Cannabinoids ablate release of TNFα in rat microglial cells stimulated with lypopolysaccharide

Abstract

Upon activation, brain microglial cells release proinflammatory mediators, such as TNF␣, which may play an important role in eliciting neuroinflammatory processes causing brain damage. As cannabinoids have been reported to exert anti-inflammatory and neuroprotective actions in the brain, we here examined the effect of both synthetic and endogenous cannabinoids on TNF␣ release elicited by bacterial endotoxin lypopolysaccharide (LPS) in cultured microglia. Exposure of primary cultures of rat cortical microglial cells to LPS significantly stimulated TNF␣ mRNA expression and release. The endogenous cannabinoids anandamide and 2-arachidonylglycerol (2-AG), as well as the synthetic cannabinoids (ϩ)WIN 55,212-2, CP 55,940, and HU210, inhibited in a concentration-dependent manner (1-10 M) the LPS-induced TNF␣ release. Unlike the high-affinity cannabinoid receptor agonist (ϩ)WIN 55,212-2, the low-affinity stereoisomer (Ϫ)WIN 55,212-2 did not exert any significant inhibition on TNF␣ release. Given this stereoselectivity, the ability of (ϩ)WIN 55,212-2 to inhibit LPS-induced TNF␣ release from microglia is most likely receptor-mediated. By RT-PCR we found that the two G i/o protein-coupled cannabinoid receptors (type 1 and 2) are both expressed in microglial cultures. However, selective antagonists of type 1 (SR141716A and AM251) and type 2 (SR144528) cannabinoid receptors did not affect the effect of (ϩ)WIN 55,212-2. Consistent with this finding is the observation that the ablative effect of (ϩ)WIN 55,212-2 on LPS-evoked release of TNF␣ was not sensitive to the G i/o protein inactivator pertussis toxin. In addition, the cAMP elevating agents dibutyryl cAMP and forskolin both abolished LPS-induced TNF␣ release, thus rendering unlikely the possibility that (ϩ)WIN 55,212-2 could ablate TNF␣ release through the inhibition of adenylate cyclase via the G i -coupled cannabinoid receptors type 1 and 2. In summary, our data indicate that both synthetic and endogenous cannabinoids inhibit LPS-induced release of TNF␣ from microglial cells. By showing that such effect does not appear to be mediated by either CB receptor type 1 or 2, we provide evidence suggestive of the existence of yet unidentified cannabinoid receptor(s) in brain microglia. GLIA 41: 161-168, 2003.

Cannabinoid receptor stimulation is anti-inflammatory and improves memory in old rats

“…Two endogenous ligands for these receptors, arachydonylethanolamine and 2-arachidonoylglycerol (Stella, 2004), influence immune responses by inhibiting cytokine release and other anti-inflammatory actions (Klein et al, 2003;Klein, 2005). In vitro, microglia expresses CB receptors and release cytokines in response to exposure to LPS or beta-amyloid protein (Facchinetti et al, 2003;Ramirez et al, 2005;Sheng et al, 2005). Astrocytes may also synthesize and release endocannabinoids (Walter et al, 2002).…”

Cannabinoids and neuroinflammation

“…Primary cultures of rat and mouse microglia express both CB 1 and CB 2 receptor mRNA and protein (Sinha et al, 1998;Carlisle et al, 2002;Facchinetti et al, 2003;Walter et al, 2003a). Human microglia also express CB 2 receptor mRNA (Klegeris et al, 2003).…”

“…CP55940 inhibits NO production in IFN-g-and lipopolysaccharide-(LPS, a bacterial cell wall molecule) stimulated rat microglia (Waksman et al, 1999;Cabral et al, 2001). Primary cultures of rat microglia activated by LPS release TNFa, and this is inhibited by anandamide, 2-AG, WIN55212-2, CP55940, and HU210, but SR141716A, AM251, and SR144528 do not alter WIN55212-2 effects (Facchinetti et al, 2003). THC reduces IL-1b, IL-6, and TNFa production in LPS-stimulated rat microglia (Puffenbarger et al, 2000).…”

Prevention of Alzheimer's Disease Pathology by Cannabinoids: Neuroprotection Mediated by Blockade of Microglial Activation

“…In contrast, the CB 2 receptor is considered to be expressed solely in cells and organs of the immune system and is unrelated to cannabinoid psychoactivity. There are also recent reports on the existence of CB 2 receptors in microglia (Walter et al, 2003) and on cannabinoids affecting migration (Walter et al, 2003), as well as nitric oxide (NO) and cytokine production (Waksman et al, 1999;Puffenbarger et al, 2000;Facchinetti et al, 2003) in microglial cell cultures in vitro.…”