Cell death features induced in Leishmania major by 1,3,4-thiadiazole derivatives.

Under a variety of stress conditions, Leishmania species display some morphological and biochemical features characteristic of mammalian programmed cell death or necrosis. Nitroheteroaryl-1,3,4-thiadiazoles induce cell death in Leishmania major (L. major). Putative mechanisms of action of these compounds were investigated in vitro at cellular and molecular levels. We used colorimetric assay to measure acid phosphatase activity which is an indicator of cell viability in the promastigotes. The mode of toxicity was determined by detection of phosphatidylserine translocation to the surface, evaluation of cell membrane integrity, and in situ dUTP nick end-labeling assay. We also determined poly-ADP-ribose polymerase-like protein (PARP) level in the parasites after treatment. A significant reduction of acid phosphatase level, one of the most crucial and virulent factors of the parasite was found in parasites treated with 1,3,4-thiadiazole derivatives. In addition, 1,3,4-thiadiazole derivatives induced loss of plasma membrane integrity, DNA breakage, proteolysis of PARP and necrotic-like death in the parasites.

Schwann cell apoptosis and p75(NTR) siRNA.

The p75 pan-neurotrophin receptor (p75(NTR)) plays a pivotal role in linking the immune system with the nervous system. p75(NTR) is required for the development of several characteristic features of allergic asthma. Also p75(NTR) upregulated by reactive Schwann cells after peripheral nerve injury. Moreover p75(NTR) and RhoA play a critical role in the regulation of apoptosis. To determine whether the designed siRNA for p75(NTR) can downregulates both p75(NTR) and Rho-A at RNA level in rats and, if so, at what magnitude, Schwann cell apoptosis occurs. Isolation and purification of neonate Schwann cells were prepared from rat sciatic nerve. Specific siRNA duplex was designed for p75(NTR) . To investigate the role of siRNA-mediated knockdown of p75(NTR) , the gene expression in p75(NTR) was examined with reverse transcription-polymerase chain reaction (RT-PCR) and Real-Time RT-PCR. Schwann cell apoptosis was performed by Annexin and TUNEL assays after 24 hours. Following p75(NTR) Transfection siRNA, p75(NTR) gene, compared with control, was downregulated by 73%. Without using siRNA for Rho-A, Rho-A gene was downregulated by 89% at the same time. Based on Annexin assay, apoptosis of Schwann cells occurred in siRNA+NGF and control+NGF by 16.76%±2.27 and 92.39%±1.82, respectively. TUNEL data showed that apoptosis of Schwann cells occurred in siRNA and control by 12.91%±6.39 and 78.55%±11.85, respectively. Thus, p75-siRNA downregulated both p75(NTR) and Rho-A at RNA level in rats and showed a role on decreased cell apoptosis compared to the controls.

Synthesis and antileishmanial activity of 5-(5-nitroaryl)-2-substituted-thio-1,3,4-thiadiazoles.

A series of novel 2-substituted-thio-1,3,4-thiadiazoles bearing a 5-nitroaryl moiety including nitrofuran, nitrothiophene or nitroimidazole at the 5-position and a bulky residue attached to the 2-position of the thiadiazole ring were synthesised as potential antileishmanial agents. The target compounds were evaluated against the promastigote form of Leishmania major using the tetrazolium bromide salt (MTT) colorimetric assay. All test compounds exhibited high activity against L. major promastigotes with 50% inhibitory concentrations (IC(50)) ranging from 1.11 to 3.16 µM. The structure-activity relationship study indicated that the S-pendant group attached to the 2-position of the thiadiazole ring has a high flexibility for structural alteration therefore retaining good antileishmanial activity.

Chromene-based synthetic chalcones as potent antileishmanial agents: synthesis and biological activity.

Two types of regioisomeric chromene-based chalcones namely, 1-(6-methoxy-2H-chromen-3-yl)-3-phenylpropen-1-ones and 3-(6-methoxy-2H-chromen-3-yl)-1-phenylpropen-1-ones were prepared and investigated for their antileishmanial activity against promastigotes form of Leishmania major. The obtained results from in vitro biological assays indicated that chloro-substituted 1-(6-methoxy-2H-chromen-3-yl)-3-phenylpropen-1-ones exhibited excellent activity against Leishmania major at non-cytotoxic concentrations.

Novel antileishmanial chalconoids: synthesis and biological activity of 1- or 3-(6-chloro-2H-chromen-3-yl)propen-1-ones.

A series of novel chalconoids containing a 6-chloro-2H-chromen-3-yl group were prepared through a convenient and efficient synthetic method by using 5-chloro-2-hydroxybenzaldehyde as starting material. The target compounds were evaluated against the promastigote form of Leishmania major using MTT assay. All of the evaluated compounds have shown high in vitro antileishmanial activity at concentrations less than 3.0 microM. The results of cytotoxicity assessment against mouse peritoneal macrophage cells showed that these compounds display antileishmanial activity at non-cytotoxic concentrations.

Selective leishmanicidal effect of 1,3,4-thiadiazole derivatives and possible mechanism of action against Leishmania species.

With the aim of determining selectivity and the possible target(s) of nitroheteroaryl-1,3,4-thiadiazoles considered as possible leads for the development of anti-leishmanial agents, we studied 5-nitroimidazole, 5-nitrofuran and 5-nitrothiophene analogs of N-substituted-piperazinyl-1,3,4-thiadiazoles. We investigated 21 representative compounds 1-3(a-g) for the following properties: selectivity and efficiency against different Leishmania wild type species and intracellular parasite, toxicity against host cells and inhibition of topoisomerases I and II. Our results indicate that the nitroimidazole analogs 1a and 1f, and nitrofuran derivatives 2a, 2b, 2c, 2f, and 2g exhibited low toxicity against the host cells (IC(50)> or =80 microM), but high selectivity against intracellular amastigotes (selectivity index>12). Leishmania topoisomerases revealed impressive sensitivity to the agents (%inhibition >50 at IC(50) doses of compounds against Leishmania). Our findings showed that at least part of leishmaniacidal effect of the compounds could be attributed to disruption DNA-relaxed activities of topoisomerases I and II, and cleavable-complex formation.

Nitroimidazolyl-1,3,4-thiadiazole-based anti-leishmanial agents: synthesis and in vitro biological evaluation.

A series of 1-[5-(1-methyl-5-nitro-1H-imidazol-2-yl)-1,3,4-thiadiazol-2-yl]-4-aroylpiperazines were synthesized and evaluated in vitro against Leishmania major. Most of the target compounds exhibited good anti-leishmanial activity against the promastigote form of L. major at non-cytotoxic concentrations. The most active compound was 1-[(5-chloro-2-thienyl)carbonyl]-4-[5-(1-methyl-5-nitro-1H-imidazol-2-yl)-1,3,4-thiadiazol-2-yl]piperazine (5f) with an IC(50) value of 9.35+/-0.67 microM against L. major promastigotes. In addition, this compound was effective against intracellular L. major and significantly decreased the infectivity index.

Leishmanicidal evaluation of novel synthetic chromenes.

In the present paper, twelve chromenes were synthesized by coupling of 2,2,8,8-tetramethyl-8H-pyrano[2,3-f]chroman-4-one 1 with various aryl and benzylmagnesium chlorides. The synthetic compounds were examined for in-vitro activity against Leishmania major, and some of them displayed efficient anti-leishmanial activity. Among the compounds tested, compounds 9 (4-(2-chloro-benzylidene)-2,2,8,8-tetramethyl-3,4-dihydro-2H,8H-pyrano[2,3-f]chromene 9a and 4-(2-chloro-benzyl)-2,2,8,8-tetramethyl-2H,8H-pyrano[2,3-f]chromene 9b) were the most active with an inhibitory activity of 73.4%.

Synthesis and in vitro anti-leishmanial activity of 1-[5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-yl]- and 1-[5-(5-nitrothiophen-2-yl)-1,3,4-thiadiazol-2-yl]-4-aroylpiperazines.

The synthesis and anti-leishmanial activity of nitroheteroaryl-1,3,4-thiadiazole-based compounds including 1-[5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-yl]-4-aroylpiperazines and 1-[5-(5-nitrothiophen-2-yl)-1,3,4-thiadiazol-2-yl]-4-aroylpiperazines were described. Most of the synthesized compounds exhibited potent anti-leishmanial activity against both promastigote and amastigote forms of Leishmania major at non-cytotoxic concentrations. In general, 5-nitrofuran derivatives were more active than the corresponding 5-nitrothiophene analogues.