Specific patterns of spinal metabolites underlying α-Me-5-HT-evoked pruritus compared with histamine and capsaicin assessed by proton nuclear magnetic resonance spectroscopy

Abstract

The mechanism behind itching is not well understood. Proton nuclear magnetic resonance (H-NMR) spectroscopic analysis of spinal cord extracts provides a quick modality for evaluating the specific metabolic activity of α-Me-5-HT-evoked pruritus mice. In the current study, four groups of young adult male C57Bl/6 mice were investigated; one group treated with saline, while the other groups intradermally injected with α-Me-5-HT (histamine independent pruritogen), histamine (histamine dependent pruritogen) and capsaicin (algogenic substance), respectively. The intradermal microinjection of α-Me-5-HT and histamine resulted in a dramatic increase in the itch behavior. Furthermore, the results of NMR studies of the spinal cord extracts revealed that the metabolites show very different patterns for these different drugs, especially when comparing α-Me-5-HT and capsaicin. All the animals in the groups of α-Me-5-HT and capsaicin were completely separated using the metabolite parameters and principal component analysis. For α-Me-5-HT, the concentrations of glutamate, GABA, glycine and aspartate increased significantly, especially for GABA (increased 17.2%, p=0.008). Furthermore, the concentration of NAA increased, but there was no significant difference (increased 11.3%, p=0.191) compared to capsaicin (decreased 29.1%, p=0.002). Thus the application of magnetic resonance spectroscopy technique, coupled with statistical analysis, could further explain the mechanism behind itching evoked by α-Me-5-HT or other drugs. It can thus improve our understanding of itch pathophysiology and pharmacological therapies which may contribute to itch relief.

Altered expression of target genes of spinal cord in different itch models compared with capsaicin assessed by RT-qPCR validation

“…All pruritic behaviors were evaluated as previously described with minor modifications [ 6 , 43 , 44 ]. The tests of algogenic behavior by capsaicin were performed similar with previous researches [ 11 , 43 ].…”

“…It is well-known that GRPR-positive neurons in the spinal cord constitute a long-sought labeled line for itch not pain sensation [ 10 ]. In our previous research, the results of proton nuclear magnetic resonance ( 1 H-NMR) studies of the spinal cord extracts revealed that the metabolites showed very different patterns for pruritogen and algogenic substance [ 11 ]. Given the high prevalence of itch in some patients with skin diseases [ 12 – 14 ], it is pivotal to know whether the genes are dysregulated in the spinal cord in different itch models.…”

Proteomics and metabolomics analysis of hepatic mitochondrial metabolism in alcohol-preferring and non-preferring rats

“…For the study of metabolites, the liver samples were extracted with the same protocol as our former studies [ 35 , 36 ]. Here the procedure was briefly described.…”

Quantitative proteomics reveal the alterations in the spinal�cord after myocardial ischemia‑reperfusion injury in rats

“…Rapid advancements in high-throughput technologies and computational frameworks offer an excellent opportunity to quantify spinal nociception using neuronal activation induced by noxious stimuli. The author's previous study showed that transcriptomics and metabolomics enable the examination of spinal biological systems in unprecedented detail (32)(33)(34)(35)(36). More recently, different patterns were revealed in the metabolic and transcriptional levels of the thoracic spinal cord under myocardial ischemia-reperfusion injury (37)(38)(39).…”