was detected in both crosses. In ETT, no marked carcinogenic or anticarcinogenic activity was noted for kavain. However, when kavain was combined with DXR synergistic induction of tumors by the chemotherapeutic drug occurred indicating that kavain enhanced the carcinogenic action of DXR.

Modulating effect of vitamin D3 on the mutagenicity and carcinogenicity of doxorubicin in Drosophila melanogaster and in silico studies

Vitamin D3 (VD3) deficiency increases DNA damage, while supplementation may exert a pro-oxidant activity, prevent viral infections and formation of tumors. The aim of this study was to investigate the mutagenicity and carcinogenicity of VD3 alone or in combination with doxorubicin (DXR) using the Somatic Mutation and Recombination Test and the Epithelial Tumor Test, both in Drosophila melanogaster. For better understanding of the molecular interactions of VD3 and receptors, in silico analysis were performed with molecular docking associated with molecular dynamics. Findings revealed that VD3 alone did not increase the frequency of mutant spots, but reduced the frequency of mutant spots when co-administered with DXR. In addition, VD3 did not alter the recombinogenic effect of DXR in both ST and HB crosses. VD3 alone did not increase the total frequency of tumor, but significantly reduced the total frequency of tumor when co-administered with DXR. Molecular modeling and molecular dynamics between calcitriol and Ecdysone Receptor (EcR) showed a stable interaction, indicating the possibility of signal transduction between VD3 and EcR. In conclusion, under these experimental conditions, VD3 has modulatory effects on the mutagenicity and carcinogenicity induced by DXR in somatic cells of D. melanogaster and exhibited satisfactory interactions with the EcR.

Genotoxicity and carcinogenicity of ivermectin and amoxicillin in vivo systems

Antiparasitic substances are chemicals used to control or kill endoparasites and ectoparasites. Based on the premise that Ivermectin (IVM) and Amoxicillin (AMX) are commonly considered in parasitic control in mammals, the present study aimed to evaluate the carcinogenic and genotoxic potential of different concentrations of IVM and AMX through the detection of epithelial tumor test in Drosophila melanogaster. Third-instar larvae descending from the cross between wts/TM3, Sb¹ females and mwh/mwh males were treated with different concentrations of IVM (2.9, 5.8, 11.6 and 23.2 x 10^-17 mM) or AMX (1.37, 2.74, 5.48 and 10.9 x 10^-16mM). The results revealed that IVM increased the frequency of epithelial tumor in D. melanogaster considering all evaluated concentrations, while AMX showed no carcinogenic effect. Furthermore, the Micronucleus (MN) test in Tradescantia pallida was used to evaluate the genotoxic effect of IVM and AMX. T. pallida individuals were exposed for 8 hours at different concentrations of IVM (5.71, 11.42, 22.84 and 45.68 x 10^-5mM) or AMX (5.13, 10.26, 20.52 and 41.05 x 10^-3mM). Findings showed an increase in the frequency of micronuclei in T. pallida treated with 11.42, 22.84 and 45.68 x 10^-5mM of IVM. We conclude that chronic exposure to IVM is directly associated with events resulting from genetic instability (genotoxicity and carcinogenicity). On the other hand, AMX was neither carcinogenic nor genotoxic for D. melanogaster and T. pallida.

Protective effect of aspirin against mitomycin C-induced carcinogenicity, assessed by the test for detection of epithelial tumor clones (warts) in Drosophila melanogaster

The present study assessed the protective effect of aspirin against carcinogenicity induced by mitomycin C (MMC) by the test for detection of warts/epithelial tumor clones in Drosophila melanogaster. Larvae were treated with different concentrations of aspirin alone (10, 20 or 40 mg/mL) or aspirin in association with MMC. MMC and ultrapure water were employed as the positive and negative control, respectively. Antioxidant activity was determined using the DPPH method. For performing cytotoxicity assay on HeLa cells, the aspirin concentrations used ranged from 200 mmol/L to 3,125 mmol/L. For assessment of apoptosis and necrosis, cells were incubated for 24 h with complete medium in the absence (control group) or presence of aspirin (12.5 mmol/L and 25 mmol/L). The results obtained in the assessment of the possible carcinogenic effects of aspirin at the three concentrations tested indicate no statistically significant increase in tumor frequency compared to the negative control. The anticarcinogenic activity assessment, where the larvae of D. melanogaster were previously induced to tumor formation by MMC and later treated with aspirin, showed a statistically significant reduction in the number of tumors compared to the positive control. Antioxidant activity across the three aspirin concentrations (10, 20 or 40 mg/mL) ranged from 20.81% to 26.5%. It was observed that aspirin reduced growth viability of HeLa cells in a concentration-dependent manner in comparison with the control. These results indicate that aspirin did not induce tumors in Drosophila and reduced MMC-induced carcinogenicity. The antioxidant activity and apoptosis induction appear to be the main mechanisms involved in reducing the frequency of tumors.

Chylomicrons stimulate incretin secretion in mouse and human cells

AIMS/HYPOTHESIS

Lipids are a potent stimulus for the secretion of glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic peptide (GIP). Traditionally, this effect was thought to involve the sensing of lipid digestion products by free fatty acid receptor 1 (FFA1) and G-protein coupled receptor 119 (GPR119) on the apical surface of enteroendocrine cells. However, recent evidence suggests that lipids may in fact be sensed basolaterally, and that fatty acid absorption and chylomicron synthesis may be a prerequisite for their stimulatory effect on gut peptide release. Therefore, we investigated the effect of chylomicrons on GLP-1 and GIP secretion in vitro.

METHODS

The effect of chylomicrons on incretin secretion was investigated using GLUTag cells and duodenal cultures of both murine and human origin. The role of lipoprotein lipase (LPL) and FFA1 in GLUTag cells was assessed by pharmacological inhibition and small (short) interfering RNA (siRNA)-mediated knockdown. The effect of chylomicrons on intracellular calcium concentration ([Ca²⁺]_i) was determined by imaging GLUTag cells loaded with Fura-2. In the primary setting, the contributions of FFA1 and GPR119 were investigated using L cell-specific Gpr119 knockout cultures treated with the FFA1 antagonist GW1100.

RESULTS

Chylomicrons stimulated GLP-1 release from GLUTag cells, and both GLP-1 and GIP secretion from human and murine duodenal cultures. Chylomicron-triggered GLP-1 secretion from GLUTag cells was largely abolished following lipase inhibition with orlistat or siRNA-mediated knockdown of Lpl. In GLUTag cells, both GW1100 and siRNA-mediated Ffar1 knockdown reduced GLP-1 secretion in response to chylomicrons, and, consistent with FFA1 G_q-coupling, chylomicrons triggered an increase in [Ca²⁺]_i. However, LPL and FFA1 inhibition had no significant effect on chylomicron-mediated incretin secretion in murine cultures. Furthermore, the loss of GPR119 had no impact on GLP-1 secretion in response to chylomicrons, even in the presence of GW1100.

CONCLUSIONS/INTERPRETATION

Chylomicrons stimulate incretin hormone secretion from GLUTag cells as well as from human and murine duodenal cultures. In GLUTag cells, the molecular pathway was found to involve LPL-mediated lipolysis, leading to the release of lipid species that activated FFA1 and elevated intracellular calcium.

Mutagenic, recombinogenic and carcinogenic potential of thiamethoxam insecticide and formulated product in somatic cells of Drosophila melanogaster

Thiamethoxam (TMX) belongs to a class of neuro-active insecticides referred as neonicotinoids, while actara^® (AC) is one of the most popular TMX-based products in Brazil. The aim of this study was to evaluate the mutagenic, recombinogenic and carcinogenic potential of TMX and AC insecticides. The mutagenic and recombinogenic effect of TMX and AC were evaluated in vivo by the Somatic Mutation and Recombination Test (SMART) while carcinogenic effects were evaluated through the Test for Detection of Epithelial Tumor Clones (wts test), both in somatic cells of Drosophila melanogaster. In the SMART, third instar larvae from standard (ST) and high bioactivation (HB) crosses were treated with different concentrations of TMX and AC (2.4; 4.8; 9.7 × 10^-4 mM and 1.9 × 10^-3 mM). The results revealed mutagenic effects at the highest concentrations tested in the HB cross. In the test for the detection of epithelial tumor, third instar larvae resulting from the cross between wts/TM3, Sb¹ virgin females and mwh/mwh males were treated with the same concentrations of TMX and AC used in the SMART. No carcinogenic effect was observed at any of the concentrations tested. In this work, the inhibition of the mechanism of repair by homologous recombination was observed in flies exposed to 9.7 × 10^-4 and 1.9 × 10^-3 mM of AC. In conclusion, TMX and AC demonstrated to be a promutagen in the highest concentrations tested.

Assessment of the mutagenic, recombinogenic, and carcinogenic potential of amphotericin B in somatic cells of Drosophila melanogaster

Amphotericin B (AmB) is an antifungal antibiotic extracted from Streptomyces nodosus. Its fungicidal activity depends primarily on its binding to the sterol group that is present in fungal membranes. In view of the toxicity of this drug, the purpose of this study was to evaluate its mutagenic, carcinogenic, and recombinogenic activity, based on the wing somatic mutation and recombination test (SMART) and the epithelial tumor detection test (wts) applied to Drosophila melanogaster. Larvae were chronically treated with different concentrations of AmB (0.01, 0.02, and 0.04 mg/mL). The results revealed that AmB is a promutagen exhibiting increase in the number of spots on individuals from high bioactivation (HB) cross with a high level of cytochrome P450. The results also indicate that the main genotoxic event induced by AmB is recombinogenicity. Homologous recombination can act as a determinant at different stages of carcinogenesis. For verification of carcinogenic potential of this compound, larvae from the wts/mwh and wts/ORR, flr³ were treated with the same three AmB concentrations used in the SMART assay. The results did not provide evidence that AmB has carcinogenic potential in wts/mwh individuals. However, individuals from wts/ORR, flr³ developed tumors at the highest concentration tested.

Genotoxicity of antiobesity drug orlistat and effect of caffeine intervention: an in vitro study

CONTEXT

Obesity is a major global health problem associated with various adverse effects. Pharmacological interventions are often necessary for the management of obesity. Orlistat is an FDA-approved antiobesity drug which is a potent inhibitor of intestinal lipases.

OBJECTIVE

In the current study, orlistat was evaluated for its genotoxic potential in human lymphocyte cells in vitro and was compared with that of another antiobesity drug sibutramine, presently withdrawn from market due its undesirable health effects. Caffeine intake may be an additional burden in people using anorectic drugs, therefore, further work is needed to be carried out to evaluate the possible effects of caffeine on orlistat-induced DNA damage.

MATERIALS AND METHODS

Human lymphocytes were exposed to orlistat (250, 500 and 1000 μg/ml), sibutramine (250, 500 and 1000 μg/ml) and caffeine (25, 50, 75, 100, 125 and 150 μg/ml) to assess their genotoxicity by comet assay in vitro. In addition, lymphocytes were co-incubated with caffeine (50, 75 and 100 μg/ml) and a single concentration of orlistat (250 μg/ml).

RESULTS

Orlistat and sibutramine were genotoxic at all concentrations tested, sibutramine being more genotoxic. Caffeine was found to be genotoxic at concentrations 125 μg/ml and above. Co-treatment of orlistat with non-genotoxic concentrations (50, 75 and 100 μg/ml) of caffeine lead to a decrease in DNA damage.

DISCUSSION AND CONCLUSION

Orlistat can induce DNA damage in human lymphocytes in vitro and caffeine was found to reduce orlistat-induced genotoxicity.

Modulating effect of losartan potassium on the mutagenicity and recombinogenicity of doxorubicin in somatic cells of Drosophila melanogaster

Losartan potassium is an antihypertensive drug in the angiotensin II receptor antagonist (ARA) class. Some studies claim that, in addition to regulating blood pressure, this class of drug has anticancer properties. The objective of this study was to evaluate the genotoxic and antigenotoxic potential of losartan potassium using the SMART (Somatic Mutation and Recombination Test) assay on the somatic cells of Drosophila melanogaster, as well as the possible modulating effects of this drug, when associated with doxorubicin (DXR). Third instar larvae, descendents of standard and high bioactivation (ST and HB) crosses, were chronically treated with different concentrations of losartan potassium (0.25; 0.5; 1; 2; and 4 mM) alone or in association (co-treatment) with doxorubicin (DXR 0.125 mg/mL). The results showed an absence of a mutagenic effect of losartan potassium. In the co-treatment of losartan with DXR, the results showed that losartan is capable of reducing the number of mutant spots induced by DXR without altering the recombinogenic effect of the chemotherapeutic agent. Antiproliferative action appears to be the main mechanism involved in reducing the frequency of mutant spots and consequent modulation of alterations induced by DXR, although this parameter has not been directly assessed in this study.

Influence of fatty acid synthase inhibitor orlistat on the DNA repair enzyme O6-methylguanine-DNA methyltransferase in human normal or malignant cells in vitro

Tetrahydrolipstatin (orlistat), an inhibitor of lipases and fatty acid synthase, is used orally for long-term treatment of obesity. Although the drug possesses striking antitumor activities in vitro against human cancer cells and in vitro and in vivo against animal tumors, it also induces precancerous lesions in rat colon. Therefore, we tested the in vitro effect of orlistat on the expression of O6-methylguanine-DNA methyltransferase (MGMT), a DNA repair enzyme that plays an essential role in the control of mutagenesis and carcinogenesis. Western blot analysis demonstrated that 2-day continuous exposure to 40 µM orlistat did not affect MGMT levels in a human melanoma cell line, but downregulated the repair protein by 30-70% in human peripheral blood mononuclear cells, in two leukemia and two colon cancer cell lines. On the other hand, orlistat did not alter noticeably MGMT mRNA expression. Differently from lomeguatrib (a false substrate, strong inhibitor of MGMT) orlistat did not reduce substantially MGMT function after 2-h exposure of target cells to the agent, suggesting that this drug is not a competitive inhibitor of the repair protein. Combined treatment with orlistat and lomeguatrib showed additive reduction of MGMT levels. More importantly, orlistat-mediated downregulation of MGMT protein expression was markedly amplified when the drug was combined with a DNA methylating agent endowed with carcinogenic properties such as temozolomide. In conclusion, even if orlistat is scarcely absorbed by oral route, it is possible that this drug could reduce local MGMT-mediated protection against DNA damage provoked by DNA methylating compounds on gastrointestinal tract epithelial cells, thus favoring chemical carcinogenesis.

Modulating effect of synthetic statins against damage induced by doxorubicin in somatic cells of Drosophila melanogaster

The competitive inhibitors of HMG-CoA reductase, popularly known as statins, exert pleiotropic effects, which result from the ability of statins to inhibit the synthesis of isoprenoids, which are fundamental for the functioning of proteins responsible for intracellular signaling. Some recent studies suggest an important role associated with the use of antineoplastic atorvastatin and rosuvastatin, the statins most widely used today. In this study, the Drosophila wing spot test was used to evaluate possible protective effects of atorvastatin and rosuvastatin against damage induced by DXR. Larvae were chronically treated with negative control (ethanol 5%), positive control (DXR 0.125 mg/mL) and five different concentrations of atorvastatin and rosuvastatin. The results demonstrated absence of a mutagenic effect for the two statins tested. The analysis of the descendants co-treated with DXR and atorvastatin/rosuvastatin revealed a modulatory effect of these statins on damage induced by DXR. This effect was verified in all concentrations tested in the descendants of the ST and HB crosses treated with rosuvastatin, and only in descendants of the HB cross treated with atorvastatin. Induction of apoptosis and antioxidant activity appear to be the main mechanisms involved in reducing the frequency of mutant spots and consequent modulation of the damage induced by DXR.

Recombinogenic activity of Pantoprazole(®) in somatic cells of Drosophila melanogaster

Pantoprazole^® is one of the leading proton pump inhibitors (PPIs) used in the treatment of a variety of diseases related to the upper gastrointestinal tract. However, studies have shown an increased risk of developing gastric cancer, intestinal metaplasia and hyperplasia of endocrine cells with prolonged use. In the present study, the somatic mutation and recombination test (SMART) was employed to determine the mutagenic effects of Pantoprazole on Drosophila melanogaster. Repeated treatments with Pantoprazole were performed on 72-hour larvae of the standard (ST) and high bioactivation (HB) crosses at concentrations of 2.5, 5.0, and 10.0 μM. In addition, doxorubicin (DXR) was administered at 0.4 mM, as a positive control. When administered to ST descendants, total number of spots were statistically significant at 2.5 and 5.0 μM concentrations. For HB descendants, a significant increase in the total number of spots was observed among the marked transheterozygous (MH) flies. Through analysis of balancer heterozygous (BH) descendants, recombinogenic effects were observed at all concentrations in descendants of the HB cross. In view of these experimental conditions and results, it was concluded that Pantoprazole is associated with recombinogenic effects in Drosophila melanogaster.

Lack of mutagenic effect by multi-walled functionalized carbon nanotubes in the somatic cells of Drosophila melanogaster

Carbon nanotubes (CNTs) are formed by rolling up a single graphite sheet into a tube. Among the different types of CNTs, the multi-walled carbon nanotubes (MWCNTs) comprise a set of concentric nanotubes with perfect structures. Several uses for MWCNTs have been suggested to be included in biological applications such as manufacturing of biosensors, carriers of drugs. However, before these materials can be put on the market, it is necessary to know their genotoxic effects. Thus, this study aims to evaluate the mutagenicity of multi-walled carbon nanotubes (MWCNTs) functionalized in somatic cells of Drosophila melanogaster, using the somatic mutation and recombination test (SMART). This assay detects the loss of heterozygosity of marker genes expressed phenotypically on the wings of the fly. Larvae of three days were used, resulting from ST cross, with basal levels of the cytochrome P450 and larvae of high metabolic bioactivity capacity (HB cross). They were treated with different concentrations of MWCNTs functionalized. The MH descendants, analyzed in both ST and HB crosses, had no significant effects on the frequency of mutant. Based on the results and on the experimental conditions mentioned in this study, it was concluded that MWCNTs were not mutagenic in D. melanogaster.