Profiling sirolimus-induced inflammatory syndrome: a prospective tricentric observational study

Rapamycin Exacerbates Staphylococcus aureus Pneumonia by Inhibiting mTOR-RPS6 in Macrophages

Purpose

This study aimed to explore the effect of Rapamycin (Rapa) in Staphylococcus aureus (S. aureus) pneumonia and clarify its possible mechanism.

Methods

We investigated the effects of Rapa on S. aureus pneumonia in mouse models and in macrophages cultured in vitro. Two possible mechanisms were investigated: the mTOR-RPS6 pathway phosphorylation and phagocytosis. Furthermore, for the mechanism verification in vivo, mice with specific Mtor knockout in myeloid cells were constructed for pneumonia models.

Results

Rapa exacerbated S. aureus pneumonia in mouse models, promoting chemokines secretion and inflammatory cells infiltration in lung. In vitro, Rapa upregulated the secretion of chemokines and cytokines in macrophages induced by S. aureus. Mechanistically, the mTOR-ribosomal protein S6 (RPS6) pathway in macrophages was phosphorylated in response to S. aureus infection, and the inhibition of RPS6 phosphorylation upregulated the inflammation level. However, Rapa did not increase the phagocytic activity. Accordingly, mice with specific Mtor knockout in myeloid cells experienced more severe S. aureus pneumonia.

Conclusion

Rapa exacerbates S. aureus pneumonia by increasing the inflammatory levels of macrophages. Inhibition of mTOR-RPS6 pathway upregulates the expression of cytokines and chemokines in macrophages, thus increases inflammatory cells infiltration and exacerbates tissue damage.

Absence of Mortality Differences Between the First and Second COVID-19 Waves in Kidney Transplant Recipients

Introduction

SARS-CoV-2 pandemic evolved in 2 consecutive waves during 2020. Improvements in the management of COVID-19 led to a reduction in mortality rates among hospitalized patients during the second wave. Whether this progress benefited kidney transplant recipients (KTRs), a population particularly vulnerable to severe COVID-19, remained unclear.

Methods

In France, 957 KTRs were hospitalized for COVID-19 in 2020 and their data were prospectively collected into the French Solid Organ Transplant (SOT) COVID registry. The presentation, management, and outcomes of the 359 KTRs diagnosed during the first wave were compared to those of the 598 of the second wave.

Results

Baseline comorbidities were similar between KTRs of the 2 waves. Maintenance immunosuppression was reduced in most patients but withdrawal of antimetabolite (73.7% vs. 58.4%, P < 0.001) or calcineurin inhibitor (32.1% vs. 16.6%, P < 0.001) was less frequent during the second wave. Hydroxychloroquine and azithromycin that were commonly used during the first wave (21.7% and 30.9%, respectively) but were almost abandoned during the second wave. In contrast, the use of high dose corticosteroids doubled (19.5% vs. 41.6%, P < 0.001). Despite these changing trends in COVID-19 management, 60-day mortality was not statistically different between the 2 waves (25.3% vs. 23.9%; Log Rank, P = 0.48) and COVID-19 hospitalization period was not associated with death due to COVID-19 in multivariate analysis (Hazard ratio 0.89, 95% confidence interval 0.67–1.17, P = 0.4).

Conclusion

We conclude that changing of therapeutic trends during 2020 did not reduce COVID-19 related mortality among KTRs. Our data indirectly support the importance of vaccination and neutralizing monoclonal anti-SARS-CoV-2 antibodies to protect KTRS from severe COVID-19.

Clinically available immunosuppression averts rejection but not systemic inflammation after porcine islet xenotransplant in cynomolgus macaques

A safe, efficacious, and clinically applicable immunosuppressive regimen is necessary for islet xenotransplantation to become a viable treatment option for diabetes. We performed intraportal transplants of wild-type adult porcine islets in 25 streptozotocin-diabetic cynomolgus monkeys. Islet engraftment was good in 21, partial in 3, and poor in 1 recipient. Median xenograft survival was 25 days with rapamycin and CTLA4Ig immunosuppression. Adding basiliximab induction and maintenance tacrolimus to the base regimen significantly extended median graft survival to 147 days (p < .0001), with three animals maintaining insulin-free xenograft survival for 265, 282, and 288 days. We demonstrate that this regimen suppresses non-Gal anti-pig antibody responses, circulating effector memory T cell expansion, effector function, and infiltration of the graft. However, a chronic systemic inflammatory state manifested in the majority of recipients with long-term graft survival indicated by increased neutrophil to lymphocyte ratio, IL-6, MCP-1, CD40, and CRP expression. This suggests that this immunosuppression regimen fails to regulate innate immunity and resulting inflammation is significantly associated with increased incidence and severity of adverse events making this regimen unacceptable for translation. Additional studies are needed to optimize a maintenance regimen for regulating the innate inflammatory response.

Sirolimus is effective in autoimmune lymphoproliferative syndrome-type III: A pedigree case report with homozygous variation PRKCD

Autoimmune lymphoproliferative syndrome (ALPS) usually presents in childhood with fever, nonmalignant splenomegaly, and lymphadenopathy along with cytopenia, which is caused by mutations in the FAS apoptotic pathway. The TCRαβ + CD4/CD8 double-negative T cells (DNT), one of required criteria of ALPS, will rise markedly in ALPS. Human Protein kinase C delta (PRKCD) deficiency (OMIM # 615559) was recently identified to be causative for an ALPS-type III with significant B-cell proliferation particularly of immature B cells. We report a pedigree homozygous variation of PRKCD gene (c.36T>G, p. Y12X) which presented with refractory cytopenia, splenomegaly, and polarization of DNT/regulatory T cells (Treg) axis. After repeated recurrence, the patient was treated with mTOR inhibitor sirolimus, which had a safety mechanism and specifically rebalance the DNT/Treg axis. The patient's hemoglobin and clinical condition improved gradually by the application of sirolimus (1.5 mg/m², actual blood concentration 4.27-10.3 ng/l). Homozygous variation in PRKCD may lead to typical ALPS clinical manifestations. Targeting DNT/Treg axis, use of sirolimus in such patients may help to achieve good clinical control.

Tacrolimus- versus sirolimus-based immunosuppression after simultaneous pancreas and kidney transplantation: 5-year results of a randomized trial

Tacrolimus, the cornerstone immunosuppression after simultaneous pancreas and -kidney (SPK) transplantation, may exert nephrotoxic and diabetogenic effects. We therefore prospectively compared in an open-label, randomized, monocentric, 5-year follow-up study, a tacrolimus- and a sirolimus-based immunosuppressive regimen. Randomization using the block method allowing a blind allocation was done at the time of surgery. All patients received anti-thymocyte globulin and maintenance therapy with tacrolimus, mycophenolate mofetil, and steroids. At month 3, tacrolimus was continued or replaced by sirolimus. The primary endpoint was kidney and pancreas graft survival at 1 and 5 years. Fifty patients were included in the final analysis in each group. At 1 year, differences for kidney and pancreas graft survival between sirolimus and tacrolimus were 0% (90% confidence interval -4.61% to 4.61%) and 6% (90% confidence interval -6.32% to 18.32%), respectively. There was no difference in renal and pancreas graft survival at 5 years. Thirty-four patients (68%) in the sirolimus group vs three (6%) in the tacrolimus group needed definitive withdrawal of the study drug. Despite noninferiority of sirolimus compared to tacrolimus for kidney and pancreas graft survival, the high rate of sirolimus discontinuation does not favor its use as cornerstone therapy after SPK transplantation (NCT00693446).

mTOR direct crosstalk with STAT5 promotes de novo lipid synthesis and induces hepatocellular carcinoma

Hepatocellular carcinoma (HCC) can be the last step of nonalcoholic fatty liver disease (NAFLD) evolution, and the main characteristic of NAFLD is alteration in lipid metabolism. However, the mechanisms of abnormal lipid metabolism in NAFLD and HCC progression are yet to be identified. Here, we demonstrate that liver-specific activation of mTORC1 promoted the expression of lipid synthesis genes and lead to the development of spontaneous HCC. Genetic mouse models developed spontaneous HCC along with increased expressions of SREBP1, ACC1 and FASN. In addition, high levels of p-STAT5 were observed in the livers and particularly evident in the tumor area. And the synthesis of p-STAT5 was increased in patients along with the increase in SREBP1 synthesis in clinical samples. Moreover, mTORC1 interacts with and phosphorylates the STAT5 in hepatocytes. In conclusion, our data suggested that mTORC1 upregulates SREBP1 transcription via crosstalk with the STAT5 pathway which contributes to the NAFLD-related HCC pathogenesis. And the inhibitor of SREBP1 and mTOR may help to prevent HCC in clinical NAFLD patients.

Mammalian Target of Rapamycin: Is It Relevant to COPD Pathogenesis or Treatment?

The mammalian target of rapamycin (mTOR) signalling pathway regulates fundamental metabolic processes such as inflammation, autophagy and apoptosis, all of which influence cell fate. Recent experimental data suggest that mTOR signalling is involved in many diseases, including lung diseases, but with contrasting data. Overexpression of mTOR and its signalling proteins have been linked to lung cell senescence and development of emphysema, pulmonary hypertension and inflammation. On the other hand, mTOR inhibitors, as rapamycin and/or its derivatives, restore corticosteroid sensitivity in peripheral blood mononuclear cells from chronic obstructive pulmonary disease (COPD) patients, and overexpression of mTOR suppresses cigarette smoke-induced inflammation and emphysema, suggesting that induction of mTOR expression/activity might be useful to treat COPD. This apparent discrepancy is due to complex and heterogenic enzymatic pathway of mTOR. Translation of pre-clinical positive data on the use of mTOR inhibitors to COPD therapy needs a more in-depth knowledge of mTOR signalling.

mTOR inhibitors and risk of chronic antibody-mediated rejection after kidney transplantation: where are we now?

Antibody-mediated rejection (AMR) usually starts with generation of donor-specific anti-HLA antibodies (DSAs), arising from a B-cell response to antigen recognition. In vitro and preclinical data demonstrate that mammalian target of rapamycin (mTOR) inhibition attenuates the mTOR-mediated intracellular signaling pathway involved in AMR-related kidney damage. The limited available data from immunological studies in kidney transplant patients, however, have not shown such effects in vivo. In terms of clinical immunosuppression, the overriding influence on rates of de novo DSA (dnDSA) or AMR-regardless of the type of regimen-is patient adherence. To date, limited data from patients given mTOR inhibitor therapy with adequate concurrent immunosuppression, such as reduced-exposure calcineurin inhibitor (CNI) therapy, have not shown an adverse effect on the risk of dnDSA or AMR. Early switch to an mTOR inhibitor (<6-12 months post-transplant) in a CNI-free regimen, in contrast, can increase the risk of dnDSA, especially if adjunctive therapy is inadequate. Late conversion to CNI-free therapy with mTOR inhibition does not appear to affect the risk of dnDSA. More data, from prospective studies, are required to fully understand that association between use of mTOR inhibitors with different types of concomitant therapy and risk of dnDSA and AMR.

Emerging Perspectives on mTOR Inhibitor-Associated Pneumonitis in Breast Cancer

Substantial improvements in the early detection and treatment of breast cancer have led to improvements in survival, but breast cancer remains a significant cause of morbidity and mortality in women. In 2012, the mammalian target of rapamycin (mTOR) inhibitor everolimus was approved by the U.S. Food and Drug Administration for the treatment of advanced breast cancer in patients resistant to endocrine therapy. Although everolimus is generally well tolerated, mTOR inhibitor-associated pneumonitis is one of the most common adverse drug events leading to treatment discontinuation. To date, the underlying pathophysiology of this toxicity is unclear, and this uncertainty may hinder the optimization of management strategies. However, experiences from breast cancer and renal cell carcinoma clinical trials indicate that mTOR inhibitor-associated pneumonitis can be effectively managed by early detection, accurate diagnosis, and prompt intervention that generally involves everolimus dose reductions, interruptions, or discontinuation. Management can be achieved by a multidisciplinary approach that involves the collaborative efforts of nurses, oncologists, radiologists, infectious disease specialists, pulmonologists, clinical pharmacists, and pathologists. Comprehensive education must be provided to all health care professionals involved in managing patients receiving everolimus therapy. Although general recommendations on the management of mTOR inhibitor-associated pneumonitis have been published, there is a lack of consensus on the optimal management of this potentially serious complication. This article provides an overview of mTOR inhibitor-associated pneumonitis, with a focus on the detection, accurate diagnosis, and optimal management of this class-related complication of mTOR inhibitor therapy.

IMPLICATIONS FOR PRACTICE

This article summarizes the pathogenesis, clinical presentation, incidence, detection, and optimal management of everolimus-related noninfectious pneumonitis in breast cancer. In particular, this article provides a detailed overview of the important aspects of the detection, accurate diagnosis, and appropriate management of mammalian target of rapamycin inhibitor-associated pneumonitis. In addition, this article emphasizes that effective management of this adverse drug event in patients with breast cancer will require a multidisciplinary approach and collaboration among various health care professionals.

mTOR masters monocyte development in bone marrow by decreasing the inhibition of STAT5 on IRF8

Monocytes and macrophages play a key role in defending pathogens, removing the dead cells or cell debris, and wound healing. The mammalian target of rapamycin (mTOR) inhibitor rapamycin (RPM) is widely used in clinics to treat patients with organ transplantation or tumors. The role of mTOR in monocyte/macrophage development remains to be clarified. Here we found that mTOR intrinsically controls monocyte/macrophage development, as evidenced by the decreased percentages and cell numbers of CD11b⁺F4/80⁺ cells resulting from mTOR inhibition in SCID mice, mTOR-deficient mice, and mixed chimera mice, and the in vitro colony formation and monocyte/macrophage induction assays. However, Lyzs-mTOR knockout mice displayed normal levels of monocytes/macrophages, indicating that mTOR is not essential for the survival and maturation of monocytes/macrophages. Further studies showed that mTOR deficiency significantly reduced macrophage colony-stimulating factor receptor CD115 expression at the transcriptional and translational levels. The molecular mechanism studies indicate that the impaired monocyte/macrophage development caused by mTOR deficiency is mainly a result of the overactivated STAT5 and subsequent downregulation of IRF8, but not the altered cell metabolism and autophagy. Therefore, our work identifies that mTOR is an intrinsic master for monocyte/macrophage development at the early stages through regulating STAT5-IRF8-dependent CD115-expressing pathway. Long-term usage of RPM may cause a defect of myeloid progenitors in bone marrow.

A randomized control trial to establish the feasibility and safety of rapamycin treatment in an older human cohort: Immunological, physical performance, and cognitive effects

Inhibition of the mechanistic target of rapamycin (mTOR) pathway by rapamycin (RAPA), an FDA-approved immunosuppressive drug used as a clinical therapy to prevent solid organ allograft rejection, enhances longevity in mice. Importantly, RAPA was efficacious even when initiated in relatively old animals, suggesting that mTOR inhibition could potentially slow the progression of aging-associated pathologies in older humans (Harrison et al., 2009; Miller et al., 2011). However, the safety and tolerability of RAPA in older human subjects have not yet been demonstrated. Towards this end, we undertook a placebo-controlled pilot study in 25 generally healthy older adults (aged 70-95 years); subjects were randomized to receive either 1 mg RAPA or placebo daily. Although three subjects withdrew, 11 RAPA and 14 controls completed at least 8 weeks of treatment and were included in the analysis. We monitored for changes that would indicate detrimental effects of RAPA treatment on metabolism, including both standard clinical laboratory assays (CBC, CMP, HbA1c) and oral glucose tolerance tests (OGTTs). We also monitored parameters typically associated with aging that could potentially be modified by RAPA; these included cognitive function which was assessed by three different tools: Executive Interview-25 (EXIT25); Saint Louis University Mental Status Exam (SLUMS); and Texas Assessment of Processing Speed (TAPS). In addition, physical performance was measured by handgrip strength and 40-foot timed walks. Lastly, changes in general parameters of healthy immune aging, including serum pro-inflammatory cytokine levels and blood cell subsets, were assessed. Five subjects reported potential adverse side effects; in the RAPA group, these were limited to facial rash (1 subject), stomatitis (1 subject) and gastrointestinal issues (2 subjects) whereas placebo treated subjects only reported stomatitis (1 subject). Although no other adverse events were reported, statistically significant decrements in several erythrocyte parameters including hemoglobin (HgB) and hematocrit (Hct) as well as in red blood cell count (RBC), red blood cell distribution width (RDW), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) were observed in the RAPA-treatment group. None of these changes manifested clinically significant effects during the short duration of this study. Similarly, no changes were noted in any other clinical laboratory, cognitive, physical performance, or self-perceived health status measure over the study period. Immune parameters were largely unchanged as well, possibly due to the advanced ages of the cohort (70-93 years; mean age 80.5). RAPA-associated increases in a myeloid cell subset and in T_REGS were detected, but changes in most other PBMC cell subsets were not statistically significant. Importantly, the OGTTs revealed no RAPA-induced change in blood glucose concentration, insulin secretion, and insulin sensitivity. Thus, based on the results of our pilot study, it appears that short-term RAPA treatment can be used safely in older persons who are otherwise healthy; a trial with a larger sample size and longer treatment duration is warranted.

Mammalian Target of Rapamycin: A Target for (Lung) Diseases and Aging

The mammalian target of rapamycin (mTOR) signaling pathway has been studied in the context of an impressive number of biological processes and disease states, including major diseases of the lung such as idiopathic pulmonary fibrosis and chronic obstructive pulmonary disease, as well as the rare condition lymphangioleiomyomatosis. The involvement of mTOR in so many disease states (in and out of the lung) raises the question how one signaling pathway can have overlapping but diverse roles seemingly everywhere. Findings in the last decade have placed the mTOR pathway in a new context as an important, conserved mediator of the aging process. This offers one explanation for the pleiotropic effects of mTOR: -that many chronic diseases are also diseases of aging and that pathways modulating aging will have widespread effects on associated disease. However, this may not be the entire story, because mTOR is also implicated in a large number of diseases not linked to aging. In this article, we discuss the current state of knowledge regarding mTOR, especially in the context of lung pathologies, and offer a potential explanation for its widespread involvement in human disease.

Liver damage, inflammation, and enhanced tumorigenesis after persistent mTORC1 inhibition

Obesity can result in insulin resistance, hepatosteatosis, and nonalcoholic steatohepatitis (NASH) and increases liver cancer risk. Obesity-induced insulin resistance depends, in part, on chronic activation of mammalian target of rapamycin complex 1 (mTORC1), which also occurs in human and mouse hepatocellular carcinoma (HCC), a frequently fatal liver cancer. Correspondingly, mTORC1 inhibitors have been considered as potential NASH and HCC treatments. Using a mouse model in which high-fat diet enhances HCC induction by the hepatic carcinogen DEN, we examined whether mTORC1 inhibition attenuates liver inflammation and tumorigenesis. Notably, rapamycin treatment or hepatocyte-specific ablation of the specific mTORC1 subunit Raptor resulted in elevated interleukin-6 (IL-6) production, activation of signal transducer and activator of transcription 3 (STAT3), and enhanced HCC development, despite a transient reduction in hepatosteatosis. These results suggest that long-term rapamycin treatment, which also increases IL-6 production in humans, is unsuitable for prevention or treatment of obesity-promoted liver cancer.

Immune responses of macrophages and dendritic cells regulated by mTOR signalling

The innate myeloid immune system is a complex network of cells that protect against disease by identifying and killing pathogens and tumour cells, but it is also implicated in homoeostatic mechanisms such as tissue remodelling and wound healing. Myeloid phagocytes such as monocytes, macrophages or dendritic cells are at the basis of controlling these immune responses in all tissues of the body. In the present review, we summarize recent studies demonstrating that mTOR [mammalian (or mechanistic) target of rapamycin] regulates innate immune reactions in macrophages and dendritic cells. The mTOR pathway serves as a decision maker to control the cellular response to pathogens and tumours by regulating the expression of inflammatory mediators such as cytokines, chemokines or interferons. In addition to various in vivo mouse models, kidney transplant patients under mTOR inhibitor therapy allowed the elucidation of important innate immune functions regulated by mTOR in humans. The role of the mTOR pathway in macrophages and dendritic cells enhances our understanding of the immune system and suggests new therapeutic avenues for the regulation of pro- versus anti-inflammatory mediators with potential relevance to cancer therapy, the design of novel adjuvants and the control of distinct infectious and autoimmune diseases.

Systemic and nonrenal adverse effects occurring in renal transplant patients treated with mTOR inhibitors

The mammalian target of rapamycin inhibitors (mTOR-I), sirolimus and everolimus, are immunosuppressive drugs largely used in renal transplantation. The main mechanism of action of these drugs is the inhibition of the mammalian target of rapamycin (mTOR), a regulatory protein kinase involved in lymphocyte proliferation. Additionally, the inhibition of the crosstalk among mTORC1, mTORC2, and PI3K confers the antineoplastic activities of these drugs. Because of their specific pharmacological characteristics and their relative lack of nephrotoxicity, these inhibitors are valid option to calcineurine inhibitors (CNIs) for maintenance immunosuppression in renal transplant recipients with chronic allograft nephropathy. However, as other immunosuppressive drugs, mTOR-I may induce the development of several adverse effects that need to be early recognized and treated to avoid severe illness in renal transplant patients. In particular, mTOR-I may induce systemic nonnephrological side effects including pulmonary toxicity, hematological disorders, dysmetabolism, lymphedema, stomatitis, cutaneous adverse effects, and fertility/gonadic toxicity. Although most of the adverse effects are dose related, it is extremely important for clinicians to early recognize them in order to reduce dosage or discontinue mTOR-I treatment avoiding the onset and development of severe clinical complications.