HU 308

HU-308 is a selective agonist of CB2-receptor with a Ki value of 20 nM. The Ki value for CB1-receptor is >10 µM.
Cannabinoid 2 receptor (CB2-receptor) belongs to the seven transmembranes G protein-coupled receptor superfamily. It is mainly distributed in peripheral tissue associated with immune functions.
In HLSECs, HU-308 markedly reduced the expression of both ICAM-1 and VCAM-1, which was induced by TNFα. HU-308 attenuated TNF- treatment induced RhoA activation (4.0-fold vs. control) and NF-B Activation. HU-308 inhibited TNFα-induced monocyte adhesion in aortas ex vivo [1].
HU-308 increased both primary neurosphere generation and neural progenitor self-renewal. HU-308 increased the number of BrdU incorporating cells in a CB2-dependent manner. HU-308 stimulated ERK and Akt [2].
Pretreatment of mice with HU-308 decreases the I/R-induced tissue damage, inflammatory cell infiltration, tissue and serum TNF-α, MIP-1, and MIP-2 levels, tissue lipid peroxidation and apoptosis [3].
References:
1.Rajesh M, Mukhopadhyay P, Bátkai S, et al. CB2-receptor stimulation attenuates TNF-alpha-induced human endothelial cell activation, transendothelial migration of monocytes, and monocyte-endothelial adhesion. Am J Physiol Heart Circ Physiol. 2007 Oct;293(4):H2210-8.
2.Palazuelos J, Aguado T, Egia A, et al. Non-psychoactive CB2 cannabinoid agonists stimulate neural progenitor proliferation. FASEB J. 2006 Nov;20(13):2405-7.
3.Rajesh M, Pan H, Mukhopadhyay P, et al. Cannabinoid-2 receptor agonist HU-308 protects against hepatic ischemia/reperfusion injury by attenuating oxidative stress, inflammatory response, and apoptosis. J Leukoc Biol. 2007 Dec;82(6):1382-9.

CB2 cannabinoid receptor agonist enantiomers HU-433 and HU-308: An inverse relationship between binding affinity and biological potency.[Pubmed:26124120]

Proc Natl Acad Sci U S A. 2015 Jul 14;112(28):8774-9.

Activation of the CB2 receptor is apparently an endogenous protective mechanism. Thus, it restrains inflammation and protects the skeleton against age-related bone loss. However, the endogenous cannabinoids, as well as Delta(9)-tetrahydrocannabinol, the main plant psychoactive constituent, activate both cannabinoid receptors, CB1 and CB2. HU-308 was among the first synthetic, selective CB2 agonists. HU-308 is antiosteoporotic and antiinflammatory. Here we show that the HU-308 enantiomer, designated HU-433, is 3-4 orders of magnitude more potent in osteoblast proliferation and osteoclast differentiation culture systems, as well as in mouse models, for the rescue of ovariectomy-induced bone loss and ear inflammation. HU-433 retains the HU-308 specificity for CB2, as shown by its failure to bind to the CB1 cannabinoid receptor, and has no activity in CB2-deficient cells and animals. Surprisingly, the CB2 binding affinity of HU-433 in terms of [(3)H]CP55,940 displacement and its effect on [(35)S]GTPgammaS accumulation is substantially lower compared with HU-308. A molecular-modeling analysis suggests that HU-433 and -308 have two different binding conformations within CB2, with one of them possibly responsible for the affinity difference, involving [(35)S]GTPgammaS and cAMP synthesis. Hence, different ligands may have different orientations relative to the same binding site. This situation questions the usefulness of universal radioligands for comparative binding studies. Moreover, orientation-targeted ligands have promising potential for the pharmacological activation of distinct processes.

Cannabinoid-2 receptor agonist HU-308 protects against hepatic ischemia/reperfusion injury by attenuating oxidative stress, inflammatory response, and apoptosis.[Pubmed:17652447]

J Leukoc Biol. 2007 Dec;82(6):1382-9.

In this study, we have investigated the role of the cannabinoid CB(2) (CB(2)) receptor in an in vivo mouse model of hepatic ischemia/reperfusion (I/R) injury. In addition, we have assessed the role of the CB(2) receptor in TNF-alpha-induced ICAM-1 and VCAM-1 expression in human liver sinusoidal endothelial cells (HLSECs) and in the adhesion of human neutrophils to HLSECs in vitro. The potent CB(2) receptor agonist HU-308, given prior to the induction of I/R, significantly attenuated the extent of liver damage (measured by serum alanine aminotransferase and lactate dehydrogenase) and decreased serum and tissue TNF-alpha, MIP-1alpha, and MIP-2 levels, tissue lipid peroxidation, neutrophil infiltration, DNA fragmentation, and caspase 3 activity. The protective effect of HU-308 against liver damage was also preserved when given right after the ischemic episode. HU-308 also attenuated the TNF-alpha-induced ICAM-1 and VCAM-1 expression in HLSECs, which expressed CB(2) receptors, and the adhesion of human neutrophils to HLSECs in vitro. These findings suggest that selective CB(2) receptor agonists may represent a novel, protective strategy against I/R injury by attenuating oxidative stress, inflammatory response, and apoptosis.

Anti-Inflammatory and Osteoprotective Effects of Cannabinoid-2 Receptor Agonist HU-308 in a Rat Model of Lipopolysaccharide-Induced Periodontitis.[Pubmed:26846967]

J Periodontol. 2016 Jun;87(6):725-34.

BACKGROUND: Anti-inflammatory and immunologic properties of cannabinoids have been reported in several tissues. Expression of cannabinoid receptor Type 2 was reported in osteoblasts and osteoclasts, suggesting a key role in bone metabolism. The aim of this study is to assess the effect of treatment with cannabinoid-2 receptor agonist HU-308 in the oral health of rats subjected to lipopolysaccharide (LPS)-induced periodontitis. METHODS: Twenty-four rats were distributed in four groups (six rats per group): 1) control rats; 2) sham rats; 3) rats submitted to experimental periodontitis (LPS); and 4) rats submitted to experimental periodontitis and treated with HU-308 (LPS+HU). In groups LPS and LPS+HU, periodontitis was induced by LPS (1 mg/mL) injected into the gingival tissue (GT) of maxillary and mandibular first molars and into the interdental space between the first and second molars, 3 days per week for 6 weeks. In group LPS+HU, HU-308 (500 ng/mL) was applied topically to the GT daily. RESULTS: Alveolar bone loss resulting from LPS-induced periodontitis was significantly attenuated with HU-308 treatment (LPS+HU), measured by macroscopic and histologic examination. Treatment also reduced gingival production of inflammatory mediators augmented in LPS-injected rats, such as: 1) inducible nitric oxide (iNOS) activity (LPS: 90.18 +/- 36.51 pmol/minute/mg protein versus LPS+HU: 16.37 +/- 4.73 pmol/minute/mg protein; P <0.05); 2) tumor necrosis factor alpha (LPS: 185.70 +/- 25.63 pg/mg protein versus LPS+HU: 95.89 +/- 17.47 pg/mg protein; P <0.05); and 3) prostaglandin E2 (PGE2) (LPS: 159.20 +/- 38.70 pg/mg wet weight versus LPS+HU: 71.25 +/- 17.75 pg/mg wet weight; P <0.05). Additionally, HU-308 treatment prevented the inhibitory effect of LPS-induced periodontitis on the salivary secretory response to pilocarpine. Moreover, iNOS activity and PGE2 content, which were increased by LPS-induced periodontitis in the submandibular gland, returned to control values after HU-308 treatment. CONCLUSION: This study demonstrates anti-inflammatory, osteoprotective, and prohomeostatic effects of HU-308 in oral tissues of rats with LPS-induced periodontitis.

Microglial CB2 cannabinoid receptors are neuroprotective in Huntington's disease excitotoxicity.[Pubmed:19805493]

Brain. 2009 Nov;132(Pt 11):3152-64.

Cannabinoid-derived drugs are promising agents for the development of novel neuroprotective strategies. Activation of neuronal CB(1) cannabinoid receptors attenuates excitotoxic glutamatergic neurotransmission, triggers prosurvival signalling pathways and palliates motor symptoms in animal models of neurodegenerative disorders. However, in Huntington's disease there is a very early downregulation of CB(1) receptors in striatal neurons that, together with the undesirable psychoactive effects triggered by CB(1) receptor activation, foster the search for alternative pharmacological treatments. Here, we show that CB(2) cannabinoid receptor expression increases in striatal microglia of Huntington's disease transgenic mouse models and patients. Genetic ablation of CB(2) receptors in R6/2 mice, that express human mutant huntingtin exon 1, enhanced microglial activation, aggravated disease symptomatology and reduced mice lifespan. Likewise, induction of striatal excitotoxicity in CB(2) receptor-deficient mice by quinolinic acid administration exacerbated brain oedema, microglial activation, proinflammatory-mediator state and medium-sized spiny neuron degeneration. Moreover, administration of CB(2) receptor-selective agonists to wild-type mice subjected to excitotoxicity reduced neuroinflammation, brain oedema, striatal neuronal loss and motor symptoms. Studies on ganciclovir-induced depletion of astroglial proliferation in transgenic mice expressing thymidine kinase under the control of the glial fibrillary acidic protein promoter excluded the participation of proliferating astroglia in CB(2) receptor-mediated actions. These findings support a pivotal role for CB(2) receptors in attenuating microglial activation and preventing neurodegeneration that may pave the way to new therapeutic strategies for neuroprotection in Huntington's disease as well as in other neurodegenerative disorders with a significant excitotoxic component.

Cannabinoid CB2 receptor agonist activity in the hindpaw incision model of postoperative pain.[Pubmed:16316653]

Eur J Pharmacol. 2005 Dec 19;527(1-3):172-4.

The identification of peripherally expressed CB2 receptors and reports that the selective activation of cannabinoid CB2 receptors produces antinociception without traditional cannabinergic side effects suggests that selective cannabinoid CB2 receptor agonists might be useful in the management of pain. In a rat hindpaw incision model, we examined the antiallodynic activity of the selective cannabinoid CB2 receptor agonists AM1241 (3-30 mg/kg i.p.), GW405833 (3-30 mg/kg i.p.), and HU-308 (0.3-30 mg/kg i.p.). The rank order for efficacy in the hindpaw incision model following a dose of 10 mg/kg, i.p. was AM1241 > GW405833 = HU-308, and the selective cannabinoid CB2 receptor antagonist, SR144528, reversed the antiallodynic effect of HU-308. Together, these data suggest that selective cannabinoid CB2 receptor agonists might represent a new class of postoperative analgesics.

HU-308: a specific agonist for CB(2), a peripheral cannabinoid receptor.[Pubmed:10588688]

Proc Natl Acad Sci U S A. 1999 Dec 7;96(25):14228-33.

Two cannabinoid receptors have been identified: CB(1), present in the central nervous system (CNS) and to a lesser extent in other tissues, and CB(2), present outside the CNS, in peripheral organs. There is evidence for the presence of CB(2)-like receptors in peripheral nerve terminals. We report now that we have synthesized a CB(2)-specific agonist, code-named HU-308. This cannabinoid does not bind to CB(1) (K(i) > 10 microM), but does so efficiently to CB(2) (K(i) = 22.7 +/- 3.9 nM); it inhibits forskolin-stimulated cyclic AMP production in CB(2)-transfected cells, but does so much less in CB(1)-transfected cells. HU-308 shows no activity in mice in a tetrad of behavioral tests, which together have been shown to be specific for tetrahydrocannabinol (THC)-type activity in the CNS mediated by CB(1). However, HU-308 reduces blood pressure, blocks defecation, and elicits anti-inflammatory and peripheral analgesic activity. The hypotension, the inhibition of defecation, the anti-inflammatory and peripheral analgesic effects produced by HU-308 are blocked (or partially blocked) by the CB(2) antagonist SR-144528, but not by the CB(1) antagonist SR-141716A. These results demonstrate the feasibility of discovering novel nonpsychotropic cannabinoids that may lead to new therapies for hypertension, inflammation, and pain.