TY  - JOUR
AU  - Funk, K.
AU  - Woitecki, A.
AU  - Franjic-Würtz, C.
AU  - Gensch, T.
AU  - Möhrlen, F.
AU  - Frings, S.
TI  - Modulation of chloride homeostasis by inflammatory mediators in dorsal root ganglion neurons
JO  - Molecular pain
VL  - 4
SN  - 1744-8069
CY  - London
PB  - BioMed Central
M1  - PreJuSER-238
SP  - 32 - 43
PY  - 2008
N1  - This work was supported by the Deutsche Forschungsgemeinschaft (Fr 937/6).
AB  - Chloride currents in peripheral nociceptive neurons have been implicated in the generation of afferent nociceptive signals, as Cl- accumulation in sensory endings establishes the driving force for depolarizing, and even excitatory, Cl- currents. The intracellular Cl- concentration can, however, vary considerably between individual DRG neurons. This raises the question, whether the contribution of Cl- currents to signal generation differs between individual afferent neurons, and whether the specific Cl- levels in these neurons are subject to modulation. Based on the hypothesis that modulation of the peripheral Cl- homeostasis is involved in the generation of inflammatory hyperalgesia, we examined the effects of inflammatory mediators on intracellular Cl- concentrations and on the expression levels of Cl- transporters in rat DRG neurons.We developed an in vitro assay for testing how inflammatory mediators influence Cl- concentration and the expression of Cl- transporters. Intact DRGs were treated with 100 ng/ml NGF, 1.8 microM ATP, 0.9 microM bradykinin, and 1.4 microM PGE2 for 1-3 hours. Two-photon fluorescence lifetime imaging with the Cl--sensitive dye MQAE revealed an increase of the intracellular Cl- concentration within 2 hours of treatment. This effect coincided with enhanced phosphorylation of the Na+-K+-2Cl- cotransporter NKCC1, suggesting that an increased activity of that transporter caused the early rise of intracellular Cl- levels. Immunohistochemistry of NKCC1 and KCC2, the main neuronal Cl- importer and exporter, respectively, exposed an inverse regulation by the inflammatory mediators. While the NKCC1 immunosignal increased, that of KCC2 declined after 3 hours of treatment. In contrast, the mRNA levels of the two transporters did not change markedly during this time. These data demonstrate a fundamental transition in Cl- homeostasis toward a state of augmented Cl- accumulation, which is induced by a 1-3 hour treatment with inflammatory mediators.Our findings indicate that inflammatory mediators impact on Cl- homeostasis in DRG neurons. Inflammatory mediators raise intracellular Cl- levels and, hence, the driving force for depolarizing Cl- efflux. These findings corroborate current concepts for the role of Cl- regulation in the generation of inflammatory hyperalgesia and allodynia. As the intracellular Cl- concentration rises in DRG neurons, afferent signals can be boosted by excitatory Cl- currents in the presynaptic terminals. Moreover, excitatory Cl- currents in peripheral sensory endings may also contribute to the generation or modulation of afferent signals, especially in inflamed tissue.
KW  - Adenosine Triphosphate: pharmacology
KW  - Animals
KW  - Bradykinin: pharmacology
KW  - Chlorides: metabolism
KW  - Dinoprostone: pharmacology
KW  - Ganglia, Spinal: cytology
KW  - Ganglia, Spinal: drug effects
KW  - Ganglia, Spinal: metabolism
KW  - Homeostasis: drug effects
KW  - Homeostasis: physiology
KW  - Inflammation Mediators: pharmacology
KW  - Nerve Growth Factors: pharmacology
KW  - Neurons: drug effects
KW  - Neurons: metabolism
KW  - Organ Culture Techniques
KW  - Rats
KW  - Chlorides (NLM Chemicals)
KW  - Inflammation Mediators (NLM Chemicals)
KW  - Nerve Growth Factors (NLM Chemicals)
KW  - Dinoprostone (NLM Chemicals)
KW  - Adenosine Triphosphate (NLM Chemicals)
KW  - Bradykinin (NLM Chemicals)
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
C6  - pmid:18700020
C2  - pmc:PMC2526990
UR  - <Go to ISI:>//WOS:000258959400001
DO  - DOI:10.1186/1744-8069-4-32
UR  - https://juser.fz-juelich.de/record/238
ER  -