Cardiac allograft rejection correlates with increased expressions of Toll-like receptors 2 and 4 and allograft inflammatory factor 1

Toll-like receptor 2 deficiency promotes the generation of alloreactive γδT17 cells after cardiac transplantation in mice

Homograft rejection is the main cause of heart transplantation failure. The role of TLR2, a major member of the toll-like receptor (TLR) family, in transplantation rejection is has yet to be elucidated. In this study, we used a mouse model of acute cardiac transplantation rejection to investigate whether the TLR2 signalling pathway can regulate cardiac transplantation rejection by regulating alloreactive IL-17+γδT (γδT17) cells. We found that the expression of TLR2 on the surface of dendritic cells (DCs) and macrophages increased during acute transplantation rejection. In addition, our investigation revealed that γδT17 cells exert a significant influence on acute cardiac transplantation rejection. TLR2 gene knockout resulted in an increase in alloreactive γδT17 cells in the spleen and heart grafts of recipient mice compared with wild-type recipient mice and an increase in the mRNA expression of IL-17, IL-1β, CCR6, and CCL20 in the heart grafts. In an in vitro experiment, a mixed lymphocyte reaction was conducted to assess the impact of TLR2 deficiency on the generation of γδT17 cells, which further substantiated a significant increase compared to that in wild-type controls. Furthermore, the mixed lymphocyte reaction showed that TLR2 regulated the production of γδT17 cells by regulating the ability of DCs to secrete IL-1β. These results suggest that TLR2 signalling is important for regulating the generation of γδT17 cells after cardiac allograft transplantation.

Asarinin inhibits immunological rejection via the Toll-like receptor-myeloid differentiation factor 88 signaling pathway in vitro

Asarinin has been found to prolong allograft survival and inhibit post-transplant immune rejection via the Toll-like receptor (TLR) signaling pathway. However, the underlying mechanism is not completely understood. Therefore, elucidating the possible pathophysiological role of asarinin in the TLR signaling pathway is essential. Here, dendritic cells were isolated from Sprague-Dawley® rats and cultured with splenocytes from Wistar rats treated with asarinin, lipopolysaccharide (LPS), and/or dimethyl sulfoxide. mRNA expression of TLR-2, TLR-4, myeloid differentiation factor 88 (MyD88), and nuclear factor kB (NF-kB) was determined using real-time polymerase chain reaction. Interleukin (IL)-6 and IL-12 levels were examined using an enzyme-linked immunosorbent assay. LPS resulted in an increase in the expression of TLR-2 rather than TLR-4 and MyD88. Furthermore, it inhibited the secretion of IL-6 and IL-12. MyD88 can be silenced after lentiviral transduction, and LPS can activate MyD88, whereas asarinin can inhibit this kind of activation. The effect of LPS and asarinin on TLR-4 could only be achieved when MyD88 was not silenced by lentivirus transduction. Therefore, asarinin might suppress TLR-4-mediated activation via the MyD88-dependent pathway. Overall, asarinin has a pre-application effect in inhibiting graft rejection.

Expression Pattern and Molecular Mechanism of Oxidative Stress-Related Genes in Myocardial Ischemia-Reperfusion Injury

(1) Background: The molecular mechanism of oxidative stress-related genes (OSRGs) in myocardial ischemia-reperfusion injury (MIRI) has not been fully elucidated. (2) Methods: Differential expression analysis, enrichment analysis, and PPI analysis were performed on the MIRI-related datasets GSE160516 and GSE61592 to find key pathways and hub genes. OSRGs were obtained from the Molecular Signatures Database (MSigDB). The expression pattern and time changes of them were studied on the basis of their raw expression data. Corresponding online databases were used to predict miRNAs, transcription factors (TFs), and therapeutic drugs targeting common differentially expressed OSRGs. These identified OSRGs were further verified in the external dataset GSE4105 and H9C2 cell hypoxia-reoxygenation (HR) model. (3) Results: A total of 134 DEGs of MIRI were identified which were enriched in the pathways of "immune response", "inflammatory response", "neutrophil chemotaxis", "phagosome", and "platelet activation". Six hub genes and 12 common differentially expressed OSRGs were identified. A total of 168 miRNAs, 41 TFs, and 21 therapeutic drugs were predicted targeting these OSRGs. Lastly, the expression trends of Aif1, Apoe, Arg1, Col1a1, Gpx7, and Hmox1 were confirmed in the external dataset and HR model. (4) Conclusions: Aif1, Apoe, Arg1, Col1a1, Gpx7, and Hmox1 may be involved in the oxidative stress mechanism of MIRI, and the intervention of these genes may be a potential therapeutic strategy.

Cyclosporine A, in Contrast to Rapamycin, Affects the Ability of Dendritic Cells to Induce Immune Tolerance Mechanisms

Following organ transplantation, it is essential that immune tolerance is induced in the graft recipient to reduce the risk of rejection and avoid complications associated with the long-term use of immunosuppressive drugs. Immature dendritic cells (DCs) are considered to promote transplant tolerance and may minimize the risk of graft rejection. The aim of the study was to evaluate the effects of immunosuppressive agents: rapamycin (Rapa) and cyclosporine A (CsA) on generation of human tolerogenic DCs (tolDCs) and also to evaluate the ability of these cells to induce mechanisms of immune tolerance. tolDCs were generated in the environment of Rapa or CsA. Next, we evaluated the effects of these agents on surface phenotypes (CD11c, MHC II, CD40, CD80, CD83, CD86, CCR7, TLR2, TLR4), cytokine production (IL-4, IL-6, IL-10, IL-12p70, TGF-β), phagocytic capacity and resistant to lipopolysaccharide activation of these DCs. Moreover, we assessed ability of such tolDCs to induce T cell activation and apoptosis, Treg differentiation and production of Th1- and Th2-characteristic cytokine profile. Data obtained in this study demonstrate that rapamycin is effective at generating maturation-resistant tolDCs, however, does not change the ability of these cells to induce mechanisms of immune tolerance. In contrast, CsA affects the ability of these cells to induce mechanisms of immune tolerance, but is not efficient at generating maturation-resistant tolDCs.

TLR2 and TLR4 mRNA expression levels in liver transplant patients with acute rejection

Toll-like receptors (TLRs) have important role in transplant outcomes by activating the innate immune system and production of pro-inflammatory cytokines, leading to graft rejection. We assessed the expression level of TL2 and TLR4 in acute rejection (AR) on the 1st and 7th^-day post-transplantation. TLR2 and TLR4 expressions were evaluated by real-time PCR in both the AR group (n = 50) and non-AR (n = 50), compared with the control group. Also, the correlation of the expression levels of TLRs between both the 1st and 7th day was analyzed. ROC curve analysis was used to determine the cut-off value for TLRs expression. TLR4 mRNA expression was significantly up-regulated in AR patients vs. the controls on the 1st day (p ≤ 0.05) and it was down-regulated in non-AR vs. controls on the 1st day (p ≤ 0.05). Also, TLR4 expression had decreased in both AR and non-AR groups vs. control on the 7th day (p ≤ 0.05). Both TLR2 and TLR4 expression in comparison to non-AR had increased in the AR group on the 7th day (p ≤ 0.05). TLR2 expression positively correlated between 1st and 7th day in AR (r = 0.3, (p ≤ 0.05) and non-AR group (r = 0.2, p ≤ 0.05). ROC curve analysis showed a cut-off value of TLR2 up to 0.98 with sensitivity 71.05 (95%CI = 54.1-84.6) and specificity 63.27 (95%CI = 48.3-76.6) that could distinguish between AR and non-AR group (p ≤ 0.05). The data support that both TLR2 and TLR4 expression have an effective role in AR after liver transplantation and could be used as possible biomarkers for AR to choose better therapeutic strategies based on immunological aspects.

Damage-Associated Molecular Patterns in Myocardial Infarction and Heart Transplantation: The Road to Translational Success

In the setting of myocardial infarction (MI), ischemia reperfusion injury (IRI) occurs due to occlusion (ischemia) and subsequent re-establishment of blood flow (reperfusion) of a coronary artery. A similar phenomenon is observed in heart transplantation (HTx) when, after cold storage, the donor heart is connected to the recipient's circulation. Although reperfusion is essential for the survival of cardiomyocytes, it paradoxically leads to additional myocardial damage in experimental MI and HTx models. Damage (or danger)-associated molecular patterns (DAMPs) are endogenous molecules released after cellular damage or stress such as myocardial IRI. DAMPs activate pattern recognition receptors (PRRs), and set in motion a complex signaling cascade resulting in the release of cytokines and a profound inflammatory reaction. This inflammatory response is thought to function as a double-edged sword. Although it enables removal of cell debris and promotes wound healing, DAMP mediated signalling can also exacerbate the inflammatory state in a disproportional matter, thereby leading to additional tissue damage. Upon MI, this leads to expansion of the infarcted area and deterioration of cardiac function in preclinical models. Eventually this culminates in adverse myocardial remodeling; a process that leads to increased myocardial fibrosis, gradual further loss of cardiomyocytes, left ventricular dilation and heart failure. Upon HTx, DAMPs aggravate ischemic damage, which results in more pronounced reperfusion injury that impacts cardiac function and increases the occurrence of primary graft dysfunction and graft rejection via cytokine release, cardiac edema, enhanced myocardial/endothelial damage and allograft fibrosis. Therapies targeting DAMPs or PRRs have predominantly been investigated in experimental models and are potentially cardioprotective. To date, however, none of these interventions have reached the clinical arena. In this review we summarize the current evidence of involvement of DAMPs and PRRs in the inflammatory response after MI and HTx. Furthermore, we will discuss various current therapeutic approaches targeting this complex interplay and provide possible reasons why clinical translation still fails.

Role of allograft inflammatory factor-1 in pathogenesis of diseases

Allograft inflammatory factor-1 (AIF-1) is a 17 kDa calcium-binding protein produced by monocytes, macrophages, and lymphocytes; its synthesis is induced by INF-γ. The AIF-1 gene is located in the major histocompatibility complex (MHC) class III region on chromosome 6p21.3, surrounded by surface glycoprotein genes and complement cascade protein genes as well as TNF-α, TNF-β, and NF-κB genes. Increased expression of AIF-1 was observed in several diseases, including endometriosis, breast cancer, atherosclerosis, rheumatoid arthritis, and fibrosis. In this review, we summarise the role of AIF-1 in allograft rejection and the pathogenesis of diseases.

[Increased myocardial expression of Toll-like receptors 2 and 9 as a marker of active myocarditis and a possible predictor of therapeutic effectiveness]

AIM

to investigate the myocardial expression of some structural proteins and markers of cellular proliferation and innate immunity for assessing their possible diagnostic and prognostic role in patients with chronic myocarditis.

SUBJECTS AND METHODS

The investigation enrolled 23 patients (16 men; mean age, 52.0±12.4 years (range, 27 to 73) with various forms of noncoronarogenic myocardial injury who underwent right ventricular endomyocardial biopsy (n=4), intraoperative left ventricular biopsy (n=17) or autopsy (n=2). Prior to their morphological examination, the patients were divided into two groups: 1) 10 patients with dilated cardiomyopathy and presumptive myocarditis; 2) 13 patients with valvular heart disease, hypertrophic cardiomyopathy, myxoma, and chronic pulmonary thromboembolism, presumptively without myocarditis. Along with myocardial histological and immunohistochemical (IHC) examinations, the expression of vimentin, desmin, c-kit, Ki-67, and Toll-like receptors (TLR) 2 and 9 was determined. Polymerase chain reaction was used to identify whether herpes viruses of and parvovirus B19 genomes were present in the blood and myocardial samples; indirect ELISA was applied to estimate the blood level of antibodies against various cardiac antigens.

RESULTS

According to the histological findings, active/borderline lymphocytic myocarditis was diagnosed in all the patients (Group 1) and in 6 patients (Group 2) in conjunction with the underlying disease (only in 9 and 7 patients, respectively), viral genome was detected in the myocardium of 15 patients, including in 5 without morphological signs of myocarditis (parvovirus B19 (n=11), herpesvirus 6 (n=4), herpes simplex virus types 1 and 2 (n=1), Epstein-Barr virus (n=2), and cytomegalovirus (n=1)), and in the blood (n=4). A marked correlation was found between TLR2 and TLR9 expressions and the morphological pattern of active myocarditis in the absence of this correlation with the expression level of other studied markers. The expression level of TLR2 in patients with and without borderline myocarditis was 0 [0; 0,75] and in those with active myocarditis was 1.5 [1; 1,5] points; that of TLR9 was 2 [2; 2] and 4 [3; 4] points, respectively (p<0.001). The expression of TLR2 and TLR9 in patients with borderline myocarditis was lower than in those without myocarditis (0 [0; 0] versus 0 [0; 1] and 2 [1,5; 2] versus 2 [2; 3] points), which can reflect cardiomyocyte destruction/depletion at later stages of the disease. There was also a close correlation between the expression level of TLR2 and that of TLR9 (r=0.824; p<0.001) and with Ki-67 levels (r=-0.531 and r=-0.702; p<0.01). There was also a correlation of the expression of the studied markers with viral persistence (desmin), the degree of myocardial dysfunction and cardiosclerosis (c-kit), which calls for further investigations.

CONCLUSION

Determination of the myocardial expression level of TLR2 and TLR9 may serve as an immunohistochemical marker for myocarditis and preservation of its activity, which is especially valuable in patients with borderline forms. The marked expression of these markers for innate immunity may reflect both one of the mechanisms of genetic predisposition to myocarditis and its severe course and their secondary activation in the pathogenesis of the disease and is a potential target of therapy.

Altered Exosomal RNA Profiles in Bronchoalveolar Lavage from Lung Transplants with Acute Rejection

RATIONALE

The mechanism by which acute allograft rejection leads to chronic rejection remains poorly understood despite its common occurrence. Exosomes, membrane vesicles released from cells within the lung allograft, contain a diverse array of biomolecules that closely reflect the biologic state of the cell and tissue from which they are released. Exosome transcriptomes may provide a better understanding of the rejection process. Furthermore, biomarkers originating from this transcriptome could provide timely and sensitive detection of acute cellular rejection (AR), reducing the incidence of severe AR and chronic lung allograft dysfunction and improving outcomes.

OBJECTIVES

To provide an in-depth analysis of the bronchoalveolar lavage fluid exosomal shuttle RNA population after lung transplantation and evaluate for differential expression between acute AR and quiescence.

METHODS

Serial bronchoalveolar lavage specimens were ultracentrifuged to obtain the exosomal pellet for RNA extraction, on which RNA-Seq was performed.

MEASUREMENTS AND MAIN RESULTS

AR demonstrates an intense inflammatory environment, skewed toward both innate and adaptive immune responses. Novel, potential upstream regulators identified offer potential therapeutic targets.

CONCLUSIONS

Our findings validate bronchoalveolar lavage fluid exosomal shuttle RNA as a source for understanding the pathophysiology of AR and for biomarker discovery in lung transplantation.

Altered Exosomal RNA Profiles in Bronchoalveolar Lavage from Lung Transplants with Acute Rejection

RATIONALE

The mechanism by which acute allograft rejection leads to chronic rejection remains poorly understood despite its common occurrence. Exosomes, membrane vesicles released from cells within the lung allograft, contain a diverse array of biomolecules that closely reflect the biologic state of the cell and tissue from which they are released. Exosome transcriptomes may provide a better understanding of the rejection process. Furthermore, biomarkers originating from this transcriptome could provide timely and sensitive detection of acute cellular rejection (AR), reducing the incidence of severe AR and chronic lung allograft dysfunction and improving outcomes.

OBJECTIVES

To provide an in-depth analysis of the bronchoalveolar lavage fluid exosomal shuttle RNA population after lung transplantation and evaluate for differential expression between acute AR and quiescence.

METHODS

Serial bronchoalveolar lavage specimens were ultracentrifuged to obtain the exosomal pellet for RNA extraction, on which RNA-Seq was performed.

MEASUREMENTS AND MAIN RESULTS

AR demonstrates an intense inflammatory environment, skewed toward both innate and adaptive immune responses. Novel, potential upstream regulators identified offer potential therapeutic targets.

CONCLUSIONS

Our findings validate bronchoalveolar lavage fluid exosomal shuttle RNA as a source for understanding the pathophysiology of AR and for biomarker discovery in lung transplantation.

Altered Exosomal RNA Profiles in Bronchoalveolar Lavage from Lung Transplants with Acute Rejection

RATIONALE

The mechanism by which acute allograft rejection leads to chronic rejection remains poorly understood despite its common occurrence. Exosomes, membrane vesicles released from cells within the lung allograft, contain a diverse array of biomolecules that closely reflect the biologic state of the cell and tissue from which they are released. Exosome transcriptomes may provide a better understanding of the rejection process. Furthermore, biomarkers originating from this transcriptome could provide timely and sensitive detection of acute cellular rejection (AR), reducing the incidence of severe AR and chronic lung allograft dysfunction and improving outcomes.

OBJECTIVES

To provide an in-depth analysis of the bronchoalveolar lavage fluid exosomal shuttle RNA population after lung transplantation and evaluate for differential expression between acute AR and quiescence.

METHODS

Serial bronchoalveolar lavage specimens were ultracentrifuged to obtain the exosomal pellet for RNA extraction, on which RNA-Seq was performed.

MEASUREMENTS AND MAIN RESULTS

AR demonstrates an intense inflammatory environment, skewed toward both innate and adaptive immune responses. Novel, potential upstream regulators identified offer potential therapeutic targets.

CONCLUSIONS

Our findings validate bronchoalveolar lavage fluid exosomal shuttle RNA as a source for understanding the pathophysiology of AR and for biomarker discovery in lung transplantation.

Properties of human blood monocytes. II. Monocytes from healthy adults are highly heterogeneous within and among individuals

BACKGROUND

Human blood monocytes are known to include subsets defined by the expression of CD14 and CD16 but otherwise are often assumed to be relatively homogeneous. However, we had observed additional heterogeneity that led us to a more extensive examination of monocytes.

METHODS

Blood samples from 200 healthy adults without known immunological abnormalities were examined by analysis with a hematology analyzer and by flow cytometry (FCM) to determine leukocyte differential counts, to identify subsets and to measure expression of monocyte-associated molecules.

RESULTS

The estimated cell counts of monocytes, neutrophils, total lymphocytes, and T cells all varied to a similar extent, that is, ±30-35%. The fractions of monocyte subsets defined by CD14 and CD16 or by CD163 expression also varied among individuals. FCM examinations showed that all the monocyte-associated molecules that were examined varied in expression in this increasing order-CD244, CD4, CD38, CD91, CD11b, toll-like receptor 2 (TLR2), TIA-1, CD14 (on CD14(Br+) cells), CD86, CD80, HLA-DQ, CD33, and HLA-DR.

CONCLUSIONS

Human blood monocytes are heterogeneous among healthy adults with respect to cell counts, subsets, and the levels of expression of monocyte-associated molecules. An increase in the "non-classical" (CD14(Lo/Neg) /CD16(+) ) monocyte subset or in the expression of CD11b or TLR2 have known diagnostic/prognostic implications. CD244 and CD4 have well-defined functions on lymphocytes but perform unknown activities on monocytes although their expression appears more narrowly controlled. Together, these data suggest that monocytes should be more extensively examined in both clinical and basic contexts.

Genetic polymorphisms in innate immunity receptors do not predict the risk of bacterial and fungal infections and acute rejection after liver transplantation

INTRODUCTION

We studied the influence of a broad range of genetic variants in recipient and donor innate immunity receptors on bacterial and fungal infections and acute rejection after liver transplantation (LT).

METHODS

Seventy-six polymorphisms in TLR 1-10, NOD2, LBP, CD14, MD2, SIGIRR, Ficolins 1, -2, and -3, MASP 1, -2, and -3, and the complement receptor C1qR1 were determined in 188 LT recipients and 135 of their donors. Associations with clinically significant infections and acute rejection were analyzed for 50 polymorphisms. Significant associations were validated in an independent cohort of 181 recipients and 167 donors.

RESULTS

Three recipient polymorphisms and 3 donor polymorphisms were associated with infections in the identification cohort, but none of these associations were confirmed in the validation cohort. Three donor polymorphisms were associated with acute rejection in the identification cohort, but not in the validation cohort.

CONCLUSION

In contrast to their effect in the general population, 50 common genetic variations in innate immunity receptors do not influence susceptibility to bacterial/fungal infections after LT. In addition, no reproducible associations with acute rejection after LT were observed. Likely, transplant-related factors play a superior role as risk factors for bacterial/fungal infections and acute rejection after LT.

Induction of alloimmune tolerance in heart transplantation through gene silencing of TLR adaptors

Toll-like receptors (TLRs) activate biochemical pathways that evoke activation of innate immunity, which leads to dendritic cell (DC) maturation and initiation of adaptive immune responses that provoke allograft rejection. We aimed to prolong allograft survival by selectively inhibiting expression of the common adaptors of TLR signaling, namely MyD88 and TRIF, using siRNA. In vitro we demonstrated that blocking expression of MyD88 and TRIF led to reduced DC maturation. In vivo treatment of recipients with MyD88 and TRIF siRNA significantly prolonged allograft survival in the BALB/c > C57BL6 cardiac transplant model. Moreover, the combination of MyD88 and TRIF siRNA along with a low dose of rapamycin further extended the allograft survival (88.8 ± 7.1 days). Tissue histopathology demonstrated an overall reduction in lymphocyte interstitium infiltration, vascular obstruction and hemorrhage in mice treated with MyD88 and TRIF siRNA vector plus rapamycin. Furthermore, treatment was associated with an increase in the numbers of CD4(+) CD25(+) FoxP3(+) regulatory T cells and Th2 deviation. To our knowledge, this study is the first demonstration of prolonging the survival of allogeneic heart grafts through gene silencing of TLR signaling adaptors, highlighting the therapeutic potential of siRNA in clinical transplantation.