No abstract

Rheumatoid arthritis (RA) is a chronic inflammatory disease, leading to progressive destruction of joints and extra-articular tissues, including organs such as liver and spleen. The purpose of this study was to compare the effects of a potential immunomodulator, natural polyphenol N-feruloylserotonin (N-f-5HT), with methotrexate (MTX), the standard in RA therapy, in the chronic phase of adjuvant-induced arthritis (AA) in male Lewis rats. The experiment included healthy controls (CO), arthritic animals (AA), AA given N-f-5HT (AA-N-f-5HT), and AA given MTX (AA-MTX). N-f-5HT did not affect the body weight change and clinical parameters until the 14th experimental day. Its positive effect was rising during the 28-day experiment, indicating a delayed onset of N-f-5HT action. Administration of either N-f-5HT or MTX caused reduction of inflammation measured as the level of CRP in plasma and the activity of LOX in the liver. mRNA transcription of TNF-α and iNOS in the liver was significantly attenuated in both MTX and N-f-5HT treated groups of arthritic rats. Interestingly, in contrast to MTX, N-f-5HT significantly lowered the level of IL-1β in plasma and IL-1β mRNA expression in the liver and spleen of arthritic rats. This speaks for future investigations of N-f-5HT as an agent in the treatment of RA in combination therapy with MTX.

The purpose of this work was to study the catalytic properties of rat butyrylcholinesterase with benzoylcholine (BzCh) and N‐alkyl derivatives of BzCh (BCHn) as substrates. Complex hysteretic behaviour was observed in the approach to steady‐state kinetics for each ester. Hysteresis consisted of a long lag phase with damped oscillation. The presence of a long lag phase, with no oscillations, in substrate hydrolysis by rat butyrylcholinesterase was also observed with N‐methylindoxyl acetate as substrate. Hysteretic behaviour was explained by the existence of two interconvertible butyrylcholinesterase forms in slow equilibrium, while just one of them is catalytically active. The damped oscillations were explained by the existence of different substrate conformational states and/or aggregates (micelles) in slow equilibrium. Different substrate conformational states were confirmed by 1H‐NMR. The Km values for substrates decreased as the length of the alkyl chain increased. High affinity of the enzyme for the longest alkyl chain length substrates was explained by multiple hydrophobic interactions of the alkyl chain with amino acid residues lining the active site gorge. Molecular modelling studies supported this interpretation; docking energy decreased as the length of the alkyl chain increased. The long‐chain substrates had reduced kcat values. Docking studies showed that long‐chain substrates were not optimally oriented in the active site for catalysis, thus explaining the slow rate of hydrolysis. The hydrolytic rate of BCH12 and longer alkyl chain esters vs. substrate concentration showed a premature plateau far below Vmax. This was due to the loss of substrate availability. The best substrates for rat butyrylcholinesterase were short alkyl homologues, BzCh – BCH4.

Microsomal esterases were used in the study of the in vitro enzymic hydrolysis of the ester bond in alkyl(2-benzoyloxyethyl)dimethylammonium bromides. These compounds are potential "soft" disinfectants, easily biodegradable to nontoxic biologically inactive hydrolytic products, namely substituted choline and benzoic acid. Formation of the latter product was used to monitor the kinetics of the reaction. It has been found that the rate of enzymic hydrolysis is substantially influenced by different length of the alkyl chain on the ammonium nitrogen. At the same time, interspecies (rat-mouse) and interorgan (liver-kidney) variability has been observed.

The physiological function of butyrylcholinesterase (EC 3.1.1.8, BChE) is not clearly understood, but a role was suggested in the fat utilization process, resulting in positive correlation between plasma triglyceride (TG) levels and BChE activity. Consequently we tested the hypothesis that regular intake of betaine, a natural compound intervening in the liver TG metabolism could influence the BChE activity. The BChE activity was estimated spectrophotometrically in plasma of rats fed with betaine enriched standard (B) or high-fat diet (HFB). The results confirmed decreased TG plasma levels after betaine treatment independently on the type of diet (0.15±0.03 (B) vs. 0.27±0.08 (control) mmol/l; p=0.003 and 0.13±0.03 (HFB) vs. 0.27±0.08 (control) mmol/l; p=0.005). The BChE activity increased significantly with betaine administration, however the change was more distinct in the HFB group (0.84±0.34 (HFB) vs. 0.22±0.04 (control) O.D./min/mg; p<0.001 and 0.41±0.11 (B) vs. 0.22±0.04 (control) O.D./min/mg; p=0.001). In conclusion, betaine intake led to elevated BChE activity in plasma and this effect was potentiated by the HF diet. Since betaine is in general used as a supplement in the treatment of liver diseases accompanied by TG overload, its impact on the BChE activity in the role of the liver function marker should be taken into account.