Synthesis, phloem mobility and induced plant resistance of synthetic salicylic acid amino acid or glucose conjugates

BACKGROUND

The growing demand for food, combined with a strong social expectation for a diet produced with fewer conventional agrochemical inputs, has led to the development of new alternatives in plant protection worldwide. Among different possibilities, the stimulation of the plant innate immune system by chemicals represents a novel and promising way. The vectorization strategy of an active ingredient that we previously developed with fungicides can potentially extend to salicylic acid (SA) or its halogenated analogues.

RESULTS

Using the click chemistry method, six new conjugates combining SA or two mono- or di-halogenated analogues with L-glutamic acid or β-D-glucose via a 1,2,3-triazole nucleus have been synthesized. Conjugate 8a, which is derived from SA and glutamic acid, showed high phloem mobility in the Ricinus model, similar to that of SA alone despite a much higher steric hindrance. In vivo bioassays of the six conjugates against two maize pathogenic fungi Bipolaris maydis and Fusarium graminearum revealed that, unlike SA, the amino acid conjugate 8a with good phloem mobility exerted a protective effect not only locally at the application site, but also in distant stem tissues after foliar application. Moreover, compounds 8a and 8b induced up-regulation of both defense-related genes ZmNPR1 and ZmPR1 similar to their parent compounds upon challenge inoculation with B. maydis.

CONCLUSION

The vectorization of salicylic acid or its halogenated derivatives by coupling them with an α-amino acid can be a promising strategy to stimulate SA-mediated plant defenses responses against pathogens outside the application site. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Pharmacotherapeutic strategies for patients treated for depression in UK primary care: a database analysis

OBJECTIVE

To investigate long-term patterns of antidepressant treatment in patients in primary care in the UK, and to assess their healthcare resource use and disease outcomes.

RESEARCH DESIGN AND METHODS

A retrospective longitudinal cohort study was conducted using the Clinical Practice Research Datalink. The study population comprised patients aged ≥18 years with depression receiving a prescription for antidepressant monotherapy between 1 January 2006 and 31 December 2011 with no antidepressants within the preceding 6 months. Recovery was defined by timing of antidepressant prescriptions (≥6 months without treatment). Treatment lines and strategies (switching, combining, augmenting and resuming medication) were analyzed. Healthcare resource use for the different treatment strategies and periods of no therapy was assessed.

RESULTS

Data from 123,662 patients (287,564 treatment lines) were analyzed. Switching and resumption of treatment were more frequent than other strategies. Recovery was highest with first-line monotherapy (45% of patients), while as a second-line strategy switching was more successful (43%) than combination or augmentation. In subsequent lines of treatment, switching was associated with successively lower rates of recovery (31% in the third line and 24% from the fourth line onwards). Similar rates were observed for resumption. Healthcare resource use was greater during antidepressant use than treatment-free periods. Augmentation was associated with the highest proportions of patients with a psychiatrist referral, psychologist referral and psychiatric hospitalization.

CONCLUSIONS

This study provides extensive real-world information on the prescribing patterns and treatment outcomes for a large cohort of patients treated for depression with antidepressants in primary care. Switching is more frequently used than augmentation or combination treatment, with decreasing effectiveness across successive lines. Key limitations of the study were: (i) risk of selection bias due to the use of inclusion criteria based on depression diagnoses recorded by the practitioner; and (ii) reliance on prescribing patterns as proxies for clinical outcomes, such as recovery.

Antidepressant switching patterns in the treatment of major depressive disorder: a General Practice Research Database (GPRD) Study

AIMS

To investigate switching patterns of major antidepressant treatments and associated factors in a primary care adult population with major depressive disorder (MDD) using data from the General Practitioner Research Database (GPRD).

METHODS

A retrospective cohort study was conducted using the GPRD. The study included patients with MDD, aged [18-70], with a new prescription for amitriptyline, citalopram, escitalopram, fluoxetine, paroxetine, sertraline or venlafaxine between January 1, 2001 and September 30, 2003 and having no antidepressant prescription in the 6 months preceding index date. Switching of antidepressant treatment was defined as a prescription of a different antidepressant among all available marketed antidepressant treatment at this time (no restriction of compound) from 1 month before up to 2 months after the calculated end of the previous antidepressant treatment. Survival analysis techniques were used to describe switching of antidepressant and time to switch. Profiles of switchers were described and by-treatment analyses performed.

RESULTS

Data from over 59,000 patients showed that 16% switched antidepressants. Seventy-two per cent of switches appeared within 3 months after treatment initiation. Within switchers, median time to switch was 53 days. Switching patients had generally a more severe psychiatric profile, including more previous episodes of depression or other psychiatric disorders. They also had a higher proportion of concurrent psychiatric disorders (especially anxiety) and concomitant prescription of anxiolytics or hypnotics. Patients initially prescribed amitriptyline were almost twice as likely to switch (27%) as patients prescribed venlafaxine (17%) or an SSRI (15%).

CONCLUSIONS

This population-based study confirmed that antidepressant switch is more likely to occur within the first 3 months of treatment and in patients with a more severe psychiatric profile. A particular attention paid to these patients within the early phase of treatment may therefore help to improve their management.

Chlorophyll a might structure a community of potentially pathogenic culturable Vibrionaceae. Insights from a one-year study of water and mussels surveyed on the French Atlantic coast

The present study focused on the isolation of culturable bacteria from mussels and sea water to identify Vibrionaceae potentially pathogenic for humans. Three sites located on the French Atlantic coast were monitored monthly (twice each month during summer) for 1 year. Environmental parameters were surveyed (water temperature, salinity, turbidity, chlorophyll a) and bacteria were detected by culture and identified by API 20E(®) systems (BioMérieux) and PCR. A total of seven species were detected (Grimontia hollisae, Photobacterium damselae, Vibrio alginolyticus, V. cholerae, V. fluvialis, V. vulnificus and V. parahaemolyticus) and species diversity was higher at the end of summer. Surprisingly, V. cholerae non-O1/non-O139 was detected in spring. No site effect was detected. Using Sørensen similarity indices and statistical analyses, we showed that chlorophyll a had a significant influence on the bacterial community detected in mussels and assemblages were more similar to one another when chlorophyll a values were above 20 µg l(-1) . No significant effect of any parameter was found on the community detected in water samples. Such surveys are essential for the understanding of sanitary crises and detection of emerging pathogens.

Plasmodium berghei ANKA: selection of resistance to piperaquine and lumefantrine in a mouse model

We have selected piperaquine (PQ) and lumefantrine (LM) resistant Plasmodium berghei ANKA parasite lines in mice by drug pressure. Effective doses that reduce parasitaemia by 90% (ED(90)) of PQ and LM against the parent line were 3.52 and 3.93 mg/kg, respectively. After drug pressure (more than 27 passages), the selected parasite lines had PQ and LM resistance indexes (I(90)) [ED(90) of resistant line/ED(90) of parent line] of 68.86 and 63.55, respectively. After growing them in the absence of drug for 10 passages and cryo-preserving them at -80 degrees C for at least 2 months, the resistance phenotypes remained stable. Cross-resistance studies showed that the PQ-resistant line was highly resistant to LM, while the LM-resistant line remained sensitive to PQ. Thus, if the mechanism of resistance is similar in P. berghei and Plasmodium falciparum, the use of LM (as part of Coartem) should not select for PQ resistance.

Tegumental alterations in juvenile Schistosoma haematobium harboured in hamsters following artemether treatment

We report the findings of a detailed temporal study on tegumental alterations in juvenile Schistosoma haematobium, induced by artemether, using scanning electron microscopy. Hamsters infected with S. haematobium cercariae for 28 days were treated intragastrically with a single dose of 300 mg/kg artemether. Groups of two hamsters were killed 24 h, 72 h and 7 days after treatment, and schistosomula were recovered from livers by perfusion and subsequent systematic examination of the tissue, before routinely processing for scanning electron microscopic examination. Most schistosomula collected 24 h after artemether administration showed severe tegumental damage, usually including swelling, fusion, vesiculation, peeling and collapse of enlarged sensory structures. After 72 h, tegumental damage had increased and schistosomula generally showed contraction with extensive swelling, erosion and peeling of the tegument. Seven days post-treatment, severe tegumental damage was only seen in a single male specimen with swelling of the worm body and destruction of the oral sucker. The other schistosomula showed only light to moderate damage, suggesting that schistosomula surviving the treatment began to recover. Our findings of tegumental damage following artemether treatment correlate with the efficacy of this novel antischistosomal drug in killing the juvenile stages of S. haematobium and complement recent findings with S. japonicum and S. mansoni.

Effect of combined treatment with praziquantel and artemether on Schistosoma japonicum and Schistosoma mansoni in experimentally infected animals

Praziquantel and artemether are safe and efficacious antischistosomal drugs that act against different developmental stages of the parasite: praziquantel against adult worms and artemether against schistosomula. A combined treatment has been suggested as a strategy for transmission control. Recent laboratory experiments with rabbits with a mixed infection of Schistosoma japonicum parasites of different ages confirmed the effectiveness of a combination therapy. In the present work, we assessed the effect of a combined treatment on adult worms of S. japonicum and found significantly higher worm reduction rates than with a single dose of praziquantel. In a next step, we extended the study of the combined treatment to Schistosoma mansoni. A combined treatment with 75 mg/kg praziquantel and 150 mg/kg artemether was administered to hamsters infected with juvenile and adult S. mansoni. The two drugs, administered simultaneously or spaced by 6 h, 1, 3 or 7 days, resulted in significantly higher worm reduction rates than a single treatment with praziquantel. A combination therapy with increased doses of 100 mg/kg praziquantel and 300 mg/kg artemether showed very high worm reduction rates of 90% and above, however, some hamsters died in five different combined treatment experiments, suggesting that these drug concentrations were too high. We conclude that a combined treatment with praziquantel and artemether at the lower doses is safe and more effective than praziquantel alone, which forms a foundation for designing respective clinical trials in humans.

Histopathological changes in juvenile Schistosoma haematobium harboured in hamsters treated with artemether

Histopathological changes in juvenile Schistosoma haematobium, caused by artemether administered to the infected hamsters, were studied. Hamsters were infected with S. haematobium cercariae, and after 28 days, a single dose of artemether (300 mg/kg) was administered intragastrically. After 24 h, 72 h and 7 days, groups of two hamsters were sacrificed, and livers were removed, fixed and processed routinely, and examined by light microscopy. After 24 h, 93% of the schistosomulae examined showed degeneration, which included swelling of the tegument, adherence of inflammatory cells to the damaged tegument, collapsed and damaged intestine, and infiltration of inflammatory cells, predominantly lymphocytes. After 72 h, the intensity of damage increased, including severe swelling of the tegument, loss of definition in the internal structures, collapse of intestine accompanied by release of pigment particles to the parenchymal tissues, and emergence of dead schistosomulae. Seven days after treatment, the number of dead schistosomulae increased, and most of them developed to an early- or late stage of dead worm granuloma. Meanwhile, 12% of the schistosomulae showed a normal appearance, which suggested that those schistosomulae that had survived the treatment were recovered to normal. The results demonstrated that artemether effectively acts against the juvenile stages of S. haematobium and confirms earlier results with S. japonicum and S. mansoni.

Artemether administered together with haemin damages schistosomes in vitro

We conducted experiments in vitro to assess the effect of artemether in combination with haemin on adult Schistosoma japonicum, S. mansoni and S. haematobium. When schistosomes were maintained in a medium containing artemether at concentrations of 20 micrograms/mL or less for 72 h, no apparent effect on the schistosomes was seen. When the medium contained 50 or 100 micrograms/mL haemin as well as artemether, the schistosomes showed decreased motor activity 2-24 h after exposure, which was followed by the staining of the whole worm body a reddish-yellow colour, dilatation of the intestine, and extensive vesiculation of the tegument. Some of the schistosomes died 24 h after exposure, and almost all died within 48-72 h. When schistosomes were exposed to the same concentrations of haemin alone, they were stained a light yellow colour but there was no apparent effect on their survival. Our findings suggest that artemether interacts with haemin to exert a toxic effect on the worms, which might be of importance in the further elucidation of the mechanism of action of artemether on schistosomes.

Tegumental changes in adult Schistosoma mansoni harbored in mice treated with artemether

A detailed temporal examination was made of alterations induced by artemether in the tegument of adult Schistosoma mansoni worms using scanning electron microscopy (SEM). Mice infected with S. mansoni cercariae 42 days previously were treated intragastrically with artemether at a single dose of 400 mg/kg. Groups of 3 mice were killed at 24 hr, 72 hr, and 7 days after treatment; the worms were collected by perfusion and examined by SEM. Twenty-four hours after artemether treatment, focal damage to the tubercles on the tegumental surface of male worms was seen. In both male and female worms, there was focal swelling and fusion of tegumental ridges, and sometimes peeling. After 72 hr, the damage to the tegument had increased, especially in female worms, with extensive swelling, fusion, and peeling of the tegumental ridges. In the most severely damaged worms, host leukocytes were seen to be adhered to the damaged tegument. Damage to the oral sucker was also occasionally seen in both male and female worms. Seven days after treatment, the appearance of the tegument had returned to normal in some male and female worms, whereas others still showed apparent damage. The results demonstrate that artemether damages the tegument of adult S. mansoni, and the intensity of damage is more severe in female worms than in males.

Tegumental changes in adult Schistosoma mansoni harboured in mice treated with praziquantel enantiomers

Praziquantel administered to the host causes damage to the tegument of Schistosoma mansoni. In this study, the effects of racemic praziquantel (Pra) and its enantiomers, levo-praziquantel (L-Pra) and dextro-praziquantel (D-Pra) were compared using scanning electron microscopy (SEM). Mice infected with S. mansoni for 49 days were treated with a single dose of Pra (300 mg/kg), L-Pra (150 mg/kg) or D-Pra (150 or 600 mg/kg). Groups of three mice were killed after 4 and 24 h, and schistosomes collected by perfusion and examined by SEM. Treatment with Pra or L-Pra, for 4 or 24 h, caused tegumental damage to S. mansoni including severe swelling, vacuolization, fusion of the tegumental ridges and loss or shortening of the spines on the tubercles, collapse and peeling. After treatment with D-Pra at 150 mg/kg, no apparent damage was observed. When the dosage was increased to 600 mg/kg, after 4 h lesions on the tegument similar to those induced by Pra or L-Pra were seen, but less severe. After 24 h, there was evidence of recovery. The study thus clearly showed that L-Pra was more active than D-Pra in causing tegumental damage. D-Pra showed a qualitatively similar activity at a higher concentration. It is possible that this effect was due at least to some extent to the small amount of L-Pra (<2%) which was present in the preparation of D-Pra used.

Effect of artemether against Schistosoma haematobium in experimentally infected hamsters

The drug, artemether, has been shown to be active against the juvenile stages of Schistosoma japonicum and Schistosoma mansoni in experimentally infected animals, while it is less effective on adult worms. These findings have been confirmed in randomised controlled trials in humans. Consequently, it could be expected that artemether is also active against Schistosoma haematobium. We present here the first results from experiments assessing the effect of artemether on S. haematobium. Hamsters with a single infection received intra-gastrically an initial dose of 300 mg/kg artemether on day 14, 21 or 28, followed by further doses at varying treatment regimens. In all the treatment groups, the total and female worm reduction rates were highly significant, and ranged from 78 to 100% in hamsters harbouring juvenile schistosomes. Hamsters infected three times with S. haematobium, on days 0, 4 and 9, and repeatedly treated with artemether at the same dose as above, showed highly significant total and female worm reduction rates of between 94 and 99%. Artemether was also active against 77-day-old adult S. haematobium, since its administration on two consecutive days resulted in highly significant total and female worm reduction rates of 76-89%. Our findings confirm that artemether is also active against S. haematobium, especially the schistosomules. These results provide a basis for clinical trials in humans, for further assessment of the potential of artemether for schistosomiasis control.

Tegumental changes in 21-day-old Schistosoma mansoni harboured in mice treated with artemether

Alterations in the tegument of 21-day-old Schistosoma mansoni, caused by artemether administered to the infected mice, were studied using scanning electron microscopy (SEM). Mice were infected with S. mansoni cercariae, and after 21 days a single dose of artemether (400 mg/kg) was administered intragastrically. After 24, 72 h and 7 days groups of three mice were killed and the schistosomules collected by perfusion, fixed and processed routinely, and examined by SEM. After 24 h, all male and female worms examined showed alterations in the tegument, characterised by swelling, vesiculation and fusion of tegumental ridges; peeling, erosion and collapse of damaged tegumental surface, and also destruction of the oral sucker and acetabulum. After 72 h, severe damage to the tegument was seen, usually including extensive peeling, swelling and vesiculation, and host leukocytes were adhered to the damaged surface. Some worms were surrounded by clusters of host leukocytes or had even disintegrated. Seven days after treatment, some schistosomules still showed severe tegumental damage, but in some cases the damage was less than at earlier times, which suggested that those schistosomules that had survived were beginning to recover. The ability of artemether to cause severe damage to the tegument correlates with its high efficacy in killing 21-day-old schistosomules.

Preventive effect of artemether in experimental animals infected with Schistosoma mansoni

The effect of artemether, an antimalarial drug developed from the plant Artemisia annua, has been tested against the larval stages of Schistosoma mansoni covering the time from skin penetration to the early adult liver-stage. The results show that the experimental animals used (hamster and mice) do not develop schistosomiasis mansoni if treated with artemether during the first month after infection. The parasite was found to be especially susceptible between the 3rd and 4th week after infection, resulting in worm reductions of 75.3-82.0% compared to non-treated controls. This level was boosted to 97.2-100% when the animals were subjected to various schedules of repeated treatment. Almost complete protection was also reached in parallel experiments with repeated infections carried out to mirror more closely the real situation of trickle infection.

Phenyl beta-methoxyacrylates: a new antimalarial pharmacophore

Phenyl beta-methoxyacrylates, linked to an aromatic ring via an olefinic bridge, have been identified as novel, potentially inexpensive, antimalarial agents. The compounds are believed to exert their activity by inhibition of mitochondrial electron transport at the cytochrome bc(1) complex. A series of compounds have been synthesized to define structure-activity relationships affecting antimalarial activity. It was found that the beta-methoxyacrylate was required ortho to the linker and the optimal bridge was (E,E)-butadiene. Compounds in which the second aromatic ring was ortho-substituted or ortho,para-disubstituted gave optimal potency. Several compounds were identified with potency that is superior to that of chloroquine both in culture and in a murine malaria model.

Synthesis and antimalarial activity of 11 dispiro-1,2,4,5-tetraoxane analogues of WR 148999. 7,8,15,16-Tetraoxadispiro[5.2.5.2]hexadecanes substituted at the 1 and 10 positions with unsaturated and polar functional groups

Eleven novel dispiro-1,2,4,5-tetraoxanes 3 bearing unsaturated and polar functional groups were designed to enhance the oral antimalarial activity of the prototype tetraoxane 2 (WR 148999). With the exception of 3g and 3h, tetraoxanes 3 were available via the peroxidation of corresponding cyclohexanone derivatives in H2SO4/CH3CN. Tetraoxanes 3g and 3h were prepared by hydrolysis of ester tetraoxanes 3e and 3i, respectively. Five of the 11 tetraoxanes were inactive, but six tetraoxanes had IC50 values of 6-26 nM against the K1 and NF54 strains of Plasmodium falciparum compared to corresponding IC50 values of 28 and 39 nM for 2, and 10 and 12 nM for artemisinin (1). Ester tetraoxane 3e was the most active in vitro, some 2-fold more potent than 1. However, none of the six tetraoxanes active in vitro were as effective as either 1 or 2 in vivo; at single doses of 100 mg/kg most possessed little to no vivo activity in mice infected with Plasmodium berghei. Unsaturated tetraoxane 3a was uniquely more active when administered per os (po) than subcutan (sc). For this series of tetraoxanes, the discrepancy between vitro and vivo activities underscores the limitations of conclusions drawn solely from in vitro antimalarial data and illustrates a practical benefit of complementary single-dose in vivo antimalarial screens.

Antimalarial activity of the bicyclic peroxide Ro 42-1611 (arteflene) in experimental models

The sesquiterpene peroxide Ro 42-1611 (arteflene), a synthetic derivative of yingzhaosu, was evaluated extensively against various drug-sensitive and drug-resistant lines of Plasmodium falciparum in vitro and P. berghei in vivo in mice. The potential therapeutic and prophylactic activities were studied comparatively with the standard antimalarials chloroquine, mefloquine and quinine, as well as qinghaosu and the derivatives artemether and artesunic acid. Experimentally arteflene proved to be a highly effective antimalarial drug. In vivo it is active at low doses against blood stages of P. berghei in mice after oral or parenteral administration. It has a rapid onset of drug action and a long lasting suppressive effect when given after infection, as well as a good potential for prophylactic activity when given before infection. The suppressive and prophylactic properties are comparable to chloroquine and superior to qinghaosu, artemether and artesunic acid. In vitro the compound showed no signs of cross-resistance with existing antimalarials. It was consistently rather more active against drug-resistant than against drug-sensitive strains of P. falciparum. Drug interaction studies in vitro and in vivo with chloroquine, mefloquine and quinine revealed an additive to synergistic effect with arteflene. Antagonism with these drugs was not observed. Compared with standard antimalarials the activity of arteflene in vitro is lower than would be expected from the in vivo results. This may be due to pharmacokinetic properties of the compound and the formation of an active metabolite which sustains the activity of arteflene in vivo.