Saleh H. Alwasel

Capsaicin: A Potent Inhibitor of Carbonic Anhydrase Isoenzymes

Carbonic anhydrase (CA, EC 4.2.1.1) is a zinc containing metalloenzyme that catalyzes the rapid and reversible conversion of carbon dioxide (CO2) and water (H2O) into a proton (H+) and bicarbonate (HCO3–) ion. On the other hand, capsaicin is the main component in hot chili peppers and is used extensively used in spices, food additives and drugs; it is responsible for their spicy flavor and pungent taste. There are sixteen known CA isoforms in humans. Human CA isoenzymes I, and II (hCA I and hCA II) are ubiquitous cytosolic isoforms. In this study, the inhibition properties of capsaicin against the slow cytosolic isoform hCA I, and the ubiquitous and dominant rapid cytosolic isozymes hCA II were studied. Both CA isozymes were inhibited by capsaicin in the micromolar range. This naturally bioactive compound has a Ki of 696.15 µM against hCA I, and of 208.37 µM against hCA II.

Rosmarinic acid inhibits some metabolic enzymes including glutathione S-transferase, lactoperoxidase, acetylcholinesterase, butyrylcholinesterase and carbonic anhydrase isoenzymes

Abstract Rosmarinic acid (RA) is a natural polyphenol contained in many aromatic plants with promising biological activities. Carbonic anhydrases (CAs, EC 4.2.1.1) are widespread and intensively studied metalloenzymes present in higher vertebrates. Acetylcholinesterase (AChE, E.C. 3.1.1.7) is intimately associated with the normal neurotransmission by catalysing the hydrolysis of acetylcholine to acetate and choline and acts in combination with butyrylcholinesterase (BChE) to remove acetylcholine from the synaptic cleft. Lactoperoxidase (LPO) is an enzyme involved in fighting pathogenic microorganisms, whereas glutathione S-transferases (GSTs) are dimeric proteins present both in prokaryotic and in eukaryotic organisms and involved in cellular detoxification mechanisms. In the present study, the inhibition effects of rosmarinic acid on tumour-associated carbonic anhydrase IX and XII isoenzymes, AChE, BChE, LPO and GST enzymes were evaluated. Rosmarinic acid inhibited these enzymes with Kis in the range between micromolar to picomolar. The best inhibitory effect of rosmarinic acid was observed against both AChE and BChE.

The impact of hydroquinone on acetylcholine esterase and certain human carbonic anhydrase isoenzymes (hCA I, II, IX, and XII)

Abstract Carbonic anhydrases (CAs) are widespread and the most studied members of a great family of metalloenzymes in higher vertebrates including humans. CAs were investigated for their inhibition of all of the catalytically active mammalian isozymes of the Zn2+-containing CA, (CA, EC 4.2.1.1). On the other hand, acetylcholinesterase (AChE. EC 3.1.1.7), a serine protease, is responsible for ACh hydrolysis and plays a fundamental role in impulse transmission by terminating the action of the neurotransmitter ACh at the cholinergic synapses and neuromuscular junction. In the present study, the inhibition effect of the hydroquinone (benzene-1,4-diol) on AChE activity was evaluated and effectively inhibited AChE with Ki of 1.22 nM. Also, hydroquinone strongly inhibited some human cytosolic CA isoenzymes (hCA I and II) and tumour-associated transmembrane isoforms (hCA IX, and XII), with Kis in the range between micromolar (415.81 μM) and nanomolar (706.79 nM). The best inhibition was observed in cytosolic CA II.

The human carbonic anhydrase isoenzymes I and II (hCA I and II) inhibition effects of trimethoxyindane derivatives

Abstract Carbonic anhydrases (CAs, EC 4.2.1.1) had six genetically distinct families described to date in various organisms. There are 16 known CA isoforms in humans. Human CA isoenzymes I and II (hCA I and hCA II) are ubiquitous cytosolic isoforms. Acetylcholine esterase (AChE. EC 3.1.1.7) is a hydrolase that hydrolyzes the neurotransmitter acetylcholine relaying the signal from the nerve. In this study, some trimethoxyindane derivatives were investigated as inhibitors against the cytosolic hCA I and II isoenzymes, and AChE enzyme. Both hCA isozymes were inhibited by trimethoxyindane derivatives in the low nanomolar range. These compounds were good hCA I inhibitors (Kis in the range of 1.66–4.14 nM) and hCA II inhibitors (Kis of 1.37–3.12 nM) and perfect AChE inhibitors (Kis in the range of 1.87–7.53 nM) compared to acetazolamide as CA inhibitor (Ki: 6.76 nM for hCA I and Ki: 5.85 nM for hCA II) and Tacrine as AChE inhibitor (Ki: 7.64 nM).

Acetylcholinesterase and carbonic anhydrase isoenzymes I and II inhibition profiles of taxifolin

Abstract Taxifolin, also known as dihydroquercetin, is a flavonoid commonly found in plants. Carbonic anhydrase (CA, EC 4.2.1.1) plays an important role in many critical physiological events including carbon dioxide (CO2)/bicarbonate () respiration and pH regulation. There are 16 known CA isoforms in humans, of which human hCA isoenzymes I and II (hCA I and II) are ubiquitous cytosolic isoforms. In this study, the inhibition properties of taxifolin against the slow cytosolic isoenzyme hCA I, and the ubiquitous and dominant rapid cytosolic isoenzyme hCA II were studied. Taxifolin, as a naturally bioactive flavonoid, has a Ki of 29.2 nM against hCA I, and 24.2 nM against hCA II. For acetylcholinesterase enzyme (AChE) inhibition, Ki parameter of taxifolin was determined to be 16.7 nM. These results clearly show that taxifolin inhibited both CA isoenzymes and AChE at the nM levels.

Evaluation of cytotoxic, oxidative stress, proinflammatory and genotoxic effect of silver nanoparticles in human lung epithelial cells.

Silver nanoparticles are increasingly used in various products, due to their antibacterial properties. Despite its wide spread use, only little information on possible adverse health effects exists. Therefore, the aim of this study was to assess the toxic potential of silver nanoparticles (<100 nm) in human lung epithelial (A549) cells and the underlying mechanism of its cellular toxicity. Silver nanoparticles induced dose and time‐dependent cytotoxicity in A549 cells demonstrated by MTT and LDH assays. Silver nanoparticles were also found to induce oxidative stress in dose and time‐dependent manner indicated by depletion of GSH and induction of ROS, LPO, SOD, and catalase. Further, the activities of caspases and the level of proinflammatory cytokines, namely interleukin‐1β (IL‐1β) and interleukin‐6 (IL‐6) were significantly higher in treated cells. DNA damage, as measured by single cell gel electrophoresis, was also dose and time‐dependent signicants in A549 cells. This study investigating the effects of silver nanoparticles in human lung epithelial cells has provided valuable insights into the mechanism of potential toxicity induced by silver nanoparticles and warrants more careful assessment of silver nanoparticles before their industrial applications.

Antioxidant, antiradical, and anticholinergic properties of cynarin purified from the Illyrian thistle (Onopordum illyricum L.)

Abstract Cynarin is a derivative of hydroxycinnamic acid and it has biologically active functional groups constituent of some plants and food. We elucidated the antioxidant activity of cynarin by using different in vitro condition bioanalytical antioxidant assays like DMPD•+, ABTS•+, , DPPH• and H2O2 scavenging effects, the total antioxidant influence, reducing capabilities, Fe2+ chelating and anticholinergic activities. Cynarin demonstrated 87.72% inhibition of linoleic acid lipid peroxidation at 30 µg/mL concentration. Conversely, some standard antioxidants like trolox, α-tocopherol, butylated hydroxytoluene (BHT), and butylated hydroxyanisole (BHA) exhibited inhibitions of 90.32, 75.26, 97.61, 87.30%, and opponent peroxidation of linoleic acid emulsion at the identical concentration, seriatim. Also, cynarin exhibited effective DMPD•+, ABTS•+, , DPPH•, and H2O2 scavenging effects, reducing capabilities and Fe2+ chelating effects. On the contrary, IC50 and Ki parameters of cynarin for acetylcholinesterase enzyme inhibition were determined as 243.67 nM (r2: 0.9444) and 39.34 ± 13.88 nM, respectively. This study clearly showed that cynarin had marked antioxidant, anticholinergic, reducing ability, radical-scavenging, and metal-binding activities.

The effects of some bromophenols on human carbonic anhydrase isoenzymes.

Abstract Carbonic anhydrases (CAs, EC 4.2.1.1), which are involved in a variety of physiological and pathological processes, are ubiquitous metalloenzymes mainly catalyzing the reversible hydration of carbon dioxide (CO2) to bicarbonate () and proton (H+). In this study, a dozen of bromophenol derivatives (1–12) were evaluated as metalloenzyme CA (EC 4.2.1.1) inhibitors against the human carbonic anhydrase isoenzymes I and II (hCA I and II). Cytosolic hCA I and II isoenzymes were effectively inhibited by bromophenol derivatives (1–12) with Kis in the low nanomolar range of 1.85 ± 0.58 to 5.04 ± 1.46 nM against hCA I and in the range of 2.01 ± 0.52 to 2.94 ± 1.31 nM against hCA II, respectively.

Synthesis of some tetrahydropyrimidine-5-carboxylates, determination of their metal chelating effects and inhibition profiles against acetylcholinesterase, butyrylcholinesterase and carbonic anhydrase

Abstract 2-(Methacryloyloxy)ethyl 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate, is a cyclic urea derivative synthesized from urea, 2-(methacryloyloxy) ethyl acetoacetate and substituted benzaldehyde, and tested in terms of the inhibition of two physiologically relevant carbonic anhydrase (CA) isozymes I and II. Acetylcholinesterase (AChE) is found in high concentrations in the red blood cells and brain. Butyrylcholinesterase (BChE) is another enzyme abundantly present in the liver and released into blood in a soluble form. Also, they were tested for the inhibition of AChE and BChE enzymes and demonstrated effective inhibition profiles with Ki values in the range of 429.24–530.80 nM against hCA I, 391.86–530.80 nM against hCA II, 68.48–97.19 nM against AChE and 104.70–214.15 nM against BChE. On the other hand, acetazolamide clinically used as CA inhibitor, showed Ki value of 281.33 nM against hCA I, and 202.70 nM against hCA II. Also, Tacrine inhibited AChE and BChE showed Ki values of 396.03 and 209.21 nM, respectively.

Prenatal programming of renal sodium handling in the rat

Prenatally programmed hypertension induced by maternal protein restriction is associated with increased expression of the renal tubular Na+/K+/2Cl- co-transporter (NKCC2) and the Na+/Cl- co-transporter (NCC). This has led to the suggestion that renal Na+ retention contributes to the development of hypertension in the LP rat (offspring exposed to a maternal low-protein diet in utero). However, this hypothesis has not been tested in vivo. Renal clearance measurements in hypertensive 4-week-old male and female LP rats showed that, although the glomerular filtration rate remained unaltered, urine flow (P<0.01) and urinary Na+ excretion rates (1.6+/-0.3 and 3.0+/-0.4 mumol.min-1.100 g-1 of body weight in control male and LP male respectively; P<0.001) were increased. Na+ excretion was positively correlated with mean arterial pressure in both males (P<0.01) and females (P<0.05), but neither the slope nor the intercept differed between control and LP rats. Fractional excretion of Na+ was increased in male (1.5+/-0.2 and 3.0+/-0.5% in control and LP rats respectively; P<0.001) and female LP rats, implying reduced tubular reabsorption of Na+. Western blotting and quantitative PCR showed that NKCC2 expression was increased, whereas NCC mRNA was not up-regulated. Na+/K+ ATPase alpha1 subunit expression did not differ from controls; however, there was a significant reduction in whole kidney pump activity (23.4+/-1.8 and 17.7+/-1.2 nmol of phosphate.mug-1 of protein.h-1 in control male and male LP rats respectively; P<0.001); immunohistochemistry showed that the alpha1 subunit was virtually absent from the inner medulla. The greater Na+ excretion of LP rats can be explained, in part, by a pressure-natriuresis mechanism; however, the loss of the Na+/K+ ATPase alpha1 subunit from the inner medulla and up-regulation of NKCC2 suggests that altered renal Na+ handling is also programmed prenatally.