SAG

Smoothened Agonist (SAG, CAS No. 912545-86-9) is a potent Smoothened (Smo) receptor agonist. Its core biological functions include activating the Hedgehog (Hh) signaling pathway, promoting myelin regeneration, improving mitochondrial function and neuroprotection, inducing embryonic developmental abnormalities, and exhibiting sex-dependent effects in immune regulation. Its target is the Smo receptor (specific activation; by binding to its transmembrane domain to relieve inhibition by the Patched (Ptch) receptor, thereby initiating downstream gene expression such as Gli1 and Ptch1). Related functional activity is evaluated by downstream pathway molecule expression or phenotypic changes.

Animal modeling includes both disease induction and model treatment applications: for induction, intraperitoneal injection of 25 mg/kg in pregnant mice at E10.5 can establish mouse models of cleft tongue and craniofacial malformations (mimicking the pathological state of excessive Hh pathway activation); for treatment, it is used in models such as experimental autoimmune encephalomyelitis (EAE), Friedreich’s ataxia (FRDA), demyelination, and glucocorticoid-induced neonatal cerebellar injury, exerting myelin regeneration, neuroprotective, and anti-inflammatory effects.

Common applications and concentrations: in cell culture, Shh Light II cells, C3H10T1/2 cells, and human astrocytes (HAs) commonly use 1 μM (for pathway activation, mitochondrial function improvement, etc.); in ShhN-stimulated cell models, 20 nM can be used for pathway rescue experiments. In animal experiments, commonly used doses for model treatment are oral 15 mg/kg, intraperitoneal injection 20-25 mg/kg, and intranasal administration 0.1-0.3 mg / day; the teratogenic induction dose in pregnant mice is 25 mg/kg. There is no direct clinical application concentration. Effects corresponding to effective treatment concentrations: at the animal level, 1 μM (cells) can activate the Hh pathway and improve mitochondrial function and lipid droplet accumulation in FRDA model astrocytes; 20-25 mg/kg (animals) can alleviate demyelination and neurological deficits in the EAE model and prevent glucocorticoid-induced cerebellar injury; intranasal administration of 0.3 mg / day can promote oligodendrocyte progenitor cell proliferation and differentiation in demyelination models. Regarding sex dependence, in female EAE models, use alone may enhance peripheral inflammation (increasing NK cell proportion and cytokine levels), and combination with testosterone can offset this effect.

References:

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[2] Vicente-Acosta A, Giménez-Cassina A, Díaz-Nido J, Loria F. The smoothened agonist SAG reduces mitochondrial dysfunction and neurotoxicity of frataxin-deficient astrocytes. J Neuroinflammation. 2022 Apr 12;19(1):93. doi: 10.1186/s12974-022-02442-w. PMID: 35413853; PMCID: PMC9006607.

[3] Luo J, Wang J, Yang J, Huang W, Liu J, Tan W, Xin H. Saikosaponin B1 and Saikosaponin D inhibit tumor growth in medulloblastoma allograft mice via inhibiting the Hedgehog signaling pathway. J Nat Med. 2022 Jun;76(3):584-593. doi: 10.1007/s11418-022-01603-8. Epub 2022 Feb 16. PMID: 35171398.

[4] Kassoussi A, Zahaf A, Hutteau-Hamel T, Mattern C, Schumacher M, Bobé P, Traiffort E. The Smoothened agonist SAG Modulates the Male and Female Peripheral Immune Systems Differently in an Immune Model of Central Nervous System Demyelination. Cells. 2024 Apr 13;13(8):676. doi: 10.3390/cells13080676. PMID: 38667291; PMCID: PMC11048857.

[5] Lamson DR, Tarpley M, Addo K, Ji X, Abu Rabe D, Ehe B, Hughes M, Smith GR, Daye LR, Musso DL, Zheng W, Williams KP. Identification of small molecule antagonists of sonic hedgehog/heparin binding with activity in hedgehog functional assays. Biochim Biophys Acta Gen Subj. 2024 Nov;1868(11):130692. doi: 10.1016/j.bbagen.2024.130692. Epub 2024 Aug 14. PMID: 39151833; PMCID: PMC11486593.

[6] Mao C, Jiang Y, Li Z, Zhou W, Lai Y, Wang C, Lu M, Chen W. Embryonic exposure to Smoothened Agonist disrupts tongue development in mice. Dev Biol. 2025 Aug;524:36-46. doi: 10.1016/j.ydbio.2025.04.018. Epub 2025 Apr 29. PMID: 40311729.