Decreased PD-1/PD-L1 Expression Is Associated with the Reduction in Mucosal Immunoglobulin A in Mice with Intestinal Ischemia Reperfusion

Drug therapy for myocarditis induced by immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs), including cytotoxic T-lymphocyte antigen 4 (CTLA-4), programmed cell death 1 (PD-1), and its ligand 1 (PD-L1), have improved the survival in multiple types of cancers; however, ICIs may cause cardiovascular toxicity. Although rare, ICI-mediated cardiotoxicity is an extremely serious complication with a relatively high mortality. In this review, we discuss the underlying mechanism and clinical manifestations of cardiovascular toxicity induced by ICIs. According to previous studies, multiple signaling pathways are involved in myocarditis induced by ICIs. Further, we summarize the clinical trials of drugs for the treatment of ICI-associated myocarditis. Although these drugs have shown the beneficial effects of alleviating cardiac function and reducing mortality rates, their efficacy is not optimal. Finally, we discuss the therapeutic potential of some novel compounds as well as the underlying mechanisms of their action.

The efficacy of bone marrow mesenchymal stem cells on rat intestinal immune-function injured by ischemia/reperfusion

Background

Transplantation of bone marrow mesenchymal stem cells (BMSCs) has a promising therapeutic efficiency for varieties of disorders caused by ischemia or reperfusion impairment. It has been shown that BMSCs can mitigate intestinal ischemia/reperfusion (I/R) injuries, but the underlying mechanism is still unclear. This study aimed at investigating the efficacy of BMSCs on the immune function of intestinal mucosal microenvironment after I/R injuries.

Methods

Twenty adult Sprague-Dawley rats were randomly assigned to a treatment or a control group. All the rats underwent superior mesenteric artery clamping and unclamping. In the treatment group, BMSCs were implanted into the intestine of ten rats by direct submucosal injection whereas the other ten rats in the control group were injected with the same volume of saline. On the fourth and seventh day after BMSCs transplantation, intestinal samples were examined for the CD4 (CD4-positive T-lymphocytes)/CD8 (CD8-positive T-lymphocytes) ratio of the bowel mucosa via flow cytometry, and for the level of Interleukin-2 (IL-2), Interleukin-4 (IL-4) and Interleukin-6 (IL-6) via ELISA. Paneth cell counts and Secretory Immunoglobulin A (SIgA) level were examined via immunohistochemical (IHC) analysis. Real time PCR (RT-PCR) was used to detect the expression levels of tumor necrosis factor-α (TNF-α) and trypsinogen (Serine 2) (PRSS2) genes. White blood cell (WBC) count was measured by manual counting under the microscope.

Results

The CD4/CD8 ratio in the treatment group was significantly lower compared with that in the control group. The concentration of IL-2 and IL-6 was lower in the treatment group compared with the control group, while the level of IL-4 is the reverse between the two groups. The number of Paneth cells in intestinal mucosa increased significantly, while the level of SIgA in intestinal mucosa decreased significantly, after BMSCs transplantation. The gene expression levels of TNF-α and PRSS2 in intestinal mucosa of treatment group were significantly lower than those of control group. The WBC count in the treatment group was significantly lower than that in the control group.

Conclusion

We identified immune-relevant molecular changes that may explain the mechanism of BMSCs transplantation efficacy in alleviating rat intestinal immune-barrier after I/R.

Inhibition of PD-1 Alters the SHP1/2-PI3K/Akt Axis to Decrease M1 Polarization of Alveolar Macrophages in Lung Ischemia-Reperfusion Injury

Polarization of alveolar macrophages (AMs) into the M1 phenotype contributes to inflammatory responses and tissue damage that occur during lung ischemia-reperfusion injury (LIRI). Programmed cell death factor-1 (PD-1) regulates polarization of macrophages, but its role in LIRI is unknown. We examined the role of PD-1 in AM polarization in models of LIRI in vivo and in vitro. Adult Sprague-Dawley rats were subjected to ischemia-reperfusion with or without pretreatment with a PD-1 inhibitor, SHP1/2 inhibitor, or Akt activator. Lung tissue damage and infiltration by M1-type AMs were assessed. As an in vitro complement to the animal studies, rat alveolar macrophages in culture were subjected to oxygen/glucose deprivation and reoxygenation. Levels of SHP1/2 and Akt proteins were evaluated using Western blots, while levels of pro-inflammatory cytokines were measured using enzyme-linked immunosorbent assays. Injury upregulated PD-1 both in vivo and in vitro. Inhibiting PD-1 reduced the number of M1-type AMs, expression of SHP1 and SHP2, and levels of inflammatory cytokines. At the same time, it partially restored Akt activation. Similar results were observed after inhibition of SHP1/2 or activation of the PI3K/Akt pathway. PD-1 promotes polarization of AMs to the M1 phenotype and inflammatory responses through the SHP1/2-PI3K/Akt axis. Inhibiting PD-1 may be an effective therapeutic strategy to limit LIRI.

Divergent roles of PD-L1 in immune regulation during ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a type of pathological injury that commonly arises in various diseases. Various forms of immune response are involved in the process of I/R injury. As a member of the B7 costimulatory molecule family, programmed death 1-ligand 1 (PD-L1) is an important target for immune regulation. Therefore, PD-L1 may be implicated in the regulation of I/R injury. This review briefly describes the immune response during I/R injury and how PD-L1 is involved in its regulation by focusing on findings from various I/R models. Despite the limited number of studies in this field of research, PD-L1 has shown sufficient potential as a clinical therapeutic target.

Association Between Activation of the Programmed Cell Death-1 (PD-1)/Programmed Death-Ligand 1 (PD-L1) Pathway and Pain in Patients with Cancer

Background

The aim of this study was to investigate the clinical correlation between sPD-1 (soluble programmed cell death-1) and PD-1 (programmed cell death-1) expression and cancer pain.

Material/Methods

sPD-1 content in peripheral blood was determined by enzyme-linked immunosorbent assay (ELISA). T cell surface-positive rate was determined by flow cytometry, and the correlation of clinical characteristics of patients with cancer pain was analyzed.

Results

The positive expression rate of PD-1 in sPD-1 and T cells of patients with cancer pain was higher than that in normal patients. There was a significant correlation between sPD-1 and PD-1 positivity on T cell surface with tumor type, differentiation degree, and VAS scores of patients with cancer pain (P<0.05). Peripheral blood sPD-1 level and PD-1 positivity in patients with liver cancer and melanoma cancer were higher than those in patients with renal cell carcinoma and breast cancer. In addition, peripheral blood sPD-1 level and PD-1 positivity in patients with poorly-differentiated cancer pain were higher than those in patients with intermediately- to well-differentiated cancer. The sPD-1 content was lower and PD-1 positivity rate was higher in cancer pain patients with low VAS scores.

Conclusions

The positive expression rate of sPD-1 and PD-1 in patients with cancer pain is higher than that in normal people. The activation rate of the PD-1/PD-L1 pathway was mediated by sPD-1 and PD-1 positive expression, age, tumor type, and differentiation. There are correlations between clinical characteristics such as degree and pain level as shown by VAS score.

Activation of PD-1 Protects Intestinal Immune Defense Through IL-10/miR-155 Pathway After Intestinal Ischemia Reperfusion

BACKGROUND

To date, mechanisms of intestinal immunoglobulin (Ig) dysfunction following intestinal ischemia/reperfusion (I/R) remain unclear. Programmed death 1 (PD-1) is associated with immune responses of lymphocytes.

AIM

We aimed to verify the hypothesis that activation of PD-1 may improve intestinal immune dysfunction by regulating IL-10/miR-155 production after intestinal IR injury.

METHODS

Intestinal I/R injury was induced in mice by clamping the superior mesenteric artery for 1 h followed by 2-h reperfusion. PD-L1 fusion Ig, anti-interleukin (IL)-10 monoclonal antibody (mAb), and microRNA (miR)-155 agomir were administered. PD-1 expression, IL-10 mRNA, and protein expression in Peyer's patches (PP) CD4⁺ cells were measured. MiR-155 levels, tumor necrosis factor (TNF)-α and IL-1β concentration, and activation-induced cytidine deaminase (AID), a key enzyme for intestinal immune antibodies, in PP tissues were measured, respectively. Importantly, the production and cecal bacteria-binding capacity of IgA and IgM were detected.

RESULTS

Intestinal I/R led to decreased PD-1 expression, imbalanced production, and impaired bacteria-binding capacity of IgA and IgM. Activating PD-1 by PD-L1 Ig facilitated IL-10 synthesis, then decreased miR-155 levels, and subsequently promoted AID expression and reduced TNF-α, IL-1β concentration. Upregulation of AID improved the disruptions of intestinal immune barrier caused by IgA and IgM dysfunction. Anti-IL-10 mAb and miR-155 agomir abolished the protective effects of PD-L1 Ig on the intestinal immune defense.

CONCLUSION

Activation of PD-1 with PD-L1 Ig relieves intestinal immune defensive injury through IL-10/miR-155 pathway following intestinal I/R attack. PD-1, IL-10, and miR-155 may be potential targets for the damages of intestinal barrier and immunity.

Pretreatment with the ALDH2 agonist Alda-1 reduces intestinal injury induced by ischaemia and reperfusion in mice

Many studies demonstrate that activation of aldehyde dehydrogenase 2 (ALDH2) protects against oxidative stress via detoxification of cytotoxic aldehydes, and could attenuate cardiac, cerebral, lung and renal ischaemia-reperfusion (I/R) injuries. However, the effect of ALDH2 in intestinal I/R is unknown. The present study was set up to determine whether an ALDH2 agonist, Alda-1, could alleviate intestinal injury after gut I/R. In a mouse model of intestinal I/R injury, histological grading, proinflammatory cytokines, oxidative stress, cellular apoptosis, chemokine contents, ALDH2 activity, 4-hydroxy-trans-2-nonenal (4-HNE) and malondialdehyde (MDA) were evaluated. The results indicated that I/R treatment conferred elevation in pathological scores, proinflammatory cytokines, oxidative stress, cellular apoptosis and chemokine levels, accompanied by accumulated 4-HNE and MDA. No significant changes in ALDH2 activity were observed after I/R. However, Alda-1 pretreatment significantly decreased these injurious indicators, concomitant with up-regulated ALDH2 activity, and lessened 4-HNE and MDA accumulation. Taken together, our results implicate activation of ALDH2 by Alda-1 in the significant abatement intestinal I/R injury.

TGF-β1 improves mucosal IgA dysfunction and dysbiosis following intestinal ischaemia-reperfusion in mice

Intestinal ischaemia/reperfusion (I/R) severely disrupts gut barriers and leads to high mortality in the critical care setting. Transforming growth factor (TGF)-β1 plays a pivotal role in intestinal cellular and immune regulation. However, the effects of TGF-β1 on intestinal I/R injury remain unclear. Thus, we aimed to investigate the effects of TGF-β1 on gut barriers after intestinal I/R and the molecular mechanisms. Intestinal I/R model was produced in mice by clamping the superior mesenteric artery for 1 hr followed by reperfusion. Recombinant TGF-β1 was intravenously infused at 15 min. before ischaemia. The results showed that within 2 hrs after reperfusion, intestinal I/R disturbed intestinal immunoglobulin A class switch recombination (IgA CSR), the key process of mucosal IgA synthesis, and resulted in IgA dysfunction, as evidenced by decreased production and bacteria-binding capacity of IgA. Meanwhile, the disruptions of intestinal microflora and mucosal structure were exhibited. Transforming growth factor-β1 activated IgA CSR as evidenced by the increased activation molecules and IgA precursors. Strikingly, TGF-β1 improved intestinal mucosal IgA dysfunction, dysbiosis and epithelial damage at the early stage after reperfusion. In addition, SB-431542, a specific inhibitor of activating mothers against decapentaplegic homologue (SMAD) 2/3, totally blocked the inductive effect of TGF-β1 on IgA CSR and almost abrogated the above protective effects on intestinal barriers. Taken together, our study demonstrates that TGF-β1 protects intestinal mucosal IgA immunity, microbiota and epithelial integrity against I/R injury mainly through TGF-β receptor 1/SMAD 2/3 pathway. Induction of IgA CSR may be involved in the protection conferred by TGF-β1.