Nanoencapsulated deltamethrin as synergistic agent potentiates insecticide effect of indoxacarb through an unusual neuronal calcium-dependent mechanism.

The use of neurotoxic chemical insecticides has led to consequences against the environment, insect resistances and side-effects on non-target organisms. In this context, we developed a novel strategy to optimize insecticide efficacy while reducing doses. It is based on nanoencapsulation of a pyrethroid insecticide, deltamethrin, used as synergistic agent, combined with a non-encapsulated oxadiazine (indoxacarb). In this case, the synergistic agent is used to increase insecticide efficacy by activation of calcium-dependant intracellular signaling pathways involved in the regulation of the membrane target of insecticides. In contrast to permethrin (pyrethroid type I), we report that deltamethrin (pyrethroid type II) produces an increase in intracellular calcium concentration in insect neurons through the reverse Na/Ca exchanger. The resulting intracellular calcium rise rendered voltage-gated sodium channels more sensitive to lower concentration of the indoxacarb metabolite DCJW. Based on these findings, in vivo studies were performed on the cockroach Periplaneta americana and mortality rates were measured at 24 h, 48 h and 72 h after treatments. Comparative studies of the toxicity between indoxacarb alone and indoxacarb combined with deltamethrin or nanoencapsulated deltamethrin (LNC-deltamethrin), indicated that LNC-deltamethrin potentiated the effect of indoxacarb. We also demonstrated that nanoencapsulation protected deltamethrin from esterase-induced enzymatic degradation and led to optimize indoxacarb efficacy while reducing doses. Moreover, our results clearly showed the benefit of using LNC-deltamethrin rather than piperonyl butoxide and deltamethrin in combination commonly used in formulation. This innovative strategy offers promise for increasing insecticide efficacy while reducing both doses and side effects on non-target organisms.

µ-Theraphotoxin-An1a: primary structure determination and assessment of the pharmacological activity of a promiscuous anti-insect toxin from the venom of the tarantula Acanthoscurria natalensis (Mygalomorphae, Theraphosidae).

Tarantulas are included in the mygalomorph spider family Theraphosidae. Although the pharmacological diversity of theraphosid toxins (theraphotoxins) is broad, studies dedicated to the characterization of biologically active molecules from the theraphosid genus Acanthoscurria have been restricted to the investigation of antimicrobial peptides and polyamines produced by the hemocytes of Acanthoscurria gomesiana. The present study reports the purification, primary structure determination and electrophysiological effects of an anti-insect toxin, named µ-theraphotoxin-An1a (µ-TRTX-An1a), from the venom of Acanthoscurria natalensis - a tarantula species occurring in the Brazilian biomes caatinga and cerrado. The analysis of the primary structure of µ-TRTX-An1a revealed the similarity of this toxin to theraphosid toxins bearing a huwentoxin-II-like fold. Electrophysiological experiments showed that µ-TRTX-An1a (100 nM) induces membrane depolarization, increases the spontaneous firing frequency and reduces spike amplitude of cockroach dorsal unpaired median (DUM) neurons. In addition, under voltage-clamp conditions, µ-TRTX-An1a (100 nM) only partially blocks voltage-dependent sodium current amplitudes in DUM neurons without any effect on their voltage dependence. This effect correlates well with the reduction of the spontaneous action potential amplitudes. Altogether, these last results suggest that µ-TRTX-An1a affects insect neuronal voltage-dependent sodium channels, which are among possible channels targeted by this promiscuous toxin.

Characterization of tyramine ß-hydroxylase, an enzyme upregulated by stress in Periplaneta americana.

Octopamine (OA) is an important neuroactive substance that modulates several physiological functions and behaviors of various invertebrate species. This biogenic monoamine, structurally related to noradrenaline, acts as a neurotransmitter, a neuromodulator, or a neurohormone in insects. The tyramine ß-hydroxylase (TBH) catalyzes the last step in OA biosynthesis and thus plays a key role in the regulation of synthesis and secretion of OA in neurons. The aim of this study was to characterize TBH in the cockroach Periplaneta americana and to get a better understanding of its regulation under stress conditions in this insect. First of all, five full-length cDNAs encoding TBH isoforms were cloned from the nerve cord of the physiological model P. americana. PaTBH transcripts were found mainly expressed in nervous tissues and in octopaminergic dorsal unpaired median neurons. In addition, a new ELISA assay was developed so as to allow determination of both OA level and TBH activity in stressed cockroaches. Mechanical stressful stimulation led to a significant increase in TBH activity after 1 and 24  h, with a higher induction after 1  h than after 24  h. Thus, TBH could be considered as a promising biomarker of stress in insects rather than OA.

Synthesis and antitumoral activity of novel thiazolobenzotriazole, thiazoloindolo[3,2-c]quinoline and quinolinoquinoline derivatives.

The biological evaluation of some novel thiazoloindolo[3,2-c]quinoline, 8-substituted-11H-indolo[3,2-c]quinolines is described. These compounds were obtained via Graebe-Ullmann thermal cyclization from appropriated N-arylated benzotriazoles. 7H-4,7-Diaza-benzo[de]anthracene, a reaction by-product structurally closed to the pyridoacridine skeleton was also identified. All thiazolobenzotriazole intermediates were tested in vitro for their capacity to inhibit the growth of two breast cancer cell lines, MCF-7 and MDA-MB-231. In parallel, the newly synthesized skeletons were evaluated for DNA interaction, topoisomerases' inhibition, and cytotoxicity against HL60 and HL60/MX2 human leukemia cells. Most compounds showed a potent growth inhibitory effect on all the tested cell lines, with IC(50) in the muM range.

Synthesis and evaluation of the antiproliferative activity of novel thiazoloquinazolinone kinases inhibitors.

The microwave-assisted synthesis of a family of 2,8-substituted thiazoloquinazolinones is described. The preliminary evaluation of the antiproliferative activity and the capacity of these molecules to inhibit CDKs and GSK-3 are reported. A lead compound was identified, constituting a scaffold from which more potent inhibitors could be designed.