Comparison of the up-and-down method and the fixed-dose procedure for acute oral toxicity testing

Network pharmacology combined with transcriptomics reveals that Ganoderma lucidum spore and Sanghuangporus vaninii compound extract exerts anti-colorectal cancer effects via CYP24A1-mediated VDR pathway and TERT-mediated Wnt signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

As traditional medicinal fungi, Ganoderma lucidum and Sanghuangporus vaninii are widely used in the treatment of tumor related diseases and cancer adjuvant therapy with potent anticancer effects. However, the anticancer effect and mechanism of action of their compound extract remain unclear.

AIM OF THE STUDY

To investigate the anticancer effect of Ganoderma lucidum and Sanghuangporus vaninii compound extract and explore the underlying mechanism.

MATERIALS AND METHODS

First, MTT assay was performed to investigate the effect of 8 different extracts on tumor cell viability. Moreover, the synergistic effect of Ganoderma lucidum spore and Sanghuangporus vaninii was evaluated by Chou-Talalay method. Subsequently, the fractional extractions were conducted to further isolate anti-tumor active components. Next, network pharmacology combined with transcriptomics was used to explore the potential mechanisms underlying the anticancer effect of compound extract. Finally, the mechanism of action was verified using in vitro and in vivo models.

RESULTS

Among all 8 extracts, Ganoderma lucidum spore and Sanghuangporus vaninii compound ethanol extract (GSEE) showed the most significant cell viability inhibitory effect on cancer cells, especially colorectal cancer (CRC) cells, which was even better than combination of Sanghuangporus vaninii ethanol extract (SVEE) and Ganoderma lucidum spore ethanol extract (GLEE). The ethyl acetate fraction of GSEE (GSEAE) was screened as the anti-tumor active fraction of GSEE and could suppress CRC proliferation in vitro and in vivo. The CYP24A1-mediated Vitamin D receptor (VDR) pathway and TERT-mediated Wnt signaling pathway were identified as the main mechanisms of GSEAE against CRC. Multiple CRC models confirmed that GSEAE suppressed CRC metastasis, arrested cell cycle and induced mitochondrial apoptosis of CRC cells via VDR pathway and Wnt signaling pathway.

CONCLUSIONS

Collectively, our data suggest that compound extract GSEAE exerts anti-CRC effects via CYP24A1-mediated VDR pathway and TERT-mediated Wnt signaling pathway.

Dexmedetomidine decreases the 50% effective dose (ED50) of intravenous propofol required to prevent tracheal intubation response in Beagles

OBJECTIVE

To determine the 50% effective dose (ED50) of intravenous propofol required for successfully preventing tracheal intubation response in Beagles co-induced with dexmedetomidine.

ANIMALS

36 adult male Beagles.

PROCEDURES

The dogs were randomly assigned to either group D1, group D2, or group C (received 1 µg/kg, 2 µg/kg dexmedetomidine intravenously, or the same amount of normal saline as dexmedetomidine, 10 mL). The first dog in each group received 6 mg/kg of propofol for induction. The pump speed of propofol was 600 mL/h. The dosage varied with increments or decrements of 0.5 mg/kg based on the Dixon up-and-down method. The duration of eye-opening after propofol administration was recorded. Changes in heart rate (HR) and respiratory rate (RR) were recorded at 5 timepoints: after entering the operation room and prior to propofol administration (T1), 1 and 3 min after propofol administration (T2 and T3), 3 and 5 min after intubation (T4 and T5).

RESULTS

The required ED50 of propofol that prevented tracheal intubation response in D1, D2, and C groups were 6.4 mg/kg (95% CI, 6.1 to 6.7 mg/kg), 5.8 mg/kg (95% CI, 5.67 to 6 mg/kg), and 8.3 mg/kg (95% CI, 8 to 8.5 mg/kg), respectively. The recovery time of group D2 was significantly longer than that of groups D1 and C (P < .05). The differences in HR among the 3 groups were significant from T2 up to T5 timepoint (P < .05). The differences in RR among the 3 groups were significant at T2 and T3 timepoints (P < .05).

CLINICAL RELEVANCE

Dexmedetomidine pre-injection reduces the amount of propofol required for endotracheal intubation response in Beagles, thereby reducing the respiratory inhibition induced by propofol.

Novel cytotoxicity test based on menadione-catalyzed H2O2 productivity for food safety evaluation

Menadione-catalyzed H(2)O(2) production by viable cells was proportional to viable cell number, and the assay of this H(2)O(2) production was applied to the cytotoxicity test of 17 substances which were used for international validation of fixed-dose procedure as an alternative to the classical LD(50) test. The cytotoxicity of substances tested was observed 4 h after the incubation with animal cells, and the viability was determined in 10 min according to menadione-catalyzed H(2)O(2) production assay. IC(50) of each substance required for 50% inhibition of menadione-catalyzed H(2)O(2) production was similar among HepG2, HuH-6KK, HUVE, Vero, Intestine407, NIH/3T3 and Neuro-2a cells. Twelve substances, 3 substances and 2 substances showed the difference of one, two and three orders in the magnitude between LD(50) and IC(50), respectively. These results show that menadione-catalyzed H(2)O(2) production assay is useful for the rapid detection of toxic compounds having the basal cytotoxicity common to various cells, but is unfit for the detection of organ-specific toxic compounds.

Biocompatibility of bacterial magnetosomes: acute toxicity, immunotoxicity and cytotoxicity

In this study, we examined the acute toxicity, immunotoxicity, and cytotoxicity of bacterial magnetosomes (BMs). LD(50) of BMs injected into the sublingual vein of SD rats was 62.7 mg/kg. Further studies with injection of 40 mg/kg BMs showed no significant difference between BM-treated and control rats in terms of routine blood exam results, liver and kidney function tests, organ coefficients of major organs, or Stimulation Index (SI) of lymph cells with ConA and/or LPS antigens. Histological examination of major organs from 40 mg/kg BM-treated rats showed no obvious pathological changes except for increased number of vacuoles in livers, and somewhat thicker interlobular septa in lungs. BMs showed little cytotoxic effect on H22, HL60, or EMT-6 cells. Growth of all three cells was neither inhibited nor stimulated by incubation with 9 microg/ml BMs, which also had no effect on DNA content, cell size, or cell membrane integrity.

Acute toxicity profile of maprotiline in the rat

The aim of the present study was to examine the toxic effects of single oral administrations of the antidepressant maprotiline at 150 mg/kg or 300 mg/kg using female Sprague-Dawley rats. Body-weight gain was significantly reduced in the group receiving 300 mg/kg on days 1-5 of the study (P<0.01). A significant reduction in food and water intake was observed on days 1 and 2 of the study (P<0.01) in the 300 mg/kg group and on day 1 in the 150 mg/kg group (P<0.05). There was a significant decrease in nocturnal home cage activity over the first five days of the study in the 300 mg/kg group (P<0.01). A significant hypothermic response was observed in both 150 and 300 mg/kg groups at 1, 2 and 4 hr after dosing (P<0.01), that had returned to control values within 8 hr following administration. This study demonstrates that a multi-parameter approach is appropriate for the investigation of high doses of antidepressants in rodents.

Acute oral toxicity

The purposes of acute toxicity testing are to obtain information on the biologic activity of a chemical and gain insight into its mechanism of action. The information on acute systemic toxicity generated by the test is used in hazard identification and risk management in the context of production, handling, and use of chemicals. The LD50 value, defined as the statistically derived dose that, when administered in an acute toxicity test, is expected to cause death in 50% of the treated animals in a given period, is currently the basis for toxicologic classification of chemicals. For a classical LD50 study, laboratory mice and rats are the species typically selected. Often both sexes must be used for regulatory purposes. When oral administration is combined with parenteral, information on the bioavailability of the tested compound is obtained. The result of the extensive discussions on the significance of the LD50 value and the concomitant development of alternative procedures is that authorities today do not usually demand classical LD50 tests involving a large number of animals. The limit test, the fixed-dose procedure, the toxic class method, and the up-and-down methods all represent simplified alternatives using only a few animals. Efforts have also been made to develop in vitro systems; e.g., it has been suggested that acute systemic toxicity can be broken down into a number of biokinetic, cellular, and molecular elements, each of which can be identified and quantified in appropriate models. The various elements may then be used in different combinations to model large numbers of toxic events to predict hazard and classify compounds.

Comparison of the up-and-down, conventional LD50, and fixed-dose acute toxicity procedures

The up-and-down procedure (UDP), fixed-dose procedure (FDP) and conventional LD50 tests were compared to determine their consistency in chemical hazard classification for acute oral toxicity according to the European Economic Community (EEC) system. There was consistent classification for 23 out of 25 cases between the UDP and the conventional LD50 results, in 16 out of 20 cases between the FDP and the conventional LD50, and in seven out of 10 cases between the UDP and the FDP. The UDP needed only between six and 10 animals of one sex (fewer than either the LD50 or the FDP). Available literature indicates that the sexes are usually similar in their acute toxicity responses and that of females are often more sensitive than males when acute toxicity differences do exist, thus obviating the need for both sexes to be tested in most cases. Unlike the FDP, the UDP also estimates an LD50, thus providing data directly applicable to all current hazard classification systems based on acute oral toxicity.