Quantitative evaluation of the biological activity of various brassinosteroids using spiral root induction in rice seeds.

Spiral roots are induced in germinated rice seeds through treatment with nanomolar brassinosteroids (BRs) but not with other plant hormones. Here, we determined the minimum effective concentration (MEC) of various BRs to induce spiral roots in germinated rice seeds. The reciprocal logarithm of MEC, pMEC, was used as the BL-like activity index, which was linearly correlated with the reciprocal logarithm of a 50% effective dose (pED50) as evaluated in the rice lamina inclination assay. Furthermore, a ligand-receptor docking simulation was performed against the BL receptor complex, Arabidopsis thaliana BRI1/SERK1, and the binding free energy (ΔGbind) was calculated for the tested BRs. The ΔGbind calculation was performed using the molecular mechanics/generalized Born surface area method on an ensemble of uncorrelated snapshots collected via molecular dynamics to predict biological activity.

Structure modification of nonsteroidal brassinolide-like compound, NSBR1.

Brassinolide (BL) is a possible plant growth regulator in agriculture, but the presence of a steroid skeleton hampers the field application of BL in agriculture because of its high synthetic cost. We discovered NSBR1 as the first nonsteroidal BL-like compound using in silico technology. Searching for more potent BL-like compounds, we modified the structure of NSBR1 with respect to 2 benzene rings and the piperazine ring. The activity of synthesized compounds was measured in Arabidopsis hypocotyl elongation. The propyl group of butyryl moiety of NSBR1 was changed to various alkyl groups, such as straight, branched, and cyclic alkyl chains. Another substituent, F, at the ortho position of the B ring toward the piperazine ring was changed to other substituents. A methyl group was introduced to the piperazine ring. Most of the newly synthesized compounds with the 3,4-(OH)2 group at the A ring significantly elongated the hypocotyl of Arabidopsis.

Duloxetine ameliorates the impairment of diffuse noxious inhibitory control in rat models of peripheral neuropathic pain and knee osteoarthritis pain.

Diffuse noxious inhibitory control (DNIC) is a phenomenon to reflect descending pain modulation in animals. Conditioned pain modulation (CPM) is the human counterpart of DNIC and is reduced in patients with several chronic pain conditions. Duloxetine is a serotonin and noradrenaline reuptake inhibitor that ameliorates CPM impairment in patients with diabetic neuropathy. Although some studies have reported the effects of different pharmacological agents on CPM, few studies have compared the effects of some analgesics in both humans and rodents. Therefore, we established a stable evaluation method for DNIC in rats and determined whether duloxetine and other specific analgesics affect DNIC impairment in rat models of peripheral neuropathic pain and osteoarthritis pain, two types of chronic pain. As a conditioning stimulus, capsaicin was injected into the forepaw of rats. The paw withdrawal threshold (PWT) in response to mechanical pressure was measured for the hindpaw. Peripheral neuropathic pain and osteoarthritis pain models were developed by partial sciatic nerve ligation (PSNL) and the intra-articular injection of 2 mg monoiodoacetate (MIA), respectively. Capsaicin (30-100 µg/site) increased the PWT, in a dose-dependent manner, in naive rats. The threshold significantly increased at 30 µg and reached its maximal level at 100 µg. The change in PWT following capsaicin injection was significantly reduced in PSNL-treated rats, but the threshold was increased by the subcutaneous administration of duloxetine (10 mg/kg). The oral administrations of pregabalin (10 mg/kg) and celecoxib (3 mg/kg) did not affect the PWT in PSNL-treated rats. Similarly, MIA-injected rats also showed a reduced change in PWT following capsaicin injection. Duloxetine, but not pregabalin and celecoxib, significantly increased the PWT in MIA-injected rats. These results suggested that duloxetine can directly ameliorate DNIC impairment in rat models of chronic pain. Duloxetine may be useful for modulating chronic pain by restoring function to the endogenous, descending, inhibitory pathway.