Coumarins as factor XIIa inhibitors: Potency and selectivity improvements using a fragment-based strategy

Previously, we described weak coumarin inhibitors of factor XIIa, a promising target for artificial surface-induced thrombosis and various inflammatory diseases. In this work, we used fragment-based drug discovery approach to improve our coumarin series. First, we screened about 200 fragments for the S1 pocket. The S1 pocket of trypsin-like serine proteases, such as factor XIIa, is highly conserved and is known to drive a major part of the association energy. From the screening, we selected fragments displaying a micromolar activity and studied their selectivity on other serine proteases. Then, these fragments were merged to our coumarin templates, leading to the generation of nanomolar inhibitors. The mechanism of inhibition was further studied by mass spectrometry demonstrating the covalent binding through the formation of an acyl enzyme complex. The most potent compound was tested in plasma to evaluate its stability and efficacy on coagulation assays. It exhibited a plasmatic half-life of 1.9 h and a good selectivity for the intrinsic coagulation pathway over the extrinsic one.

Capillary electrophoresis as a fragment screening tool to cross-validate hits from chromogenic assay: Application to FXIIa

In this study, a partial-filling affinity capillary electrophoresis (pf-ACE) method was developed for the cross-validation of fragment hits revealed by chromogenic factor XIIa (FXIIa) assay. Chromogenic assay produces false positives, mainly due to spectrophotometric interferences and sample purity issues. pf-ACE was selected as counter-screening technology because of its separative character and the fact that the target does not have to be attached or tagged. The effects of protein plug length, applied voltage and composition of the running buffer were examined and optimized. Detection limit in terms of dissociation constant was estimated at 400 μM. The affinity evaluation was performed close to physiological conditions (pH 7.4, ionic strength 0.13 mol L^-1) in a poly (ethylene oxide)-coated capillary of 75 μm internal diameter x 33 cm length with an applied voltage of 3 kV. This method uncovered chromogenic assay's false positives due to zinc contamination. Moreover, pf-ACE supported the evaluation of compounds absorbing at 405 nm.

Association between plasminogen activator inhibitor‑1 (PAI-1) 4G/5G polymorphism and circulating PAI-1 level in systemic lupus erythematosus and rheumatoid arthritis : A meta-analysis

OBJECTIVE

This study systemically reviewed the evidence regarding the association between plasminogen activator inhibitor‑1 (PAI‑1) 4G/5G polymorphism and susceptibility to systemic lupus erythematous (SLE)/lupus nephritis (LN) and rheumatoid arthritis (RA) and the relationship between circulating PAI‑1 levels and SLE/LN and RA.

METHODS

We conducted a meta-analysis on the association between the PAI‑1 4G/5G polymorphism and SLE/LN or RA risk and serum/plasma PAI‑1 levels in patients with SLE/LN and RA and healthy controls.

RESULTS

Nine articles including 657 patients with SLE and 668 controls and 567 patients with RA and 772 controls were included. No association was revealed between SLE and PAI‑1 4G allele in all study subjects (odds ratio [OR] = 0.944, 95% confidence interval [CI] = 0.808-1.102, p = 0.463). Ethnicity-based stratification showed no association between the PAI‑1 4G allele and SLE among Europeans and Asians. No association was detected between LN and RA and the PAI‑1 4G allele (OR = 0.886, 95% CI = 0.713-1.102, p = 0.278; OR = 0.8736, 95% CI = 0.747-1.020, p = 0.088, respectively) or between SLE/LN and RA and the PAI‑1 4G/5G polymorphism using the recessive and dominant models and homozygote contrast. The circulating PAI‑1 level was significantly higher in the SLE group than in the control group (standardized mean difference [SMD] = 0.337, 95% CI = 0.057-0.619, p = 0.019). However, serum/plasma PAI‑1 level showed no significant difference between RA and control group (SMD = 0.333, 95% CI = -0.6989-1.35, p = 0.527).

CONCLUSIONS

There was no association between the PAI‑1 4G/5G polymorphism and SLE/LN and RA development and significantly higher levels of circulating PAI‑1 were observed in patients with SLE but not in those with RA.

Beneficial implications of sugar beet proteinase inhibitor BvSTI on plant architecture and salt stress tolerance in Lotus corniculatus L

Food demands of increasing human population dictate intensification of livestock production, however, environmental stresses could jeopardize producers' efforts. Forage legumes suffer from yield losses and poor nutritional status due to salinity increase of agricultural soils. As tools aimed to reduce negative impacts of biotic or abiotic stresses, proteinase inhibitors (PIs) have been promoted for biotechnological improvements. In order to increase tolerance of Lotus corniculatus L. to salt stress, serine PI, BvSTI, was introduced into this legume using Agrobacterium rhizogenes, with final transformation efficiency of 4.57%. PCR, DNA gel-blot, RT-PCR and in-gel protein activity assays confirmed the presence and activity of BvSTI products in transformed lines. Plants from three selected transgenic lines (21, 73 and 109) showed significant alterations in overall phenotypic appearance, corresponding to differences in BvSTI accumulation. Lines 73 and 109 showed up to 7.3-fold higher number of tillers and massive, up to 5.8-fold heavier roots than in nontransformed controls (NTC). Line 21 was phenotypically similar to NTC, accumulated less BvSTI transcripts and did not exhibit an additional band of recombinant trypsin inhibitor as seen in lines 73 and 109. Exposure of the transgenic lines to NaCl revealed different levels of salt stress susceptibility. The NaCl sensitivity index, based on morphological appearance and chlorophyll concentrations showed that lines 73 and 109 were significantly less affected by salinity than NTC or line 21. High level of BvSTI altered morphology and delayed salt stress related senescence, implicating BvSTI gene as a promising tool for salinity tolerance improvement trials in L. corniculatus.

Anti-lymphoproliferative activity of alpha-2-macroglobulin in the plasma of hibernating 13-lined ground squirrels and woodchucks

Plasma from hibernating (HIB) woodchucks (Marmota monax) or 13-lined ground squirrels (Ictidomys tridecemlineatus) suppressed (3)H-thymidine uptake in mouse spleen cell cultures stimulated with Concanavalin A (ConA); plasma from non-hibernating animals were only slightly inhibitory. Maximum inhibition occurred when HIB plasma was added to the cultures prior to ConA. After HPLC size exclusion chromatography of the HIB ground squirrel plasma, a single fraction (fraction-14) demonstrated inhibitory activity. Assay of fraction-14 from 8 HIB squirrels showed inhibition ranging from 13 to 95%; inhibition was correlated to the time the squirrels were exposed to cold prior to hibernation. Western blot analysis showed the factor to be a large molecular weight protein (>300 kDa), and mass spectrometry identified sequences that were 100% homologous with alpha-2-macroglobulin from humans and other species. These findings indicate a hibernation-related protein that may be responsible for immune system down regulation.