Trichloroethanol, an active metabolite of chloral hydrate, modulates tetrodotoxin-resistant Na+ channels in rat nociceptive neurons

BACKGROUND

Chloral hydrate is a sedative-hypnotic drug widely used for relieving fear and anxiety in pediatric patients. However, mechanisms underlying the chloral hydrate-mediated analgesic action remain unexplored. Therefore, we investigated the effect of 2',2',2'-trichloroethanol (TCE), the active metabolite of chloral hydrate, on tetrodotoxin-resistant (TTX-R) Na⁺ channels expressed in nociceptive sensory neurons.

METHODS

The TTX-R Na⁺ current (I_Na) was recorded from acutely isolated rat trigeminal ganglion neurons using the whole-cell patch-clamp technique.

RESULTS

Trichloroethanol decreased the peak amplitude of transient TTX-R I_Na in a concentration-dependent manner and potently inhibited persistent components of transient TTX-R I_Na and slow voltage-ramp-induced I_Na at clinically relevant concentrations. Trichloroethanol exerted multiple effects on various properties of TTX-R Na⁺ channels; it (1) induced a hyperpolarizing shift on the steady-state fast inactivation relationship, (2) increased use-dependent inhibition, (3) accelerated the onset of inactivation, and (4) retarded the recovery of inactivated TTX-R Na⁺ channels. Under current-clamp conditions, TCE increased the threshold for the generation of action potentials, as well as decreased the number of action potentials elicited by depolarizing current stimuli.

CONCLUSIONS

Our findings suggest that chloral hydrate, through its active metabolite TCE, inhibits TTX-R I_Na and modulates various properties of these channels, resulting in the decreased excitability of nociceptive neurons. These pharmacological characteristics provide novel insights into the analgesic efficacy exerted by chloral hydrate.

Effect of trichloroethanol on TLR2 and TLR4/NF-κB-mediated antigen processing and presentation in HLA-B* 13:01-transfected antigen-presenting cells

Trichloroethanol (TCOH), as a metabolite of trichloroethylene, has sensitization in the pathogenesis of trichloroethylene-induced hypersensitivity dermatitis (TIHD) which the human leukocyte antigen (HLA)-B∗13:01 gene is strongly associated with it. However, it is still obscure how TCOH participates in the pathogenesis of TIHD. Here, we demonstrate that TLR2 and TLR4 signaling through MyD88 and TRAF6-dependent pathway could activate NF-κB by promoting degradation of the inhibitor IκB-α to stimulate the process of NF-κB nuclear translocation. Besides, the crucial molecules of antigen processing and presentation, including TAP1, LMP2, LMP7, and HLA-B* 13:01, were all enhanced and the abundance of HLA-B* 13:01 on the surface of CIR-B* 13:01 cells was also up-regulated with the TCOH concentration increasing. Notably, we used 50 μM pyrrolidinedithiocarbamate (ammonium) to effectively inhibit the activation of NF-κB, which could effectively reverse the stimulation of antigen processing and presentation in TCOH-treated CIR-B* 13:01 cells. Taken together, we speculated that TCOH could promote the abundance of HLA complex on the antigen-presenting cells via TLR2 and TLR4/NF-κB to induce the severe reactivation of T lymphocytes, leading to the extreme immune response.

[Simultaneous determination of trichloroethylene and trichloroethanol in blood by liquid-liquid extraction-gas chromatography]

Objective: To establish a method for determing the trichloroethylene(TCE)and trichloroethanol(TCOH)in blood samples by liquid-liquid extraction-gas chromatography with electron capture detector. Methods: With this method,ether was used as extraction solvent and trichloromethane was used as an internal standard. The whole blood sample was extracted with ether, and dehydrated by anhydrous sodium sulfate. Then the analytes were separated on HP-5 capillary column(30m×0.32mm×0.15μm)and detected byECD.The retention time was for qualitative analysis and the internal standard was for quantitation. Results: The standard curves of TCE and TCOH showed significant linearity between 95.5μg/L-7640.0μg/L(r=0.9997)and 19.0μg/L-1520.0μg/L(r=0.9992). The average recovery was 95.5%-103.6%.The intra-day and inter-day precisions(RSD)were 2.5%-6.8%(n=6)and 1.6%-4.3%(n=6) respectively. The detect limit of TCE and TCOH were 2.10 μg/L and 0.56μg/L(S/N=3)respectively.The blood can be kept 7 days at-20℃ refrigerator without significantly loss. Conclusion: This method is proved to be simple,practical and highly sensitive. It can satisfy the request for the determination of blood samples of humans exposed to TCE.

Fluorescent Protein Visualization Immediately After Gel Electrophoresis Using an In-Gel Trichloroethanol Photoreaction with Tryptophan

SDS-polyacrylamide gel electrophoresis (SDS-PAGE) is one of the essential techniques in molecular biology and biochemistry laboratories and requires rapid visualization methods for efficient sample analysis. Proteins on polyacrylamide gels can be visualized within 5 min via the photoreaction of tryptophan with trichloroethanol. This process does not require protein fixation, staining, or destaining. In this method polyacrylamide gels are prepared by adding trichloroethanol before polymerization. After electrophoresis, the gel is immediately activated on a standard UV transilluminator and the fluorescently labeled proteins are imaged. The reaction is based on the photoreaction of trichloroethanol with tryptophan residues within the protein. This generates a visible blue-green fluorescence (∼500 nm) that is accurately imaged. Here we describe the preparation of Tris-glycine and Tris-tricine SDS-polyacrylamide gels with trichloroethanol and the photoreaction and visualization of tryptophan containing proteins.