Tat-indoleamine 2,3-dioxygenase 1 elicits neuroprotective effects on ischemic injury

Indoleamine 2, 3-dioxygenase 1 activation in macrophage exacerbates hepatic ischemia-reperfusion injury by triggering hepatocyte ferroptosis

BACKGROUND

Hepatic Ischemia-reperfusion (I/R) injury, critical challenge in liver surgery and transplantation, exerts a significant impact on the prognosis and survival of patients. Inflammation and cell death play pivotal roles in pathogenesis of hepatic I/R injury. Indoleamine 2, 3-dioxygenase 1 (IDO-1), a key enzyme involved in the kynurenine pathway, has been extensively investigated for its regulatory effects on innate immune responses and cell ferroptosis. However, the precise involvement of IDO-1 in hepatic I/R injury remains unclear.

METHODS

IDO-1 knockout mice were generated to establish a murine model of liver partial warm ischemia and reperfusion, while an in vitro Hypoxia/Reoxygenation (H/R) model was employed to simulate ischemia/reperfusion injury.

RESULTS

The involvement of ferroptosis was observed to be involved in hepatic I/R injury, and effective mitigation of liver injury was achieved through the inhibition of ferroptosis. In the context of hepatic I/R injury, up-regulation of IDO-1 was found in macrophages exhibiting prominent M1 polarization and impaired efferocytosis. Deficiency or inhibition of IDO-1 alleviated hepatocytes ferroptosis and M1 polarization induced by hepatic I/R injury, while also enhancing M2 polarization and promoting efferocytosis in macrophages. Furthermore, depletion of macrophages attenuated ferroptosis in hepatocytes induced by hepatic I/R injury.

CONCLUSION

This study highlights the crucial role of IDO-1 activation in macrophages in triggering ferroptosis in hepatocytes during hepatic ischemia-reperfusion injury. Our findings suggest that targeting IDO-1 could be a promising therapeutic strategy for mitigating hepatic I/R injury associated with liver surgery and transplantation.

Tat-RAN attenuates brain ischemic injury in hippocampal HT-22 cells and ischemia animal model

Oxidative stress plays a key role in the pathogenesis of neuronal injury, including ischemia. Ras-related nuclear protein (RAN), a member of the Ras superfamily, involves in a variety of biological roles, such as cell division, proliferation, and signal transduction. Although RAN reveals antioxidant effect, its precise neuroprotective mechanisms are still unclear. Therefore, we investigated the effects of RAN on HT-22 cell which were exposed to H₂O₂-induced oxidative stress and ischemia animal model by using the cell permeable Tat-RAN fusion protein. We showed that Tat-RAN transduced into HT-22 cells, and markedly inhibited cell death, DNA fragmentation, and reactive oxygen species (ROS) generation under oxidative stress. This fusion protein also controlled cellular signaling pathways, including mitogen-activated protein kinases (MAPKs), NF-κB, and apoptosis (Caspase-3, p53, Bax and Bcl-2). In the cerebral forebrain ischemia animal model, Tat-RAN significantly inhibited both neuronal cell death, and astrocyte and microglia activation. These results indicate that RAN significantly protects against hippocampal neuronal cell death, suggesting Tat-RAN will help to develop the therapies for neuronal brain diseases including ischemic injury.

Can kynurenine pathway be considered as a next-generation therapeutic target for Parkinson's disease? An update information

By far, no revolutionary breakthrough in the treatment of Parkinson's disease (PD) was found. It is indeed a knotty problem to select a satisfactory strategy for treating some patients with advanced stage PD. Development of novel therapeutic targets against PD has been an urgent task faced by global PD researchers. Targets in the tryptophan-kynurenine pathway (KP) were then considered. Metabolites in the KP are liposoluble. Some neurotoxic metabolites, including 3-hydroxykynurenine and its downstream 3-hydroxyanthranilic acid and quinolinic acid, are mainly produced peripherally. They can easily cross the blood-brain barrier (BBB) and exert their neurotoxic effects in the central neuron system (CNS), which is considered as a potential pathophysiological mechanism of neurodegenerative diseases. Hence, agents against the targets in the KP have two characteristics: (1) being independent from the dopaminergic system and (2) being seldom affected by the BBB. Inspiringly, one agent, namely, the inhibitor of indoleamine 2,3-dioxygenase 1, has been currently reported to present satisfactory efficacy comparable to levodopa, implying that the KP might be a potential novel target for PD. This review collected and summarized the updated information regarding the association of the KP with PD, which is helpful for understanding the clinical value of the KP in the PD scenario.

NLRP3 Inflammasome Activation: A Therapeutic Target for Cerebral Ischemia–Reperfusion Injury

Millions of patients are suffering from ischemic stroke, it is urgent to figure out the pathogenesis of cerebral ischemia–reperfusion (I/R) injury in order to find an effective cure. After I/R injury, pro-inflammatory cytokines especially interleukin-1β (IL-1β) upregulates in ischemic brain cells, such as microglia and neuron. To ameliorate the inflammation after cerebral I/R injury, nucleotide-binding oligomerization domain (NOD), leucine-rich repeat (LRR), and pyrin domain-containing protein 3 (NLRP3) inflammasome is well-investigated. NLRP3 inflammasomes are complicated protein complexes that are activated by endogenous and exogenous danger signals to participate in the inflammatory response. The assembly and activation of the NLRP3 inflammasome lead to the caspase-1-dependent release of pro-inflammatory cytokines, such as interleukin (IL)-1β and IL-18. Furthermore, pyroptosis is a pro-inflammatory cell death that occurs in a dependent manner on NLRP3 inflammasomes after cerebral I/R injury. In this review, we summarized the assembly and activation of NLRP3 inflammasome; moreover, we also concluded the pivotal role of NLRP3 inflammasome and inhibitors, targeting the NLRP3 inflammasome in cerebral I/R injury.

Indoleamine-2,3-dioxygenase-related anti-inflammatory effects of 3-aminobenzamide and infliximab in experimental colitis

OBJECTIVE

This study aimed to investigate the presence of indoleamine-2,3-dioxygenase and bacterial translocation after the administration of 3-aminobenzamide and infliximab in the TNBS model of rat colitis.

METHODS

The study group was divided into five categories as follows: group 1: (control), group 2: colitis+saline, group 3: colitis+3-aminobenzamide, group 4: colitis+infliximab, and group 5: colitis+3-aminobenzamide+infliximab. Intestinal mesenteric cultures were incubated on specific agar media plates under aerobic and anaerobic conditions, bacterial translocation was evaluated and assessed as colony-forming units per gram of tissue. Colonic tissue samples were evaluated by Western blotting method to detect the presence of indoleamine-2,3-dioxygenase.

RESULTS

The results obtained were as follows: group 1: normal gut flora; group 2: eight of nine samples had bacterial translocation, of which six of them had positive indoleamine-2,3-dioxygenase protein; group 3: five of nine samples had bacterial translocation, of which seven of them had positive indoleamine-2,3-dioxygenase; group 4: three of nine samples had bacterial translocation, of which seven of them had positive indoleamine-2,3-dioxygenase; and group 5: only one sample had exact indoleamine-2,3-dioxygenase protein.

CONCLUSION

Altered expression of indoleamine-2,3-dioxygenase results in a lower bacterial translocation via infliximab compared with 3-aminobenzamide treatment. Combined treatments emphasized different approaches for the new molecules related to indoleamine-2,3-dioxygenase.