Inhibition of glucosylceramide synthase reversibly decreases the capsaicin-induced activation and TRPV1 expression of cultured dorsal root ganglion neurons

Abstract

Recent studies have demonstrated significant changes in the neuronal ganglioside status associated with altered functional states of nociceptive primary sensory neurons. In the present study, therefore, the effects of the inhibition of glucosylceramide synthase, the key enzyme of ganglioside synthesis, were studied on chemically defined populations and on the activation of TRPV1 of cultured adult rat sensory ganglion neurons. In control cultures, capsaicin resulted in the activation of TRPV1 in 29.7+/-2.5% of the neurons, as assessed with the cobalt uptake assay. Pretreatment of the cultures for 4days with an inhibitor of glucosylceramide synthase, d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (d-PDMP), significantly decreased the proportion of capsaicin-activated neurons to 11.6+/-1.2%. Immunohistochemistry demonstrated that, in control cultures, 37.5+/-1.4% of the neurons displayed TRPV1 immunoreactivity, whereas in d-PDMP-treated cultures the proportion of TRPV1-immunoreactive neurons was diminished to 18.2+/-2.1%. Further experiments disclosed that these effects of d-PDMP were reversible. The capsaicin-, but not the high potassium-induced release of CGRP, was also significantly reduced after d-PDMP treatment, as measured with ELISA. The proportions of IB4- and CGRP-positive neurons were not significantly affected by d-PDMP. The present observations demonstrate that inhibition of neuronal ganglioside synthesis profoundly modulates the expression of the TRPV1 receptor, apparently leaving other markers of nociceptive neurons, such as CGRP and IB4, unaffected. The findings indicate that as yet unidentified ganglioside(s) synthesized by the glucosylceramide synthase pathway may be essential for nociception through mechanisms which may implicate membrane lipid raft function and/or altered nerve growth factor signaling, which are essential for the TRPV1 receptor function.

Bioactive Sphingolipids in Response to Chemotherapy: A Scope on Leukemias

“…GluCer is not only important for conferring chemotherapeutic resistance to cancer cells, but it is also important for the pathophysiology of several disorders including Gaucher disease, polycystic kidney disease and asthma [83][84][85]. Membrane trafficking, natural killer lymphocyte polarization and neuronal activation can be given as examples of other cellular processes involving GluCer [86][87][88].…”

Capsaicin-induced activation and chemical injury of nociceptive primary sensory neurons

“…Deprivation of NGF resulted in the elimination of neuronal capsaicin sensitivity of cultured DRG neurons (Sántha et al, 2010;Winter et al, 1988). Moreover, capsaicin sensitivity (Jancsó, 1992;Jancsó and Ambrus, 1994;Jancsó et al, 1997) and TRPV1…”

Investigation of the transient receptor potential vanilloid 1 (TRPV1) ion channel

“…The response of TRPV1 to heat can be modified by tyrosine kinases or G-protein-coupled receptors. Channel activation can occur even at normal body temperatures [74,83,105]. Reducing agents such as dithiothreitol (DTT) strongly increase the thermally induced activity of the TRPV1 channel.…”

“…Inflammatory agents such as bradykinin, serotonin, histamine or prostaglandins can further stimulate TRPV1 activity, either by PKC-dependent pathways [105,107,108], by releasing the channel from PIP2-dependent inhibition [91,109], by a PKA-mediated recovery from inactivation [110], or by the formation of 12-HPETE [74,111].…”

“…Cell lines expressing TRPV1 ectopically -The HaCaT keratinocyte cell line was a kind gift of Prof. B. Farkas (Department of Dermatology, University of Cologne, Federal Republic of Germany) [105]. The COS-7 (CRL-1651) and BALB/c-3T3 (CCL-163) cell lines were obtained from ATCC.…”