Activation of GPR55 alleviates neuropathic pain and chronic inflammation.

Neuropathic pain (NP) significantly impacts the quality of life due to its prolonged duration and lack of effective treatment. Recent findings suggest that targeting neuroinflammation is a promising approach for treating NP. G protein-coupled receptor 55 (GPR55), a member of the GPCR family, plays an important role in neuroinflammatory regulation. CID16020046, a GPR55 agonist, possesses promising anti-neuroinflammatory effects. Herein, the therapeutic effect of CID16020046 on NP was investigated in an NP rat model. The NP model was established using the unilateral sciatic nerve chronic constriction injury (CCI) assay. Both sham and CCI rats were intraperitoneally administered with 20 mg/kg CID16020046. NP was assessed using paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). First, we showed that GPR55 was downregulated in the spinal dorsal horn of CCI rats. After CCI rats were treated with CID16020046, the values of PWT and PWL were increased, indicating their effect on pain relief. The treated rats had attenuated release of inflammatory cytokines in the spinal cord, decreased spinal malondialdehyde (MDA) levels, and increased spinal glutathione peroxidase (GSH-PX) activity. Additionally, the increased levels of phosphorylated nuclear factor (NF)-κB p65 in CCI rats were significantly alleviated by CID16020046 treatment. Mechanistically, we showed that CID16020046 significantly suppressed the activation of the Janus kinase (JAK2)/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway in the spinal cord of CCI-treated rats. However, Colivelin TFA (a STAT3 agonist) abolished the effect of CID16020046 on JAK2/STAT3 activation. In conclusion, our data demonstrate that the activation of GPR55 by CID16020046 alleviates NP and neuroinflammation in CCI rats by mediating the JAK2/STAT3 pathway.

Non-covalent complexes between bis-beta-carbolines and double-stranded DNA: A study by electrospray ionization FT-ICR mass spectrometry (I).

The non-covalent complexes of five bis-beta-carbolines alkaloids with three different double-stranded oligodeoxynucleotides d(GCGCGATCGCGC)(2), d(GCGCAATTGCGC)(2), and d(GCGAAATTTCGC)(2) were investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. These five antitumor compounds all showed DNA-binding abilities. Binding affinities in the order of 2>3, 4>5, and 1 with double-stranded DNA were obtained, which mean that the length of the linkage chain between two beta-carbolines has a remarkable effect on the formation of the non-covalent complexes. Additionally, the preliminary results indicated that bis-beta-carbolines had no notable sequence selectivities.

Effect of temperature on the acidolysis of N-acyl-N,alpha,alpha-trialkyl glycine amides as related to the nature of substituents.

The C-terminal amide bond of N-acyl-N,alpha,alpha-trialkyl glycine amides is labile to acid and this has been currently assigned to steric crowding within the amino acid residue. However, our previous work has shown that in the acidolysis of some of these compounds steric hindrance seems to play a less important role than what one would expect. Thus, the cleavage of two sets of such compounds bearing different degrees of crowding was investigated at five different temperatures in order to clarify the effect of structure on reactivity in terms of enthalpy and entropy of activation. The compounds exhibited an Arrhenius-type behaviour, and both enthalpies and entropies of activation were calculated by taking advantage of the transition state theory. In addition, the kinetic data were analysed in terms of isokinetic relationships in order to find evidence to support that the compounds react under the same mechanism. The changes in the reaction rate are governed by the changes in both the enthalpy and the entropy of activation, which are related to bond energy and steric hindrance, respectively. In general, the entropies of activation are very negative for all compounds investigated, which reflects large steric constrictions associated with the formation of the transition state. In addition, they are very sensitive to the structure of the substrates.

Kinetic and mechanistic investigation of the selective acidolysis of the C-terminal amide bond of N-acyl-N,alpha,alpha-trialkyl glycine amides.

Accurate rate constants were calculated from HPLC kinetic measurements of the selective acidolysis of the C-terminal amide bond of eight N-acyl-N-(4-methoxybenzyl)-alpha,alpha-trialkyl glycine amides in TFA at 25.00 degrees C. The results were in all cases consistent with a first order behaviour with respect to the substrate and, apparently, also to the acid, and a clear relationship between reactivity and structure could be observed. The data collected also allowed experimental evidence to be obtained for the first time in support of the previously postulated formation of an intermediate oxazolonium salt. In the case of the more crowded species this intermediate compound undergoes slow hydrolytic ring opening, which takes place in competition with cleavage of the N-alkyl group to give another oxazolonium derivative that hydrolysed still more slowly. The stability of the intermediate cyclic compounds may result either from conjugation of the phenyl group with the oxazolonium ring in the case of N-benzoyl derivatives, or from conformational assistance imparted by the bulky amino acid side chains of the alpha,alpha-dialkyl glycine species, or both. The loss of the N-alkyl group also seems to be assisted by the bulkiness of the amino acid side chains, which thus tends to decrease the selectivity of cleavage.

Kinetic investigation of the effect of the amino acid side chains in the selective acidolysis of N-acyl-N,alpha,alpha-trialkyl glycine amides.

Accurate kinetic measurements of the rate constants for the acidolysis of five N-acetyl-N-(4-methoxybenzyl)-alpha,alpha-trialkyl glycine cyclohexyl amides in TFA were performed at 25 degrees C and the reactions monitored by HPLC. In all cases the results were consistent with a first order behaviour with respect to the substrate. No direct correlation was obtained with these data between the rate constant values and structure, but a good correlation coefficient was obtained when a multiple regression analysis was applied by taking advantage of a Taft equation using appropriate polar and steric substituent parameters. In a plot of the values observed for log k against those calculated by this equation all five points fell very close to the line of perfect correlation. The calculated sensitivity coefficients to polar and steric contributions were used to discuss the experimental results and showed that the acidolysis were comparatively less affected by steric effects than expected.

Synthesis of N-acyl-N,alpha,alpha-trialkyl and N-acyl-alpha,alpha-dialkyl glycines by selective cleavage of Ugi-Passerini adducts. Qualitative assessment of the effect of substituents on the path and yield of reaction.

Several symmetric N-acyl-N,alpha,alpha-trialkyl glycine amides were synthesised by the Ugi-Passerini four-component reaction and subjected to selective cleavage with trifluoroacetic acid. In almost all cases it was possible to obtain the corresponding N-acyl-N,alpha,alpha-trialkyl and N-acyl-alpha,alpha-dialkyl glycines in fair to good yields directly from the reaction adducts. With some of the bulkier compounds our results show that the selectivity of cleavage is concentration dependent with respect to the acid, which suggests kinetically controlled processes. The isolation of a stable oxazolone as the product of some of the reactions seems to confirm that amide cleavage involves in all cases formation of an oxazolone-type derivative.

Cytotoxic bis-3,4-dihydro-beta-carbolines and bis-beta-carbolines.

Ten bis-beta-carboline 1, 2 and bis-3,4-dihydro-beta-carboline 3, 4 derivatives, linked between carbons 1 and 1' by a polymethylene spacer, were synthesized from bistryptamine amides 9, 10. Some of them display a micromolar IC50 towards L-1210 cells.