Food preference-based screening method for identification of effectors of substance use disorders using Caenorhabditis elegans

Substance use disorder (SUD) affects over 48 million Americans aged 12 and over. Thus, identifying novel chemicals contributing to SUD will be critical for developing efficient prevention and mitigation strategies. Considering the complexity of the actions and effects of these substances on human behavior, a high-throughput platform using a living organism is ideal. We developed a quick and easy screening assay using Caenorhabditis elegans. C. elegans prefers high-quality food (Escherichia coli HB101) over low-quality food (Bacillus megaterium), with a food preference index of approximately 0.2, defined as the difference in the number of worms at E. coli HB101 and B. megaterium over the total worm number. The food preference index was significantly increased by loperamide, a μ-opioid receptor (MOPR) agonist, and decreased by naloxone, a MOPR antagonist. These changes depended on npr-17, a C. elegans homolog of opioid receptors. In addition, the food preference index was significantly increased by arachidonyl-2'-chloroethylamide, a cannabinoid 1 receptor (CB1R) agonist, and decreased by rimonabant, a CB1R inverse agonist. These changes depended on npr-19, a homolog of CB1R. These results suggest that the conserved opioid and endocannabinoid systems modulate the food preference behaviors of C. elegans. Finally, the humanoid C. elegans strains where npr-17 was replaced with human MOPR and where npr-19 was replaced with human CB1R phenocopied the changes in food preference by the drug treatment. Together, the current results show that this method can be used to rapidly screen the potential effectors of MOPR and CB1R to yield results highly translatable to humans.

Neuronal E93 is required for adaptation to adult metabolism and behavior

OBJECTIVE

Metamorphosis is a transition from growth to reproduction, through which an animal adopts adult behavior and metabolism. Yet the neural mechanisms underlying the switch are unclear. Here we report that neuronal E93, a transcription factor essential for metamorphosis, regulates the adult metabolism, physiology, and behavior in Drosophila melanogaster.

METHODS

To find new neuronal regulators of metabolism, we performed a targeted RNAi-based screen of 70 Drosophila orthologs of the mammalian genes enriched in ventromedial hypothalamus (VMH). Once E93 was identified from the screen, we characterized changes in physiology and behavior when neuronal expression of E93 is knocked down. To identify the neurons where E93 acts, we performed an additional screen targeting subsets of neurons or endocrine cells.

RESULTS

E93 is required to control appetite, metabolism, exercise endurance, and circadian rhythms. The diverse phenotypes caused by pan-neuronal knockdown of E93, including obesity, exercise intolerance and circadian disruption, can all be phenocopied by knockdown of E93 specifically in either GABA or MIP neurons, suggesting these neurons are key sites of E93 action. Knockdown of the Ecdysone Receptor specifically in MIP neurons partially phenocopies the MIP neuron-specific knockdown of E93, suggesting the steroid signal coordinates adult metabolism via E93 and a neuropeptidergic signal. Finally, E93 expression in GABA and MIP neurons also serves as a key switch for the adaptation to adult behavior, as animals with reduced expression of E93 in the two subsets of neurons exhibit reduced reproductive activity.

CONCLUSIONS

Our study reveals that E93 is a new monogenic factor essential for metabolic, physiological, and behavioral adaptation from larval behavior to adult behavior.

[Survey of Helicobacter pylori levofloxacin and clarithromycin resistance rates and drug resistance genes in Ningxia, 2020-2022]

Objective: To explore the rate of Helicobacter pylori (Hp) resistance to levofloxacin and clarithromycin and the common mutation patterns of resistance genes in Ningxia, and to assess the concordance between phenotypic resistance and genotypic resistance. Methods: Cross-sectional study. Patients diagnosed with Hp infection in 14 hospitals in Ningxia region from February 2020 to May 2022 were retrospectively selected. Hp strains were isolated from gastric biopsy specimens of Hp-infected patients and subjected to phenotypic drug sensitivity testing and detection of resistance genes to analyze the rate of Hp resistance to levofloxacin and clarithromycin and the common mutation patterns of resistance genes in Ningxia region; and the concordance rate and Kappa concordance test were used to assess the concordance between phenotypic resistance and genotypic resistance. Results: A total of 1 942 Hp strains were isolated and cultured, and among the infections, 1 069 cases (55.0%) were male and 873 cases (45.0%) were female, aged (50.0±12.5) years (15-86 years). The rates of Hp resistance to levofloxacin and clarithromycin in Ningxia were 42.1% (818/1 942) and 40.1% (779/1 942), respectively, and the rate of dual resistance to both was 22.8% (443/1 942). The rate of resistance to levofloxacin and clarithromycin of Hp strains from female patients was higher than in male patients (levofloxacin: 50.4%(440/873) vs 35.4%(378/1 069); clarithromycin: 44.4%(388/873) vs 36.6%(391/1 069), both P<0.001). Among the GyrA gene mutations associated with levofloxacin resistance, the differences in mutation rate of amino acid at positions 87 and 91 were statistically significant in both drug-resistant and sensitive strains(both P<0.001), except for Asn87Thr. Hp strains were statistically significant for levofloxacin (Kappa=0.834, P<0.001) and clarithromycin (Kappa=0.829, P<0.001) had good concordance in resistance at the phenotypic and genotypic levels. Conclusion: The resistance of Hp to levofloxacin and clarithromycin in Ningxia region is severe, and there is good consistency between genotypic and phenotypic resistance.

Oocyte Quiescence: From Formation to Awakening

Decades of work using various model organisms have resulted in an exciting and emerging field of oocyte maturation. High levels of insulin and active mammalian target of rapamycin signals, indicative of a good nutritional environment, and hormones such as gonadotrophin, indicative of the growth of the organism, work together to control oocyte maturation to ensure that reproduction happens at the right timing under the right conditions. In the wild, animals often face serious challenges to maintain oocyte quiescence under long-term unfavorable conditions in the absence of mates or food. Failure to maintain oocyte quiescence will result in activation of oocytes at the wrong time and thus lead to exhaustion of the oocyte pool and sterility of the organism. In this review, we discuss the shared mechanisms in oocyte quiescence and awakening and a conserved role of noradrenergic signals in maintenance of the quiescent oocyte pool under unfavorable conditions in simple model organisms.

Maintenance of quiescent oocytes by noradrenergic signals

All females adopt an evolutionary conserved reproduction strategy; under unfavorable conditions such as scarcity of food or mates, oocytes remain quiescent. However, the signals to maintain oocyte quiescence are largely unknown. Here, we report that in four different species - Caenorhabditis elegans, Caenorhabditis remanei, Drosophila melanogaster, and Danio rerio - octopamine and norepinephrine play an essential role in maintaining oocyte quiescence. In the absence of mates, the oocytes of Caenorhabditis mutants lacking octopamine signaling fail to remain quiescent, but continue to divide and become polyploid. Upon starvation, the egg chambers of D. melanogaster mutants lacking octopamine signaling fail to remain at the previtellogenic stage, but grow to full-grown egg chambers. Upon starvation, D. rerio lacking norepinephrine fails to maintain a quiescent primordial follicle and activates an excessive number of primordial follicles. Our study reveals an evolutionarily conserved function of the noradrenergic signal in maintaining quiescent oocytes.

Regulation of Satiety Quiescence by Neuropeptide Signaling in Caenorhabditis elegans

Sleep and metabolism are interconnected homeostatic states; the sleep cycle can be entrained by the feeding cycle, and perturbation of the sleep often results in dysregulation in metabolism. However, the neuro-molecular mechanism by which metabolism regulates sleep is not fully understood. We investigated how metabolism and feeding regulate sleep using satiety quiescence behavior as a readout in Caenorhabditis elegans, which shares certain key aspects of postprandial sleep in mammals. From an RNA interference-based screen of two neuropeptide families, RFamide-related peptides (FLPs) and insulin-like peptides (INSs), we identified flp-11, known to regulate other types of sleep-like behaviors in C. elegans, as a gene that plays the most significant role in satiety quiescence. A mutation in flp-11 significantly reduces quiescence, whereas over-expression of the gene enhances it. A genetic analysis shows that FLP-11 acts upstream of the cGMP signaling but downstream of the TGFβ pathway, suggesting that TGFβ released from a pair of head sensory neurons (ASI) activates FLP-11 in an interneuron (RIS). Then, cGMP signaling acting in downstream of RIS neurons induces satiety quiescence. Among the 28 INSs genes screened, ins-1, known to play a significant role in starvation-associated behavior working in AIA is inhibitory to satiety quiescence. Our study suggests that specific combinations of neuropeptides are released, and their signals are integrated in order for an animal to gauge its metabolic state and to control satiety quiescence, a feeding-induced sleep-like state in C. elegans.

[Application of dynamic CT scan in the three-dimensional dynamic morphology changes of laryngeal soft tissue in unilateral vocal fold paralysis patients]

Objective: To explore the dynamic changes of three-dimensional morphology of laryngeal soft tissue and its clinical value in the unilateral vocal fold paralysis (UVFP) patients through dynamic CT scanning during the process from inspiration to phonation. Methods: From October 2017 to July 2019, a retrospective study was performed in 18 patients with UVFP (10 males and 8 females with the range of age from 29 to 75 years old) and 10 normal subjects (5 males and 5 females with the range of age from 25 to 58 years old) in Department of Voice-Otolaryngology Head and Neck Surgery, Section Two, Zhongshan Hospital Xiamen University. The laryngeal dynamic computed tomography (CT) of cine mode was performed. Ten dynamic sequence images of vocal folds movements were obtained during the process from inspiration to phonation. Based on the dynamic changes of glottic area and the displacement of cricoid cartilage. The above dynamic sequence images were divided into inspiratory phase and phonation phase as well as open phase and closed phase. The soft tissue parameters were measured respectively, including vocal folds length, width, thickness and subglottal convergence angle. Independent-sample t test was used to analyze between UVFP group and control group. Results: During the process from inspiration to phonation, the morphology of vocal folds in control group was relatively stable at inspiratory phase and closed phase in phonation. When open phase and closed phase of phonation were switching, the morphology of vocal folds changed obviously. The length of vocal folds became longer (1.19±0.10) mm, the width became wider (2.19±0.17) mm, the thickness became thinner (2.66±0.56) mm, and the subglottal convergence angle decreased (31.45±4.78)°. Compared with the controll group, in the open phase, the thickness and width of the vocal fold on affected side in the UVFP group were thinner (t=10.25, P<0.001) and wider (t=5.25, P<0.001).While in the closed phase, the subglottal convergence angle was larger (t=4.41, P=0.001).The width of the healthy side vocal fold in the UVFP was wider (t=2.54, P=0.026) than that in the control group. The differences in other parameters were not statistically significant. Conclusions: Dynamic laryngeal CT scanning provides a simple and non-invasive method for the objective and quantitative measurement of the dynamic changes of laryngeal morphology from inspiration to phonation. Compared with the control group, the characteristic dynamic changes among UVFP were observed during this particular process, which included changes of subglottal convergence angle and thickness of vocal muscle due to denervation. In addition, in UVFP group, the width of the vocal fold healthy side in the closed phase may be used to assess its compensatory function.

Behavioral States

Caenorhabditis elegans' behavioral states, like those of other animals, are shaped by its immediate environment, its past experiences, and by internal factors. We here review the literature on C. elegans behavioral states and their regulation. We discuss dwelling and roaming, local and global search, mate finding, sleep, and the interaction between internal metabolic states and behavior.

Satiety behavior is regulated by ASI/ASH reciprocal antagonism

Appropriate decision-making is essential for ensuring survival; one such decision is whether to eat. Overall metabolic state and the safety of food are the two factors we examined using C. elegans to ask whether the metabolic state regulates neuronal activities and corresponding feeding behavior. We monitored the activity of sensory neurons that are activated by nutritious (or appetitive) stimuli (ASI) and aversive stimuli (ASH) in starved vs. well-fed worms during stimuli presentation. Starvation reduces ASH activity to aversive stimuli while increasing ASI activity to nutritious stimuli, showing the responsiveness of each neuron is modulated by overall metabolic state. When we monitored satiety quiescence behavior that reflects the overall metabolic state, ablation of ASI and ASH produce the opposite behavior, showing the two neurons interact to control the decision to eat or not. This circuit provides a simple approach to how neurons handle sensory conflict and reach a decision that is translated to behavior.

Regulation of organelle function by metformin

Metformin ameliorates hyperglycemia without the side effects of lactic acidosis or hypoglycemia. Metformin lowers the blood glucose level by decreasing hepatic glucose production in the liver and by increasing glucose uptake in the muscle. Recent studies show that metformin induces cell death in certain cancer cell lines by interfering with the metabolism of the cancer cells. Therefore, understanding the mechanisms of action for metformin will provide insights into how to better treat diabetes and other metabolic disorders and also into the development of new therapeutic drugs. One of the best understood molecular targets of metformin is the mitochondrial complex I. However, given metformin's broad effects on metabolism, it could act on multiple targets. In this review, we summarize current findings in metformin's mechanisms of action regarding its known targets in mitochondria and known effects in cancer cell lines. Then, we introduce endosomal Na⁺ /H⁺ exchangers and the V-ATPase as new potential targets of metformin's action. Finally, we will discuss the hypothesis that metformin directly acts on endosome/lysosome regulation so as to regulate metabolism and ultimately alleviate type 2 diabetes. © 2017 IUBMB Life, 69(7):459-469, 2017.

NHX-5, an Endosomal Na+/H+ Exchanger, Is Associated with Metformin Action

Diabetes is one of the most impactful diseases worldwide. The most commonly prescribed anti-diabetic drug is metformin. In this study, we identified an endosomal Na(+)/H(+) exchanger (NHE) as a new potential target of metformin from an unbiased screen in Caenorhabditis elegans The same NHE homolog also exists in flies, where it too mediates the effects of metformin. Our results suggest that endosomal NHEs could be a metformin target and provide an insight into a novel mechanism of action of metformin on regulating the endocytic cycle.

An opioid-like system regulating feeding behavior in C. elegans

Neuropeptides are essential for the regulation of appetite. Here we show that neuropeptides could regulate feeding in mutants that lack neurotransmission from the motor neurons that stimulate feeding muscles. We identified nlp-24 by an RNAi screen of 115 neuropeptide genes, testing whether they affected growth. NLP-24 peptides have a conserved YGGXX sequence, similar to mammalian opioid neuropeptides. In addition, morphine and naloxone respectively stimulated and inhibited feeding in starved worms, but not in worms lacking NPR-17, which encodes a protein with sequence similarity to opioid receptors. Opioid agonists activated heterologously expressed NPR-17, as did at least one NLP-24 peptide. Worms lacking the ASI neurons, which express npr-17, did not response to naloxone. Thus, we suggest that Caenorhabditis elegans has an endogenous opioid system that acts through NPR-17, and that opioids regulate feeding via ASI neurons. Together, these results suggest C. elegans may be the first genetically tractable invertebrate opioid model.

DOI:http://dx.doi.org/10.7554/eLife.06683.001

When and how much an animal eats is controlled by a complex web of signals that are produced by the animal's body and brain. Molecules called opioid neuropeptides are among these signals, and act to control eating in mammals by binding to receptors in the brain and body. These receptors can also bind to similar molecules called opiates (such as morphine); opiates are amongst the oldest drugs used by humans and have diverse effects ranging from pain relief to addiction. While the activities of opiates and opioid neuropeptides have been studied in mammals, relatively little is known about opioid signaling in simpler animals.

The mechanisms behind many biological processes have been investigated using a worm called C. elegans as a model system because it has a simple body plan and its genes can be altered easily. The feeding behavior of C. elegans is no exception. This worm feeds by contracting and relaxing its pharyngeal muscle to move food into its gut. When the worms sense that food is available, this ‘pharyngeal pumping’ is regulated by one type of nerve cell. Slow pharyngeal pumping also continues in starved worms when food is not available, possibly to encourage them to eat new potential sources of food. However, this slow pumping does not require the same type of nerve cell.

Cheong et al. hypothesized that the slow pumping in starved worms might depend on neuropeptide signaling instead, and have now tested this idea using engineered worms that made lower levels of a number of these molecules. The experiments uncovered a molecule called NLP-24 that promotes the slow pharyngeal pumping. This molecule is similar to opioid neuropeptides found in mammals. Worms that made less NLP-24 than normal grew more slowly; this suggests that they had problems feeding. Moreover, the levels of NLP-24 were found to increase in normal worms soon after they were deprived of food. Further experiments revealed the identity of the receptor for this molecule, which is also similar to mammalian opioid receptors.

The discovery that opioid signaling is involved in C. elegans' feeding behavior may well, in future, also help to identify new molecular players involved in opioid signaling. Further studies might also help the search for ways to reduce the problematic side-effects that limit the usefulness of opiate drugs as medicines.

DOI:http://dx.doi.org/10.7554/eLife.06683.002

Regulation of synaptic transmission at the Caenorhabditis elegans M4 neuromuscular junction by an antagonistic relationship between two calcium channels

In wild-type Caenorhabditis elegans, the synapse from motor neuron M4 to pharyngeal terminal bulb (TB) muscles is silent, and the muscles are instead excited by gap junction connections from adjacent muscles. An eat-5 innexin mutant lacking this electrical connection has few TB contractions and is unable to grow well on certain foods. We showed previously that this defect can be overcome by activation of the M4 → TB synapse. To identify genes that negatively regulate synaptic transmission, we isolated new suppressors of eat-5. To our surprise, these suppressors included null mutations in NPQR-type calcium channel subunit genes unc-2 and unc-36. Our results are consistent with the hypothesis that Ca(2+) entry through the NPQR-type channel inhibits synaptic transmission by activating the calcium-activated K(+) channel SLO-1, thus antagonizing the EGL-19 L-type calcium channel.

Falling asleep after a big meal: Neuronal regulation of satiety

C. elegans has become an ideal model to study genetics of appetite control and energy metabolism because of its robust conservation in molecular mechanisms underlying appetite control and in regulation of the relevant feeding behavior. Satiety behavior in worms in particular shows striking similarities to that in mammals, as a worm becomes quiescent after a big meal, mimicking post-prandial sleep in mammals. Here we review our recent finding regarding the neuronal regulation of the behavior and the implication of the finding such as cyclicity of behavioral states. Based on the finding, we propose a rather speculative but intriguing view of how metabolism could link to post-prandial sleep.

Methods for measuring pharyngeal behaviors

The pharynx is a neuromuscular pump at the anterior end of the alimentary tract. It is made up of 20 muscle cells, 20 neurons, and 20 other cells. Pharyngeal activity correlates with food intake. The proper feeding rate, as well as the precise timing of pharyngeal movements, is required for efficient feeding and likely for survival in nature. For most purposes, pharyngeal behavioral analysis requires no more than a routine stereomicroscope and a pair of eyes, but accuracy can be increased by video recording followed by off-line analysis in slow motion. Like other C. elegans behaviors, pharyngeal behavior is sensitive to both the immediate environmental conditions as well as to the history of such conditions.

Metabolic rate regulates L1 longevity in C. elegans

Animals have to cope with starvation. The molecular mechanisms by which animals survive long-term starvation, however, are not clearly understood. When they hatch without food, C. elegans arrests development at the first larval stage (L1) and survives more than two weeks. Here we show that the survival span of arrested L1s, which we call L1 longevity, is a starvation response regulated by metabolic rate during starvation. A high rate of metabolism shortens the L1 survival span, whereas a low rate of metabolism lengthens it. The longer worms are starved, the slower they grow once they are fed, suggesting that L1 arrest has metabolic costs. Furthermore, mutants of genes that regulate metabolism show altered L1 longevity. Among them, we found that AMP-dependent protein kinase (AMPK), as a key energy sensor, regulates L1 longevity by regulating this metabolic arrest. Our results suggest that L1 longevity is determined by metabolic rate and that AMPK as a master regulator of metabolism controls this arrest so that the animals survive long-term starvation.

Appetite Control: worm's-eye-view

Food is important to any animal, and a large part of the behavioral repertoire is concerned with ensuring adequate nutrition. Two main nutritional sensations, hunger and satiety, produce opposite behaviors. Hungry animals seek food, increase exploratory behavior and continue feeding once they encounter food. Satiated animals decrease exploratory behavior, take rest, and stop feeding. The signals of hunger or satiety and their effects on physiology and behavior will depend not only on the animal's current nutritional status but also on its experience and the environment in which the animal evolved. In our novel, nutritionally rich environment, improper control of appetite contributes to diseases from anorexia to the current epidemic of obesity. Despite extraordinary recent advances, genetic contribution to appetite control is still poorly understood partly due to lack of simple genetic model systems. In this review, we will discuss current understanding of molecular and cellular mechanisms by which animals regulate food intake depending on their nutritional status. Then, focusing on relatively less known muscarinic and cGMP signals, we will discuss how the molecular and behavioral aspects of hunger and satiety are conserved in a simple invertebrate model system, C. elegans so as for us to use it to understand the genetics of appetite control.

C. elegans feeding

C. elegans feeding depends on the action of the pharynx, a neuromuscular pump that joins the mouth to the intestine. The pharyngeal muscle captures food-bacteria-and transports it back to the intestine. It accomplishes this through a combination of two motions, pumping and isthmus peristalsis. Pumping, the most visible and best understood of the two, is a cycle of contraction and relaxation that sucks in liquid from the surrounding environment along with suspended particles, then expels the liquid, trapping the particles. Pharyngeal muscle is capable of pumping without nervous system input, but during normal rapid feeding its timing is controlled by two pharyngeal motor neuron types. Isthmus peristalsis, a posterior moving wave of contraction of the muscle of the posterior isthmus, depends on a third motor neuron type. Feeding motions are regulated by the presence and quality of food in the worm's environment. Some types of bacteria are better at supporting growth than others. Given a choice, worms are capable of identifying and seeking out higher-quality food. Food availability and quality also affect behavior in other ways. For instance, given all the high-quality food they can eat, worms eventually become satiated, stop eating and moving, and become quiescent.

Combretoxazolones: synthesis, cytotoxicity and antitumor activity

Two series of combretoxazolones including 3,4-diaryloxazolones (6) and 4,5-diaryloxazolones (7) were synthesized and evaluated for cytotoxicity and antitumor activity. Both series showed strong cytotoxicities against a variety of tumor cell lines. Compound 6g exhibited a significant antitumor activity in BDF1 mice bearing B16 murine melanoma cells with inhibition rates of 67 and 61% at 100 and 30 mg/kg/day, respectively.

Naphthazarin derivatives (VIII): Synthesis, inhibitory effect on DNA topoisomerase-I, and antiproliferative activity of 6-(1-acyloxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones

6-(1-Acyloxyalkyl)-5,8-dimethoxy-1,4-naphthoquinone (DMNQ; 5,8-dimethoxy-1,4-naphthoquinone) derivatives were synthesized and examined for their inhibitory effect on DNA topoisomerase-I (Topo I) and their antiproliferative activity against L1210 cells. The Topo-I inhibitory effect of 6-(1-hydroxyalkyl)-DMNQ derivatives was found to be dependent on the size of the alkyl chains, suggesting that lipophilicity might be one important factor influencing the inhibitory effect. It was found that acylation of 6-(1-hydroxyalkyl)-DMNQ derivatives possessing alkyl chains of C2-C5 enhanced both bioactivities, suggesting that an increase of electrophilicity in the quinoid moiety makes the electrophilic arylation of bionucleophiles more favorable. It is noteworthy that 6-(1-heptanoyloxyethyl)-DMNQ exhibited both the most potent Topo I inhibitory activity (IC50, 11.5 microM) and the greatest antiproliferative activity (ED50, 0.05 microM) upon L1210 cells.

Naphthazarin derivatives (VII): antitumor action against ICR mice bearing ascitic S-180 cells

Various analogues of 5,8-dimethoxy-1,4-naphthoquinone (DMNQ) such as 2- or 6-(1-hydroxyiminoalkyl)-DMNQs were prepared and evaluated for the antitumor action. (1-Hydroxyiminoalkyl)-DMNQ derivatives expressed greater antitumor action than (1-hydroxyalkyl)- or acyl-DMNQ derivatives. Moreover, 6-(1-hydroxyiminoalkyl)-DMNQ derivatives expressed higher antitumor action than 2-sudstituted ones, suggestive of a steric effect. Some of 6-(1-propyloxyalkyl)-DMNQ derivatives with an alkyl group of butyl to octyl moiety showed T/C values of >400%.

Syntheses of Certain 3-Aryl-2-propenoates and Evaluation of their Cytotoxicity

A series of 3-aryl-2-propenoates including cinnamates, (E)-methyl/ethyl 3-[2-(1,4-dimethoxy-5,8-dione)naphthalenyl]-2-propenoates (8ba, 8bb) and (E)-methyl/ethyl 3-[2-(1,4-dihydroxy-9,10-dione)anthracenyl]-2-propenoates (9aa,9ab) was synthesized and evaluated for antitumor cytotoxicity. It was found that the ortho- or para-dihydroxy funtionality on the aryl ring was essential for the cytotoxicity of cinnamates. Compounds 8ba, 8bb and 9aa, 9ab showed potent cytotoxicity against various tumor cell lines.

Esters of chlorambucil with 2-substituted 1,4-dihydroxy-9,10-anthraquinones as multifunctional anticancer agents

Novel twelve esters of chlorambucil with 2-(1-hydroxyalkyl)-1,4-dihydroxy-9,10-anthraquinone were synthesized and tested for their antitumor activity in mice bearing S-180 ascitic cells as well as cytotoxic activity against L1210 cells. Eight of them were highly cytotoxic on L1210 cells (ED(50), <6 microg mL(-1)) and derivatives 1 and 12 (T/C, 200 and 205%) appeared more active in vivo than chlorambucil (T/C, 168%).

Naphthazarin derivatives (VII): antitumor action against ICR mice bearing ascitic S-180 cells

Various analogues of 5,8-dimethoxy-1,4-naphthoquinone (DMNQ) such as 2- or 6-(1-hydroxyiminoalkyl)-DMNQs were prepared and evaluated for the antitumor action. (1-Hydroxyiminoalkyl)-DMNQ derivatives expressed greater antitumor action than (1-hydroxyalkyl)- or acyl-DMNQ derivatives. Moreover, 6-(1-hydroxyiminoalkyl)-DMNQ derivatives expressed higher antitumor action than 2-sudstituted ones, suggestive of a steric effect. Some of 6-(1-propyloxyalkyl)-DMNQ derivatives with an alkyl group of butyl to octyl moiety showed T/C values of >400%

(E) -6-(1-alkyloxyiminoalkyl)-5,8-dimethoxy-1,4-naphthoquinones: synthesis, cytotoxic activity and antitumor activity

All of 13 (E)-6-(1-alkyloxyiminomethyl)-5,8-dimethoxy-1,4-naphthoquinone derivatives synthesized showed high ED50 values, ranging from 0.1 to 0.3 microg/mL against L1210 cells. However, they were inactive on A549 cells. Nine compounds exhibited higher T/C (%) values (318-388%) than Adriamycin (T/C, 315%).

Naphthazarin derivatives (VI): synthesis, inhibitory effect on DNA topoisomerase-I and antiproliferative activity of 2- or 6-(1-oxyiminoalkyl)-5,8-dimethoxy-1,4-naphthoquinones

2- or 6-(1-Hydroxyiminoalkyl)-5,8-dimethoxy-1,4-naphthoquin-one (DMNQ) and 6-(1-propyloxyimino- alkyl)-DMNQ derivatives were synthesized, and their inhibitory effects on DNA topoisomerase-I (TOPO-I) and antiproliferative activities against L1210 cells were examined. In a comparison, it was found that 6-(1-hydroxyiminoalkyl)-DMNQ derivatives exhibited higher potencies in both bioactivities than 2-(1-hydroxyiminoalkyl)-DMNQ analogues, suggesting that the difference in bioactivities between two positional isomers might be due to the steric hindrance of the side chain. It is noteworthy that the optimal size of alkyl group for both bioactivities of 6-(1-hydroxyiminoalkyl)-DMNQ derivatives was pentyl to octyl (IC50, 22-29 microM) for the inhibition of TOPO-I and propyl to nonyl (ED50, 0.12-0.19 microM) for the antiproliferative activity. In addition, a similar potency of bioactivities was expressed by 6-(1-propyloxyiminoalkyl)-DMNQ derivatives, propylation products of the oximes.

Naphthazarin derivatives (IV): synthesis, inhibition of DNA topoisomerase I and cytotoxicity of 2- or 6-acyl-5,8-dimethoxy-1, 4-naphthoquinones

Some 2- or 6-acyl-5,8-dimethoxy-1,4-naphthoquinone (DMNQ) derivatives were synthesized and evaluated for inhibition of DNA topoisomerase I and cytotoxicity against L1210 cells. Compared with 2-acyl-DMNQ derivatives, 6-acyl-DMNQ compounds, bearing a higher electrophilic quinone moiety, showed a higher potency in the inhibition of DNA topoisomerase I and the cytotoxicity, implying the possible participation of electrophilic arylation in their bioactivities. Time and temperature dependence of the enzyme inhibition suggests that the arylation occurs irreversibly. Among the 6-acyl-DMNQ derivatives, the ones possessing an acyl group of an intermediate size (C(5)-C(9)) showed higher potency in their bioactivities than other derivatives. Furthermore, for the effective inhibition of DNA topoisomerase I, the size of acyl moiety of 6-acylated derivatives seems to be limited to < 12 carbon atoms.

Naphthazarin derivatives (II): formation of glutathione conjugate, inhibition of DNA topoisomerase-I and cytotoxicity

6-(1-Hydroxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones, expressing a higher reactivity in conjugation with glutathione, showed a greater potency in the inhibition of DNA topoisomerase-I and the cytotoxicity against L1210 cells than 2-(1-hydroxyalkyl)-DMNQ derivatives, implying the participation of electrophilic arylation in the bioactivities. In further study 6-(1-Hydroxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones with an alkyl group of shorter chain length (C2-C6) exerted a greater bioactivities than those with longer chain length(>C6).

Glutathione conjugates of 2- or 6-substituted 5,8-dimethoxy-1,4-naphthoquinone derivatives: formation and structure

Thirty-four glutathione conjugates of 5,8-dimethoxy-1,4-naphthoquinones (DMNQ) were synthesized and their structure was determined. The yield of GSH conjugate was dependent on size of alkyl group; the longer the size of alkyl group was, the lower was the yield. It was also found that the length of alkyl side chain influenced the chemical shift of quinonoid protons; the quinonoid protons of 2-glutathionyl DMNQ derivatives with R=H to propyl, 6.51-6.59 ppm vs. other ones with R=butyl to heptyl, 6.64-6.68 ppm. This was explained to be due to a folding effect of longer alkyl group. Glutathione (GSH) reacted with DMNQ derivative first to form a 1,4-adduct (2- or 3-glutathionyl-1,4-dihydroxy-5,8-dimethoxynaphthalenes) and then, the adduct was autooxidized to 2- or 3-glutathionyl-DMNQ derivatives. Moreover, GSH reduced DMNQ derivatives to their hydrogenated products. It was suggested that such an organic reaction might play an important role for a study of metabolism or toxicity of DMNQ derivatives in the living cells.

6-(1-alkenoyloxyalkyl)-5,8-dimethoxy-1,4-naphthoquinone derivatives:synthesis and evaluation of antitumor activity

Thirty six 5,8-dimethoxy-1,4-naphthoquinone derivatives, which bear unsaturated alkyl side chain with ester bond, were synthesized and tested cytotoxic activity on L1210 cells and antitumor activity against ICR mice bearing S-180 cells. It could be recognized that the cytotoxicities of naphthoquinones with R1 being methyl and propyl (IV1-24) were not enhanced by replacing the alkanoyls with alkenoyls. In contrast, the introduction of the alkenoyl moieties on the compounds with R1 = hexyl (IV25-36) resulted in the enhancement of their cytotoxicities. Replacement of alkanoyl group with an alkenoyl group generally increased the T/C value of the mice bearing S-180 cells.

Naphthazarin derivatives: synthesis, cytotoxic mechanism and evaluation of antitumor activity

The rate of the GSH conjugate formation, the inhibition of DNA topoisomerase-I and the cytotoxic activity against L1210 cells of the naphthoquinones showed the same order; 5,8-dimethoxy-1,4-naphthoquinone (DMNQ) > 6-(1-hydroxyethyl)-DMNQ > 2-(1-hydroxyethyl)-DMNQ; the steric hindrance of the substituents, particularly 2-substutuent, in reacting with cellular nucleophiles must be the main cause for lowering the bioactivities. Acetylation of 2-(1-hydroxyethyl)-DMNQ producing 2-(acetyloxyethyl)-DMNQ potentiated the bioactivities; 2-(1-hydroxyethyl)-DMNQ did not react with GSH and the enzyme, and showed ED50 of 0.680 microgram/ml, whereas the values of 2-(1-acetyloxyethyl)-DMNQ were the conjugate formation of 0.14 microM, IC50 value of 81 microM for the enzyme inhibition and ED50 of 0.146 microgram/ml for the cytotoxcity. Furthermore, the acetylation 2-(1-hydroxyethyl)-DMNQ (T/C, 119%) enhanced the T/C values for the mice bearing S-180 tumor [T/C of 2-(1-acetyloxyethyl)-DMNQ, 276%]. It was assumed that the difference in bioactivities ensued by acetylation was based on the mechanism of the so-called bioreductive alkylation.

The effects of hepatic cryosurgery on tumor growth in the liver

BACKGROUND

The effects of hepatic cryosurgery on residual hepatic tumor growth, and on tumor immunity, have not been determined.

MATERIALS AND METHODS

Two experiments were performed. In both, animals (n = 10 per group) had solitary left lobe hepatomas established, and underwent left lobectomy, cryoablation, or control laparotomy. Experiment I: immediately after tumor treatment, intraportal challenge of hepatoma cells was performed to evaluate for the effects of treatment on residual hepatic tumor growth. Experiment II: animals were challenged 14 days after tumor treatment, and splenocyte cytotoxicity assays were performed to evaluate for tumor immunity. Hepatic tumor nodules were counted 3 weeks after challenge in both experiments.

RESULTS

In animals challenged immediately after tumor treatment, the mean number of liver nodules at 3 weeks was similar between control and cryoablation groups (65 +/- 13 vs 115 +/- 38, P = 0.17). Animals that had undergone resection, however, had a significant increase in the mean number of nodules as compared to cryoablation (278 +/- 74 vs 115 +/- 38, P = 0. 04) and control (278 +/- 74 vs 65 +/- 13, P = 0.002) animals. In addition, only resection animals had elevation in serum levels of the growth factor FGF-basic, 48 h after treatment (mean = 30 +/- 14 pg/ml). In animals challenged 14 days following treatment, all groups had similar numbers of nodules (resection vs cryoablation, P = 0.8). Splenocyte cytotoxicity was not increased after cryosurgical treatment.

CONCLUSIONS

Unlike partial hepatectomy, cryoablation of hepatomas in rats does not accelerate residual tumor growth in the liver or result in production of the growth factor FGF-basic. We did not find evidence for the development of tumor immunity following cryosurgery.