Modulation of nociception and inflammation by sulfide in rheumatoid arthritis and activation of transient receptor potential ankyrin 1 (TRPA1) ion channels by sulfide compounds are well documented. The present study aims to investigate TRPA1-mediated effects of sulfide donor GYY4137 in K/BxN serum-transfer arthritis, a rodent model of rheumatoid arthritis. TRPA1 and somatostatin sst4 receptor wild-type (WT) and knockout mice underwent K/BxN serum transfer and were treated daily with GYY4137. Functional and biochemical signs of inflammation were recorded, together with histological characterization. These included detection of hind paw mechanical hyperalgesia by dynamic plantar esthesiometry, hind paw volume by plethysmometry, and upside-down hanging time to failure. Hind paw erythema, edema, and passive movement range of tibiotarsal joints were scored. Somatostatin release from sensory nerve endings of TRPA1 wild-type and knockout mice in response to polysulfide was detected by radioimmunoassay. Polysulfide formation from GYY4137 was uncovered by cold cyanolysis. GYY4137 aggravated mechanical hyperalgesia in TRPA1 knockout mice but ameliorated it in wild-type ones. Arthritis score was lowered by GYY4137 in TRPA1 wild-type animals. Increased myeloperoxidase activity, plasma extravasation, and subcutaneous MIP-2 levels of hind paws were detected in TRPA1 knockout mice upon GYY4137 treatment. Genetic lack of sst4 receptors did not alter mechanical hyperalgesia, edema formation, hanging performance, arthritis score, plasma extravasation, or myeloperoxidase activity. TRPA1 WT animals exhibited smaller cartilage destruction upon GYY4137 administration. Sodium polysulfide caused TRPA1-dependent somatostatin release from murine nerve endings. Sulfide released from GYY4137 is readily converted into polysulfide by hypochlorite. Polysulfide potently activates human TRPA1 receptors expressed in Chinese hamster ovary (CHO) cells. According to our data, the protective effect of GYY4137 is mediated by TRPA1, while detrimental actions are independent of the ion channel in the K/BxN serum-transfer arthritis model in mice. At acidic pH in inflamed tissue sulfide is released from GYY4137 and reacts with neutrophil-derived hypochlorite. Resulting polysulfide might be responsible for TRPA1-mediated antinociceptive and anti-inflammatory as well as TRPA1-independent pro-inflammatory effects.

No abstract

Somatostatin receptor subtype 4 (SST4) has been shown to mediate analgesic, antidepressant and anti-inflammatory functions without endocrine actions; therefore, it is proposed to be a novel target for drug development. To overcome the species differences of SST4 receptor expression and function between humans and mice, we generated an SST4 humanized mouse line to serve as a translational animal model for preclinical research. A transposon vector containing the hSSTR4 and reporter gene construct driven by the hSSTR4 regulatory elements were created. The vector was randomly inserted in Sstr4-deficient mice. hSSTR4 expression was detected by bioluminescent in vivo imaging of the luciferase reporter predominantly in the brain. RT-qPCR confirmed the expression of the human gene in the brain and various peripheral tissues consistent with the in vivo imaging. RNAscope in situ hybridization revealed the presence of hSSTR4 transcripts in glutamatergic excitatory neurons in the CA1 and CA2 regions of the hippocampus; in the GABAergic interneurons in the granular layer of the olfactory bulb and in both types of neurons in the primary somatosensory cortex, piriform cortex, prelimbic cortex and amygdala. This novel SST4 humanized mouse line might enable us to investigate the differences of human and mouse SST4 receptor expression and function and assess the effects of SST4 receptor agonist drug candidates.

Transient receptor potential ankyrin 1 (TRPA1) receptors are non-selective cation channels responsive to a variety of exogenous irritants and endogenous stimuli including products of oxidative stress. It is mainly expressed by primary sensory neurons; however, expression of TRPA1 by astrocytes and oligodendrocytes has recently been detected in the mouse brain. Genetic deletion of TRPA1 was shown to attenuate cuprizone-induced oligodendrocyte apoptosis and myelin loss in mice.In the present study we aimed at investigating mGFAP-Cre conditional TRPA1 knockout mice in the cuprizone model. These animals were generated by crossbreeding GFAP-Cre +/− and floxed TRPA1 (TRPA1 Fl/Fl ) mice. Cuprizone was administered for 6 weeks and demyelination was followed by magnetic resonance imaging (MRI). At the end of the treatment, demyelination and glial activation was also investigated by histological methods. The results of the MRI showed that demyelination was milder at weeks 3 and 4 in both homozygous (GFAP-Cre +/− TRPA1 Fl/Fl ) and heterozygous (GFAP-Cre +/− TRPA1 Fl/− ) conditional knockout animals compared to Cre −/− control mice. However, by week 6 of the treatment the difference was not detectable by either MRI or histological methods. In conclusion, TRPA1 receptors on astrocytes may transiently contribute to the demyelination induced by cuprizone, however, expression and function of TRPA1 receptors by other cells in the brain (oligodendrocytes, microglia, neurons) warrant further investigation.Cells 2020, 9, 81 2 of 13 and oxidized lipid molecules [1][2][3]. Apart from being a nocisensor for exogenous irritant compounds, it has been suggested to work as a sensor for oxidative stress [4]. Originally described to be localized on a subgroup of nociceptive primary afferent neurons [5,6], it was later revealed that TRPA1 is also expressed at lower levels by various non-neuronal cells including keratinocytes, endothelial cells and cells of the gastrointestinal mucosa [1-3,7]. More importantly, several studies have supported the presence of TRPA1 receptors in the brain on astrocytes [8][9][10], as well as oligodendrocytes [11]. A recent cell-specific transcriptome analysis of the mouse cortex revealed low level expression of TRPA1 on neurons, astrocytes, oligodendrocytes and microglia, as well [12].In astrocytes, TRPA1 receptors were implicated in both physiological and pathophysiological processes. Astrocyte TRPA1 receptors were shown to regulate resting Ca 2+ levels and modulate GABA-ergic inhibitory transmission by reducing GABA transport [8]. TRPA1 receptors on astrocytes were also suggested to play a role in long-term potentiation in the mouse hippocampus [9]. Since reactive astrocytes can contribute to the progression of neuroinflammation in neurodegenerative diseases [13,14], several workgroups, including ours, had started to investigate the role of TRPA1 in animal models of neurodegenerative diseases. Our previous study aimed at examining the role of TRPA1 in the cuprizone-induced demyelination model in mice. Cuprizone...

Background Pigment epithelium-derived factor (PEDF) is a serin protease inhibitor and a potent inhibitor of angiogenesis. Its serum level has significant associations with metabolic parameters. However, little is known about the association between PEDF levels and lipid parameters in renal transplanted (TX) patients. Therefore, our aim was to investigate the relationship between PEDF level and lipid parameters in TX patients. Methods Seventy TX patients (47 males, 23 females, mean age 51.7 ± 12.4 years) and 34 healthy controls were enrolled. We examined the serum creatinine, C-reactive protein, fasting glucose and lipid parameters right before, then 1 and 6 months after TX. High-density lipoprotein (HDL)-associated paraoxonase-1 (PON1) activities were measured spectrophotometrically. Lipoprotein subfractions were determined by Lipoprint. PEDF and oxidized low-density liporotein (oxLDL) levels were measured by ELISA. Results Before transplantation, patients had had a significantly higher PEDF level compared to control subjects ( p < 0.001). One month after transplantation, their PEDF level decreased significantly reaching the healthy controls’ level, and this lower level was maintained during the 6 months follow-up period as well. The initial oxLDL level was significantly higher, while PON1 activities were significantly lower in the patient group compared to the control group. We found a significant positive correlation between PEDF and total cholesterol, low-density lipoprotein (LDL)-cholesterol, triglyceride, oxLDL and small HDL subfraction; while negative correlations were found between PEDF and mean LDL size and large HDL subfraction during the entire follow-up period. Conclusion PEDF may play an important role in the increased oxidative stress and enhanced atherogenesis in renal transplant patients.