Inducible expression of endomorphins in murine dendritic cells

Bone marrow precursor cells were extracted from C57BL/6J mice aged 7-8 weeks, and dendritic cells were purified using anti-CD1 lc （a specific marker for dendritic cells） antibody-coated magnetic beads. Immunofluorescence staining revealed that the expression levels of endomorphin-1 and endomorphin-2 were upregulated in dendritic cells activated by lipopolysaccharide. An enzyme Jmmunoassay showed that lipopolysaccharide and other Toll-like receptor ligands promoted the secretion of endomorphin-1 and endomorphin-2 from activated dendritic cells. [3H]-thymidine incorporation demonstrated that endomorphin-1 and endomorphin-2 both inhibited the proliferation of T lymphocyte induced by activated dendritic cells. Furthermore, this immunosuppressive effect was blocked by CTOP, a specific antagonist of IJ-opioid receptors. Our experimental findings indicate that activated dendritic cells can induce the expression and secretion of endomorphins, and that endomorphins suppress T lymphocyte proliferation through activation of iJ-opioid receptors.

Structure-activity relationship of endomorphins and their analogs

To study the structure-activity relationship of endomorphins (EMs), the action of opioid receptor binding (AORB), analgesic activity and vasodilator effects of EMs and their eight analogs were investigated, which were prepared by rationally replacing the 2-/3-amino acid (Aa) of EMs. The results showed: (i) The 2-Aa was comparatively more related to the selectivity of EMs while the 3-Aa to their affinity; (ii) the analgesia and vasodilatation of EMs and their analogs were not completely dictated by their AORB (in vitro), the action of [D-Pro2]EM-2 was unusual; (iii) EMs lost their analgesia in the central nervous system and their vasodilatation in the circulatory system with different mechanisms; the former was due to the degradation of some peptidase, and the latter possibly due to the feedback inhibition.

Effects of moxibustion on dynorphin and endomorphin in rats with chronic visceral hyperalgesia

AIM:To observe the analgesic effects of moxibustion in rats with chronic visceral hyperalgesia and its influence on the concentration of dynorphin(Dyn) and endomorphin(EM) in spinal cord.METHODS:The rat model of chronic visceral hyperalgesia was established by colorectal distention(CRD).In moxibustion(MX) group,moxibustion was applied once daily for 7 d;in sham moxibustion(SM) group,moxibustion was given to the same acupoints but with the nonsmoldered end of the moxa stick.Model control(MC) group and normal control group were also studied.The scoring system of abdominal withdrawal reflex was used to evaluate visceral pain for behavioral assessment.Enzyme linked immunosorbent assay was performed to determine the concentrations of Dyn and EM in spinal cord.RESULTS:Moxibustion significantly decreased visceral pain to CRD in this rat model,and no significant difference was detected between the SM group and the MC group.In MX group,moxibustion also increased the concentrations of Dyn and EM in spinal cord,and no significant difference was found between the SM group and the MC group.CONCLUSION:Moxibustion therapy can significantly enhance the pain threshold of rats with chronic visceral hyperalgesia,and the effect may be closely related to the increased concentration of Dyn and EM in spinal cord.

Endomorphin analogues with balanced affinity for bothμ- andδ-opioid receptors

Analogues of endomorphin and tripeptidcs modified at positions 4 and 3,respectively,with various phenylalanine analogues were synthesized and their affinities for opioid receptors were evaluated.Most of the peptides exhibited potentμ-receptor affinity and selectivity,among them,compound 7（Dmt-Pro-Tmp-Tmp-NH_2） exhibited potent affinity for bothμ-andδ-receptors （K_iμ= 0.47 nmol/L,K_iδ= 1.63 nmol/L）.