Effects of the Usage of l-Cysteine (l-Cys) on Human Health

Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

Potentiometric redox sensing is a relatively inexpensive and passive approach to evaluate the overall redox state of complex biological and environmental solutions. The ability to make such measurements in ultra-small volumes using high surface area, nanoporous electrodes is of particular importance as such electrodes can improve the rates of electron transfer and reduce the effects of biofouling on the electrochemical signal. This work focuses on the fabrication of miniaturized nanoporous gold (NPG) electrodes with a high surface area and a small footprint for the potentiometric redox sensing of three biologically relevant redox molecules (ascorbic acid, uric acid, and cysteine) in microliter volumes. The NPG electrodes were inexpensively made by attaching a nanoporous gold leaf prepared by dealloying 12K gold in nitric acid to a modified glass capillary (1.5 mm id) and establishing an electrode connection with copper tape. The surface area of the electrodes was ~1.5 cm², providing a roughness factor of ~16 relative to the geometric area of 0.09 cm². Scanning electron microscopy confirmed the nanoporous framework. A linear dependence between the open-circuit potential (OCP) and the logarithm of concentration (e.g., Nernstian-like behavior) was obtained for all three redox molecules in 100 μL buffered solutions. As a first step towards understanding a real system, the response associated with changing the concentration of one redox species in the presence of the other two was examined. These results show that at NPG, the redox potential of a solution containing biologically relevant concentrations of ascorbic acid, uric acid, and cysteine is strongly influenced by ascorbic acid. Such information is important for the measurement of redox potentials in complex biological solutions.

Oral l-Cysteine Supplementation Enhances the Long Term-Effect of Topical Basic Fibroblast Growth Factor (bFGF) in Reducing the Corneal Haze after Photorefractive Keratectomy in Myopic Patients

We aimed at evaluating the long-term effects of l-cysteine oral supplementation to basic fibroblast growth factor (bFGF) eye-drops on corneal re-epithelization and transparency in myopic patients subjected to photorefractive keratectomy (PRK). Forty patients subjected to bilateral PRK for myopia were enrolled and randomly divided into two groups receiving an additional therapy together with the standard postoperative treatment consisting in local tobramycin 0.3%, dexamethasone 0.1%, diclofenac 0.1%, and 0.2% hyaluronate. Group 1 included 20 patients (11 males and 9 females; 34.09 ± 8 years of age) receiving only bFGF eye-drops (10 μg/10 μL) four times a day for 7 days starting from the day of surgery; Group 2 included 20 patients (12 males and 8 females; 37.35 ± 11.5 years of age) who were postoperatively administered with topical basic fibroblast growth factor (bFGF; 10 μg/10 μL) four times a day for 7 days plus oral l-cysteine supplementation (500 mg/capsule) once a day for 15 days, starting 7 days before PRK. Patients were followed-up for 12 months. Clinical ophthalmologic parameters were recorded for all the 80 examined eyes. The corneal transparency was evaluated in vivo by slit lamp and confocal microscopy. The data showed that: (a) the corneal haze occurred in a smaller percentage of the patients who were postoperatively administered with topical bFGF plus oral l-cysteine supplementation (Group 2) compared to patients who received only bFGF (Group 1); (b) at 6 months of follow-up, the stromal mean image brightness of the patients belonging to Group 2 was significantly lower than that of the Group 1 (p < 0.03), and, interestingly, the difference was even more evident at 12 month from the treatment (p < 0.001). Moreover, the final mean of the spherical equivalent refraction was −0.06 ± 0.2 D in Group 1 and −0.08 ± 0.3 D in Group 2, whereas the final uncorrected distance visual acuity (UDVA) was equal or superior to 20/25 in 100% of eyes in both Group 1 and 2. Post refractive patients can benefit from the administration of l-cysteine before the surgery and in association with bFGF in the early postoperative period, showing a faster corneal re-epithelization able to prevent corneal haze in the long-term recovery.

Neuroprotective mechanism of L-cysteine after subarachnoid hemorrhage

Hydrogen sulfide, which can be generated in the central nervous system from the sulfhydryl-containing amino acid, L-cysteine, by cystathionine-β-synthase, may exert protective effects in experimental subarachnoid hemorrhage; however, the mechanism underlying this effect is unknown. This study explored the mechanism using a subarachnoid hemorrhage rat model induced by an endovascular perforation technique. Rats were treated with an intraperitoneal injection of 100 mM L-cysteine (30 μL) 30 minutes after subarachnoid hemorrhage. At 48 hours after subarachnoid hemorrhage, hematoxylin-eosin staining was used to detect changes in prefrontal cortex cells. L-cysteine significantly reduced cell edema. Neurological function was assessed using a modified Garcia score. Brain water content was measured by the wet-dry method. L-cysteine significantly reduced neurological deficits and cerebral edema after subarachnoid hemorrhage. Immunofluorescence was used to detect the number of activated microglia. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the levels of interleukin 1β and CD86 mRNA in the prefrontal cortex. L-cysteine inhibited microglial activation in the prefrontal cortex and reduced the mRNA levels of interleukin 1β and CD86. RT-PCR and western blot analysis of the complement system showed that L-cysteine reduced expression of the complement factors, C1q, C3α and its receptor C3aR1, and the deposition of C1q in the prefrontal cortex. Dihydroethidium staining was applied to detect changes in reactive oxygen species, and immunohistochemistry was used to detect the number of NRF2- and HO-1-positive cells. L-cysteine reduced the level of reactive oxygen species in the prefrontal cortex and the number of NRF2- and HO-1-positive cells. Western blot assays and immunohistochemistry were used to detect the protein levels of CHOP and GRP78 in the prefrontal cortex and the number of CHOP- and GRP78-positive cells. L-cysteine reduced CHOP and GRP78 levels and the number of CHOP- and GRP78-positive cells. The cystathionine-β-synthase inhibitor, aminooxyacetic acid, significantly reversed the above neuroprotective effects of L-cysteine. Taken together, L-cysteine can play a neuroprotective role by regulating neuroinflammation, complement deposition, oxidative stress and endoplasmic reticulum stress. The study was approved by the Animals Ethics Committee of Shandong University, China on February 22, 2016 (approval No. LL-201602022).

Optimized one-pot derivatization and enantioseparation of cysteine: Application to the study of a dietary supplement

Cysteine is a sulfur-containing amino acid which plays an outstanding role in many biological pathways in mammals. The analysis and quantification of native cysteine remains a critical issue due to its highly reactive thiol group evolving to the disulfide cystine derivative through oxidation reaction. Aimed at improving the derivative stability, cysteine was labelled with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), which reacts with both amino and thiol groups. The derivatization was optimized and the chemical identity of the reaction product was assessed via high-resolution mass spectrometry. The NBD-cysteine derivative resulted stable for 10 days. This derivative was enantioresolved (α and R_S equal to 1.25 and 2.70, respectively) thanks to a (R,R)-Whelk-O1 phase with the following chromatographic setting: eluent, MeOH/water-90/10 (v/v) with 15 mM ammonium formate (pwsH 6.0); column temperature, 35 °C; flow rate, 1.0 mL/min. The developed method was validated following the ICH guidelines and applied for the quality control of a L-cysteine containing dietary supplement.

Dual chemosensor for the rapid detection of mercury(ii) pollution and biothiols

A new benzothiazole azo dye [(E)-1-((6-methoxybenzo[d]thiazole-2-yl)diazenyl)naphthalene-2,6-diol] (also known as “BAN”), has been synthesised and used as a chemosensor for the rapid and selective detection of mercury(ii) ions in water.

Design of a Zn-MOF biosensor via a ligand “lock” for the recognition and distinction of S-containing amino acids

A new method of introducing a ‘lock’ ligand into the frame of MOFs is described to achieve the first example of a MOF-based biosensor for the recognition and distinction of S-containing amino acids.

Metabolomic analysis of honey bee, Apis mellifera L. response to thiacloprid

The cyano-substituted neonicotinoid insecticide, thiacloprid, is nowadays widely used in agriculture for controlling insect pests. However, it also simultaneously has adverse effects on the health of important pollinators, such as honey bees. Previous studies have reported that sublethal doses of neonicotinoids impaired immunocompetence, learning and memory performance, and homing behaviour in honey bees. In the present study, using LC-MS-based combined with GC-MS-based metabolomic approaches, we profiled the metabolic changes that occur in the head of honey bee after subchronic exposure to 2 mg/L thiacloprid over 3 days. The estimated total dose of thiacloprid fed to each bee was 0.12 μg. The results showed that there were 115 metabolites significantly affected in thiacloprid-treated bees compared to control. The metabolites with high level of abundance enriched to wide range pathways associated with oxidative stress and detoxification suggest that the honey bees have activated their detoxification system to resistant toxicity of thiacloprid. While, the reduction of serotonin suggest thiacloprid may hinder the brain activity implicated in learning and behaviour development. Our study expand the understanding of the molecular basis of the complex interactions between neonicotinoids and honey bees.