Sulfasalazine blocks the development of tactile allodynia in diabetic rats.
OBJECTIVE
Diabetic neuropathy is manifested either by loss of nociception (painless syndrome) or by mechanical hyperalgesia and tactile allodynia (pain in response to nonpainful stimuli). While therapies with vasodilators or neurotrophins reverse some functional and metabolic abnormalities in diabetic nerves, they only partially ameliorate neuropathic pain. The reported link between nociception and targets of the anti-inflammatory drug sulfasalazine prompted us to investigate its effect on neuropathic pain in diabetes.


METHODS
We examined the effects of sulfasalazine, salicylates, and the poly(ADP-ribose) polymerase-1 inhibitor PJ34 on altered nociception in streptozotocin-induced diabetic rats. We also evaluated the levels of sulfasalazine targets in sciatic nerves and dorsal root ganglia (DRG) of treated animals. Finally, we analyzed the development of tactile allodynia in diabetic mice lacking expression of the sulfasalazine target nuclear factor-kappaB (NF-kappaB) p50.


RESULTS
Sulfasalazine completely blocked the development of tactile allodynia in diabetic rats, whereas relatively minor effects were observed with other salicylates and PJ34. Along with the behavioral findings, sciatic nerves and DRG from sulfasalazine-treated diabetic rats displayed a decrease in NF-kappaB p50 expression compared with untreated diabetic animals. Importantly, the absence of tactile allodynia in diabetic NF-kappaB p50(-/-) mice supported a role for NF-kappaB in diabetic neuropathy. Sulfasalazine treatment also increased inosine levels in sciatic nerves of diabetic rats.


CONCLUSIONS
The complete inhibition of tactile allodynia in experimental diabetes by sulfasalazine may stem from its ability to regulate both NF-kappaB and inosine. Sulfasalazine might be useful in the treatment of nociceptive alterations in diabetic patients.
Berti-Mattera
Liliana N
LN
Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA. lnb@case.edu
Kern
Timothy S
TS
Siegel
Ruth E
RE
Nemet
Ina
I
Mitchell
Rochanda
R
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000150:complications*; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism; D015151:Immunoblotting; D007288:Inosine / Q000378:metabolism; D052002:NF-kappa B p50 Subunit / Q000378:metabolism; D010146:Pain / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D010147:Pain Measurement; D010616:Phenanthrenes / Q000494:pharmacology; D051381:Rats; D012459:Salicylates / Q000494:pharmacology; D012584:Sciatic Nerve / Q000187:drug effects / Q000378:metabolism; D012460:Sulfasalazine / Q000494:pharmacology*; D053719:Tandem Mass Spectrometry
D000894:Anti-Inflammatory Agents, Non-Steroidal; D001786:Blood Glucose; C434926:N-(oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide hydrochloride; D052002:NF-kappa B p50 Subunit; D010616:Phenanthrenes; D012459:Salicylates; D012460:Sulfasalazine; D007288:Inosine