Identification of morin as an agonist of imidazoline I-3 receptor for insulin secretion in diabetic rats.

Morin is a flavonoid contained in guava that is known to reduce hyperglycemia in diabetics. Morin has been demonstrated to increase plasma insulin. However, the mechanism(s) remains unknown. The present study is designed to investigate the effect of morin on the imidazoline receptor (I-R) that regulates insulin secretion. We used Chinese hamster ovary (CHO) cells transfected with an I-R expression construct (NISCH-CHO-K1 cells) to identify the direct effect of morin on the I-R. Moreover, the imidazoline I3 receptor (I-3R) is known to be present in pancreatic ß cells and involved in insulin secretion. Therefore, we applied a specific antagonist (KU14R) to block I-3R in diabetic rats. Additionally, the effect of morin on insulin secretion was characterized in isolated pancreatic islets. Morin decreased blood glucose levels by increasing plasma insulin levels in diabetic rats. In CHO cells expressing an I-R, morin increased calcium influx in a dose-dependent manner. Additionally, KU14R dose-dependently inhibited the morin-induced effects, including hypoglycemia and the increase in insulin secretion and plasma C-peptide levels, in diabetic rats. Furthermore, morin enhanced insulin secretion from isolated pancreatic islets, and this effect was also dose-dependently inhibited by KU14R. Phospholipase C (PLC) is known to couple with the I-R, and a PLC inhibitor dose-dependently attenuated the insulin secretion induced by morin in isolated pancreatic islets. Taken together, these data suggest that morin can activate I-3R to enhance insulin secretion. Therefore, it would be useful to develop morin into a treatment for diabetic disorders.

Upregulation of IRAS/nischarin (I1-imidazoline receptor), a regulatory protein of µ-opioid receptor trafficking, in postmortem prefrontal cortex of long-term opiate and mixed opiate/cocaine abusers.

Imidazoline receptor antisera-selected (IRAS)/nischarin, a putative I1-imidazoline receptor, has recently been shown to regulate µ-opioid receptor (OR) trafficking and resensitisation. To study a possible involvement of this µ-OR regulator in opiate dependence, the present study assessed by Western blot analysis the contents of IRAS/nischarin and µ-OR in total homogenates and subcellular preparations of postmortem human prefrontal cortex (PFC/BA9) of long-term opiate and mixed opiate/cocaine abusers as well as of matched healthy control subjects. In the PFC/BA9 of long-term opiate/cocaine abusers (all subjects together) IRAS/nischarin content was increased (+67%, p < 0.01, n = 11) when compared with matched controls (n = 10). Similar increases were found for the subgroups of opiate (+72%, n = 6) and mixed opiate/cocaine (+61%, n = 5) abusers. IRAS/nischarin immunocontents were also found increased in subcellular membrane preparations (+61%, p < 0.05, n = 10) of PFC/BA9 from opiate addicts. In the same brain samples, the levels of µ-OR were not different to those in control subjects. Based on the increased contents in brains of opiate abusers and the reported function as µ-OR regulator, IRAS/nischarin could represent a new promising target for treatment of opiate use disorder.

Effects of I2-imidazoline receptor (IR) alkylating BU99006 in the mouse brain: Upregulation of nischarin/I1-IR and µ-opioid receptor proteins and modulation of associated signalling pathways.

5-isothiocyanato-2-benzofuranyl-2-imidazoline (BU99006) was shown to selectively and irreversibly bind to I2-imidazoline receptors (IRs) in vitro and in vivo, but cell signalling consequences of I2-IR alkylation have not been reported previously. This study assessed by Western blot the effects of BU99006 on nischarin (candidate I1-IR), µ-OR (regulated by nischarin) and associated signalling mediators in the mouse brain. Acute treatment with BU99006 (20 mg/kg, i.p., 1-3 h) led to fast (peak at 1 h) and shortlasting (decline up to 3 h) upregulation of nischarin and µ-OR contents in the hippocampus (less or non-significant effects in cortex) and altered the expression of cytoskeletal ß-actin (reduced contents at 3 h). In the same hippocampal samples of BU99006-treated mice, an inhibition of the MAPK species MEK, ERK and JNK was detected at 1 and/or 2 h after drug administration, which was paralleled by enhanced calpain activity (increased contents of p25 and spectrin breakdown products). Correlation analysis indicated the involvement of cdk5/p25 in MEK/ERK inhibition. These neurochemical effects of I2-alkylating BU99006 show a close relation between I1- and I2-IRs expressed in the mouse brain and between these receptors and the µ-OR, accompanied by cytoskeletal alterations and differential effects on multifunctional MAPK and cdk5 signalling pathways.

Expression of integrin-binding protein Nischarin in metastatic breast cancer.

The present study aimed to investigate the expression of Nischarin protein in primary breast cancer (PBC), and to evaluate its role in tumor metastasis. Paired specimens of breast cancer tissues and adjacent normal tissues were surgically obtained from 60 patients with PBC at the Zhejiang Cancer Hospital (Hangzhou, China). Nischarin protein concentrations were determined by an ELISA assay. Breast cancer tissues exhibited a significantly lower concentration of Nischarin (5.86 ± 3.19 ng/ml) compared with that of the adjacent noncancerous tissues (9.25 ± 3.65 ng/ml; P<0.001). Furthermore, cancer tissue from patients with lymph node metastasis had significantly lower levels of Nischarin protein (4.69 ± 2.40 ng/ml) than those of patients without lymph node metastasis (7.04 ± 3.47 ng/ml; P=0.004). There was no significant difference in Nischarin protein expression levels between patients with grade I, II or III PBC (grade I, 5.44 ± 3.57 ng/ml; grade II, 6.42 ± 3.85 ng/ml and grade III, 5.10 ± 1.18 ng/ml; P=0.765). The significant differences in the expression of Nischarin between: i) Cancer tissue and noncancerous tissue and ii) patients with and without lymph node metastasis, suggested that Nischarin may have a significant role in tumor occurrence and metastasis of breast cancer. Nischarin expression may therefore be used as a marker to predict the invasiveness and metastasis of PBC.