Inhibition of phosphatidylinositol-3 kinase γ reduces pruriceptive, inflammatory, and nociceptive responses induced by trypsin in mice

Abstract

This study investigated the effects of pharmacological inhibition of phosphatidylinositol 3-kinase (PI3K)γ in the pruriceptive, inflammatory, and nociceptive responses induced by trypsin in mice. The animals were orally treated with the selective PI3Kγ inhibitor AS605240 (0.3-30 mg/kg) 30 minutes beforehand. In separate groups, AS605240 was given by intrathecal (i.t.) or intracerebroventricular (i.c.v.) routes. The control groups received saline at the same schedules. The effects of PI3K blocking were assessed in different experimental assays. The oral treatment with AS605240 produced a marked reduction of scratching behavior elicited by trypsin. Moreover, AS605240 (1mg/kg) was able to produce a partial but significant inhibition of the scratching bouts elicited by CP 48/80. Interestingly, the i.c.v. and i.t. injection of AS605240 also reduced trypsin-induced itching. The oral administration of AS605240 was found effective in producing a significant and dose-dependent reduction of trypsin-induced paw edema and tumor necrosis factor α production, as well as the neutrophil recruitment, according to myeloperoxidase activity assessment. Likewise, oral AS605240 (1mg/kg) promoted a significant reduction of spontaneous nociception induced by trypsin in the mouse paw. In contrast, the oral administration of AS605240 did not significantly modify capsaicin-evoked nociception, although this inhibitor was effective when dosed by i.c.v. route. Noteworthy, AS605240 (1mg/kg) was able to prevent c-Fos and phospho-Akt immunopositivity at the spinal cord of trypsin-injected mice, either into the back of the neck or the paws. To conclude, PI3Kγ inhibition might well represent a valuable alternative for treating inflammatory and painful conditions, as well as pruritus.

Differential distribution of PI3K isoforms in spinal cord and dorsal root ganglia: Potential roles in acute inflammatory pain

“…However, i.t. injection of more than three times as much of the γ antagonist as used in this study elicited no change in either trypsin-induced nociception or pruritis [33], supporting the lack of spinal PI3Kγ staining and the negative behavioral results with i.t. injection that we observed.…”

Construction of a Global Pain Systems Network Highlights Phospholipid Signaling as a Regulator of Heat Nociception

“…To this end we focused our first efforts on phosphatidylinositol signaling, one of the major nodes predicted from the pain systems map, and a heat pain precedented pathway. Phosphatidylinositol signaling has been implicated in heat nociception and regulation of TRPV1 by multiple groups [11], [13], [16], [18], however its precise role has been controversial [16], [18], [23], and the specific participation of different phospholipid kinases has never been evaluated genetically, which we now decided to do.…”

“…Phosphatidylinositol signaling is a second messenger cascade involving the sequential phosphorylation of phosphatidylinositol 4-phosphate (PIP) to generate phosphatidylinositol 4,5-bisphosphate (PIP2) via PIP5' kinases (phosphatidylinositol-5-OH kinase; PIP5K), and then phosphorylation of PIP2 via PI3 kinases (phosphatidylinositol-3-OH kinase; PI3K) to generate phosphatidylinositol 3,4,5-trisphosphate (PIP3). In mammalian systems phospholipid signaling has been implicated in regulating pain perception [11]–[13], TRPV1 function [14]–[21], and itch [22], but how phosphatidylinositol signaling is involved in mammalian nociception is controversial, with data suggesting for example that PIP2 may either increase or decrease TRPV1 function [23], [24]. Based on the suggested involvement of phospholipid signaling in our conserved functional pain network, and in context of the controversial role for phosphatidylinositol signaling in pain perception, we employed genetic approaches to evaluate the role of phosphatidylinositol signaling in mammalian nociception.…”

Synergistic Effects of Celecoxib and Bupropion in a Model of Chronic Inflammation-Related Depression in Mice

“…The expression of COX-2 was measured by immunohistochemistry, as previously described by [38]. The whole brains were rapidly excised 14 days after CFA injection and fixed in buffered neutral formalin.…”