Activation of nucleotide-binding oligomerization domain-containing protein 1 by diaminopimelic acid contributes to cerebral ischemia-induced cognitive impairment.

Cerebral ischemia-reperfusion (I/R)-induced brain tissue injury is a major obstacle for acute stroke management. Nucleotide-binding oligomerization domain-containing protein 1 (NOD1) is reported to play a critical role in the regulation of myocardial or hepatic I/R injury. However, its role in cerebral I/R remains elusive. The mouse model of middle cerebral artery occlusion (MCAO) was applied in the study. The cerebral I/R mice were received either PBS or diaminopimelic acid (DAP)-pretreatment. All sham, MCAO, and MCAO + DAP mice were subject to the neurological behavior tests. The proinflammatory cytokines and autophagy-related proteins were determined by ELISA, RT-qPCR, and Western blot analysis, respectively. We found that NOD1 was substantially upregulated in the hippocampus of MCAO mice. DAP treatment significantly enhanced proinflammatory cytokine production and autophagy-related protein expression, leading to enlarged cerebral infarction size and poor neurological performance in MCAO + DAP mice compared to MCAO mice. We concluded that activation of NOD1 promotes cerebral I/R injury suggesting that NOD1 may serve as a promising target for alleviating the adverse effects of cerebral I/R.

Nod1 activation by bacterial iE-DAP induces maternal-fetal inflammation and preterm labor.

There is a strong association between infection and prematurity; however, the underlying mechanisms remain largely unknown. Nod1 and Nod2 are intracellular pattern recognition receptors that are activated by bacterial peptides and mediate innate immunity. We previously demonstrated that human first-trimester trophoblasts express Nod1 and Nod2, which trigger inflammation upon stimulation. This study sought to determine the expression and function of Nod1 and Nod2 in third-trimester trophoblasts, and to characterize the in vivo effects of Nod1 activation on pregnancy outcome. Human term placental tissues and isolated term trophoblast expressed Nod1, but not Nod2. Activation of Nod1 by its agonist, bacterial γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP), in term trophoblast cultures induced a proinflammatory cytokine profile, characterized by elevated levels of secreted IL-6, GRO-α, and MCP-1, when compared with the control. However, these cytokines were not upregulated in response to Nod2 stimulation with bacterial MDP. Administration of high-dose bacterial iE-DAP to pregnant C57BL/6J mice on embryonic day 14.5 triggered preterm delivery within 24 h. iE-DAP at a lower dose that did not induce prematurity, reduced fetal weight, altered the cytokine profile at the maternal-fetal interface, and induced fetal inflammation. Thus, functional Nod1 is expressed by trophoblast cells across gestation and may have a role in mediating infection-associated inflammation and prematurity. This study demonstrates that pattern recognition receptors, other than the TLRs, may be implicated or involved in infection-associated preterm labor.

NOD1 expression in the eye and functional contribution to IL-1beta-dependent ocular inflammation in mice.

PURPOSE: NOD1 plays an important role in host defense and recognizes the minimal component of bacterial cell walls, meso-diaminopimelic acid (iE-DAP). Polymorphisms in NOD1 are associated with autoinflammatory diseases characterized by uveitis such as Crohn's disease and sarcoidosis. NOD1 is homologous to NOD2, which is responsible for an autosomal dominant form of uveitis. Nonetheless, the role of NOD1 in intraocular inflammation has not been explored. The induction of uveitis by iE-DAP in mice and the potential contribution of interleukin (IL)-1beta were investigated. METHODS: BALB/c mice or mice deficient in caspase-1 or IL-1R1 and their congenic controls were injected intravitreally with iE-DAP or saline. The time course, dose response, and contribution of IL-1beta to ocular inflammation were quantified by intravital video microscopy, histology, and immunohistochemistry. NOD1 and IL-1beta were measured in eye tissue by immunoblotting and ELISA. RESULTS: NOD1 protein is expressed in the eye and promotes ocular inflammation in a dose- and time-dependent fashion. The authors previously defined the role of IL-1beta in NOD2 uveitis and tested whether NOD1 and NOD2 used similar mechanisms. Treatment with iE-DAP significantly increased IL-1beta, which was caspase-1 dependent. However, in contrast to NOD2, caspase-1 and IL-1R1 were essential mediators of iE-DAP-induced uveitis, suggesting that NOD1 and NOD2 induce ocular inflammation by distinct mechanisms involving IL-1beta. CONCLUSIONS: These findings demonstrate that NOD1 is expressed within the eye and that its activation results in uveitis in an IL-1beta-dependent mechanism. Characterizing the differences between NOD1 and NOD2 responses may provide insight into the pathogenesis of uveitis.

Antitumor effects of novel immunoactive peptides, FK-156 and its synthetic derivatives.

Effects produced by intratumor or systemic application of FK-156 and its synthetic derivatives on the syngeneic P388-DBA/2 mouse system were investigated. Among 21 compounds tested, FK-156, FK-565, FR-46758, FR-48217, FR-46091 and FR-47920 substantially suppressed tumor growth when directly injected into a tumor mass and further experiments showed that FK-156, FK-565 and FR-46758 were effective even when administered subcutaneously into site remote from tumor. The mechanisms of growth inhibition are strongly suggested to be host mediated, because these three compounds have remarkably low cytotoxicity against P388 cells in vitro. A single dose of FK-565, however, markedly decreased body weight in healthy DBA/2 mice, whereas FK-156 and FR-46758 did not. These results indicate the superiority of FK-156 and FR-46758 as immunotherapeutic agents over FK-565 with respect to their safety for treatment of cancer. Although significant life-span prolongation could not be seen in the two-injection regimen of six compounds in either system, systemic multiple injections of FK-156 and FR-46758 provided a statistically significant increase in the median survival time of P388 tumor bearing mice.