Septic shock is characterized by an excessive inflammatory response depicted in a cytokine storm that results from invasive bacterial, fungi, protozoa, and viral infections. Non-canonical inflammasome activation is crucial in the development of septic shock promoting pyroptosis and proinflammatory cytokine production via caspase-11 and gasdermin D (GSDMD). Here, we show that NAD + treatment protected mice toward bacterial and lipopolysaccharide (LPS)-induced endotoxic shock by blocking the non-canonical inflammasome specifically. NAD + administration impeded systemic IL-1β and IL-18 production and GSDMD-mediated pyroptosis of macrophages via the IFN-β/STAT-1 signaling machinery. More importantly, NAD + administration not only improved casp-11 KO (knockout) survival but rendered wild type (WT) mice completely resistant to septic shock via the IL-10 signaling pathway that was independent from the non-canonical inflammasome. Here, we delineated a two-sided effect of NAD + blocking septic shock through a specific inhibition of the non-canonical inflammasome and promoting immune homeostasis via IL-10, underscoring its unique therapeutic potential.

In clinical organ transplantation, donor and recipient ages may differ substantially. Old donor organs accumulate senescent cells that have the capacity to induce senescence in naïve cells. We hypothesized that the engraftment of old organs may induce senescence in younger recipients, promoting age-related pathologies. When performing isogeneic cardiac transplants between age-mismatched C57BL/6 old donor (18 months) mice and young and middle-aged C57BL/6 (3- or 12- month-old) recipients , we observed augmented frequencies of senescent cells in draining lymph nodes, adipose tissue, livers, and hindlimb muscles 30 days after transplantation. These observations went along with compromised physical performance and impaired spatial learning and memory abilities. Systemic levels of the senescence-associated secretory phenotype factors, including mitochondrial DNA (mt-DNA), were elevated in recipients. Of mechanistic relevance, injections of mt-DNA phenocopied effects of age-mismatched organ transplantation on accelerating aging. Single treatment of old donor animals with senolytics prior to transplantation attenuated mt-DNA release and improved physical capacities in young recipients. Collectively, we show that transplanting older organs induces senescence in transplant recipients, resulting in compromised physical and cognitive capacities. Depleting senescent cells with senolytics, in turn, represents a promising approach to improve outcomes of older organs.

Background:Obesity is widespread and linked to various co-morbidities. Bariatric surgery has been identified as the only effective treatment, promoting sustained weight loss and the remission of co-morbidities. Methods:Metabolic profiling was performed on diet-induced obese (DIO) mice, lean mice, and DIO mice that underwent sleeve gastrectomies (SGx). In addition, mice were subjected to intraperitoneal (i.p.) injections with taurodeoxycholic acid (TDCA) and valine. Indirect calorimetry was performed to assess food intake and energy expenditure. Expression of appetite-regulating hormones was assessed through quantification of isolated RNA from dissected hypothalamus tissue. Subsequently, i.p. injections with a melanin-concentrating hormone (MCH) antagonist and intrathecal administration of MCH were performed and weight loss was monitored. Results:Mass spectrometric metabolomic profiling revealed significantly reduced systemic levels of TDCA and L-valine in DIO mice. TDCA and L-valine levels were restored after SGx in both human and mice to levels comparable with lean controls. Systemic treatment with TDCA and valine induced a profound weight loss analogous to effects observed after SGx. Utilizing indirect calorimetry, we confirmed reduced food intake as causal for TDCA/valine-mediated weight loss via a central inhibition of the MCH. Conclusions:In summary, we identified restored TDCA/valine levels as an underlying mechanism of SGx-derived effects on weight loss. Of translational relevance, TDCA and L-valine are presented as novel agents promoting weight loss while reversing obesity-associated metabolic disorders. Funding:This work has been supported in part by a grant from NIH (UO-1 A1 132898 to S.G.T., DP and MA). M.Q. was supported by the IFB Integrated Research and Treatment Centre Adiposity Diseases (Leipzig, Germany) and the German Research Foundation (QU 420/1-1). J.I. was supported by the Biomedical Education Program (BMEP) of the German Academic Exchange Service (DAAD). T.H. (HE 7457/1-1) and F.K. (KR 4362/1-1) were supported by the German Research Foundation (DFG). H.R.C.B. was supported the Swiss Society of Cardiac Surgery. Y.N. was supported by the Chinese Scholarship Council (201606370196) and Central South University. H.U., T.M. and R.M. were supported by the Osaka Medical Foundation. C.S.F. was supported by the German Research Foundation (DFG, SFB738, B3).

Sex-specific influences have been shown for a variety of diseases. Whether donor or recipient sex and sex hormone levels impact alloimmune responses remains unclear. In unifactorial and multifactorial analyses of more than 400 000 SRTR listed kidney transplant patients, we found that younger female recipients had an inferior death-censored graft survival that was independent of donor sex. In contrast, graft survival was superior in older female recipients, suggesting the impact of recipient sex hormones over chromosomal sex mismatches. Those clinical changes were delineated in experimental skin and heart transplant models showing a prolongation of graft survival in ovariectomized young female recipients. In contrast, graft survival was comparable in ovariectomized and naïve old female recipients. Young ovariectomized mice showed reduced amounts and a compromised T cell proliferation. Deprivation of female hormones dampened the production of interferon (IFN)-γ and interleukin (IL)-17+ by CD4+ T cells while augmenting systemic counts of Tregs. Increasing estradiol concentrations in vitro promoted the switch of naïve CD4+ T cells into Th1 cells; high physiological estradiol concentrations dampening Th1 responses, promoted Tregs, and prolonged graft survival. Thus, clinical observations demonstrate age-specific graft survival patterns in female recipients. Estrogen levels, in turn, impact the fate of T cell subsets, providing relevant and novel information on age- and sex-specific alloimmunity.

Age impacts alloimmunity. Effects of aging on T-cell metabolism and the potential to interfere with immunosuppressants have not been explored yet. Here, we dissected metabolic pathways of CD4+ and CD8+ T cells in aging and offer novel immunosuppressive targets. Upon activation, CD4+ T cells from old mice failed to exhibit adequate metabolic reprogramming resulting into compromised metabolic pathways, including oxidative phosphorylation (OXPHOS) and glycolysis. Comparable results were also observed in elderly human patients. Although glutaminolysis remained the dominant and age-independent source of mitochondria for activated CD4+ T cells, old but not young CD4+ T cells relied heavily on glutaminolysis. Treating young and old murine and human CD4+ T cells with 6-diazo-5-oxo-l-norleucine (DON), a glutaminolysis inhibitor resulted in significantly reduced IFN-γ production and compromised proliferative capacities specifically of old CD4+ T cells. Of translational relevance, old and young mice that had been transplanted with fully mismatched skin grafts and treated with DON demonstrated dampened Th1- and Th17-driven alloimmune responses. Moreover, DON diminished cytokine production and proliferation of old CD4+ T cells in vivo leading to a significantly prolonged allograft survival specifically in old recipients. Graft prolongation in young animals, in contrast, was only achieved when DON was applied in combination with an inhibition of glycolysis (2-deoxy-d-glucose, 2-DG) and OXPHOS (metformin), two alternative metabolic pathways. Notably, metabolic treatment had not been linked to toxicities. Remarkably, immunosuppressive capacities of DON were specific to CD4+ T cells as adoptively transferred young CD4+ T cells prevented immunosuppressive capacities of DON on allograft survival in old recipients. Depletion of CD8+ T cells did not alter transplant outcomes in either young or old recipients. Taken together, our data introduce an age-specific metabolic reprogramming of CD4+ T cells. Targeting those pathways offers novel and age-specific approaches for immunosuppression.

Obesity initiates a chronic inflammatory network linked to perioperative complications and increased acute rejection rates in organ transplantation. Bariatric surgery is the most effective treatment of obesity recommended for morbidly obese transplant recipients. Here, we delineated the effects of obesity and bariatric surgery on alloimmunity and transplant outcomes in diet-induced obese (DIO) mice. Allograft survival was significantly shorter in DIO-mice. When performing sleeve gastrectomies (SGx) prior to transplantation, we found attenuated T cell-derived alloimmune responses resulting in prolonged allograft survival. Administering taurodeoxycholic acid (TDCA) and valine, metabolites depleted in DIO-mice and restored through SGx, prolonged graft survival in DIO-mice comparable with SGx an dampened Th1 and Th17 alloimmune responses while Treg frequencies and CD4+ T cell-derived IL-10 production were augmented. Moreover, in recipient animals treated with TDCA/valine, levels of donor-specific antibodies had been reduced. Mechanistically, TDCA/valine restrained inflammatory M1-macrophage polarization through TGR5 that compromised cAMP signaling and inhibited macrophage-derived T cell activation. Consistently, administering a TGR5 agonist to DIO-mice prolonged allograft survival. Overall, we provide novel insights into obesity-induced inflammation and its impact on alloimmunity. Furthermore, we introduce TDCA/valine as a noninvasive alternative treatment for obese transplant patients.

Elderly organ transplant recipients have remained underrepresented in clinical trials, despite representing a rapidly growing population. Here, we assessed age-specific effects of CTLA4-Ig (cytotoxic T-lymphocyte antigen 4-Ig), a fusion protein blocking costimulatory signaling between antigen-presenting cells and T cells through CD28. Cardiac allografts in young mice (2-3 months) treated with CTLA4-Ig survived indefinitely, whereas 80% of old recipients (18 months) had lost their graft after 100 days. CTLA4-Ig was also significantly less effective in older recipients of skin transplants. CTLA4-Ig reduced CD4+ central memory and effector memory T cells and diminished systemic interferon-gamma levels only in young recipients. These differences corresponded to a reduced expression of CD28 on antigen-experienced CD4+ T cells in old mice. In support, adoptive transfer of old CD4+ T cells that were transfected with a lentiviral vector inducing constant expression of CD28 accelerated the rejection of allogeneic skin grafts in young RAG2-/- recipient mice. Regulatory T cells (Tregs), in contrast, demonstrated an increased expression of CD28 with aging and CTLA4-Ig treatment in old recipients resulted in reduced frequencies, compromised proliferation, and diminished suppressive capacity of Tregs. These findings may prove to have unique clinical consequences for immunosuppression in the growing population of elderly transplant recipients.

Jasper Iske, Timm Heinbokel, Ryoichi Maenosono, Yeqi Nian, Markus Quante, Koichiro Minami, Haruhito Azuma, Abdallah Elkhal, Stefan G. Tullius Department of Surgery, Brigham and Women’s Hospital, Boston, MA, United States; Institute of Transplant Immunology, Hannover Medical School, Hannover, Germany; Department of Nephrology, Charite Universitätsmedizin Berlin, Berlin, Germany; Department of Urology, Osaka Medical College, Osaka, Japan; Department of Kidney Transplantation, Tianjin First Central Hospital, Tianjin, People’s Republic of China; Department of Surgery, University Hospital Tuebingen, Tuebingen, Germany.

Uterus transplants (UTxs) have been performed worldwide. Overall frequencies have been low, but globally initiated UTx programs are expected to increase clinical implementation. The uterus constitutes a unique immunological environment with specific features of tissue renewal and a receptive endometrium. Decidual immune cells facilitate embryo implantation and placenta development. Although UTx adds to the complexity of immunity during pregnancy and transplantation, the procedure provides a unique clinical and experimental model. We posit that understanding the distinct immunological properties at the interface of the transplanted uterus, the fetus and maternal circulation might provide valuable novel insights while improving outcomes for UTx. Here, we discuss immunological challenges and opportunities of UTx affecting mother, pregnancy and healthy livebirths.

Older organs represent an untapped potential to close the gap between demand and supply in organ transplantation but are associated with age-specific responses to injury and increased immunogenicity, thereby aggravating transplant outcomes. Here we show that cell-free mitochondrial DNA (cf-mt-DNA) released by senescent cells accumulates with aging and augments immunogenicity. Ischemia reperfusion injury induces a systemic increase of cf-mt-DNA that promotes dendritic cell-mediated, age-specific inflammatory responses. Comparable events are observed clinically, with the levels of cf-mt-DNA elevated in older deceased organ donors, and with the isolated cf-mt-DNA capable of activating human dendritic cells. In experimental models, treatment of old donor animals with senolytics clear senescent cells and diminish cf-mt-DNA release, thereby dampening age-specific immune responses and prolonging the survival of old cardiac allografts comparable to young donor organs. Collectively, we identify accumulating cf-mt-DNA as a key factor in inflamm-aging and present senolytics as a potential approach to improve transplant outcomes and availability.

Introduction: Organ age is linked to an accumulation of senescent cells that induce a senescent phenotype in neighboring cells through alterations of the immune-micro-environment. Organ age has also been shown to augment alloimmune responses in recipients resulting into increased acute rejection rates. We hypothesized that senescent cells disseminate in recipients subsequent to the engraftment of older organs and postulated an acceleration in aging. Material and Methods: Hearts from either young or old C57BL/6 (2 and 18 months) were transplanted into syngeneic and allogeneic young recipients. Solid organs and lymphoid tissues were collected from donors and recipients at sequential intervals after engraftment, assessing the distribution of senescent cells and inflammatory products; systemic and local senescent associated secretory phenotype (SASP) derived molecules (mt-DNA, p16) were measured by qPCR. T cell and DC frequency and activation were tested by FACS and co-culturing experiments. Donors were treated with senolytics (Dasitinib & Quercetin) prior to organ procurement and cardiac transplantation into histoincompatible recipients. Results: We detected an increased frequency of senescent cells in hearts, kidneys and skin of old donor mice (mean= 8,21% vs 0,3% in organs from young animals). More importantly, young recipients of old cardiac allografts demonstrated increased frequencies of senescent cells (by post-operative day 30) localized in draining lymph nodes and livers (3,1-fold and 20.3 fold increase, p<0.01 and p<0.0001 compared to young recipients of young hearts); young recipients of old grafts also showed augmented systemic p16 levels indicating a spread of the senescent phenotype (3,45-fold increase, p< 0.05). As part of the SASP, isolated senescent cells released significantly increased amounts of mt-DNA (p<0.05) that augmented co-stimulatory molecule expression in old dendritic cells in-vitro enhancing Th17 and Th1 derived cytokine expression. Treatment of old donor animals with senolytics disabling senescence-associated anti-apoptotic pathways cleared senescent cells and reduced mt-DNA and p16 levels (p=0.01 compared to young controls). Moreover, senolytics restricted the expression of IFN-γ and IL-17 on CD4+ T cells (p=0.001) and prolonged the survival of old cardiac allografts significantly (p=0.02). Conclusion: The accumulation of senescent cells in old organs accelerated alloimmune responses through augmented mt-DNA levels. Notably, transplanting older organs promoted senescence in transplant recipients. Senolytics cleared senescent cells, dampened alloimmune responses and prolonged allograft survival. Those data may serve as a rationale to utilize senolytics to improve graft quality and survival of older organs. Moreover, senolytics may halt the spread of senescent cells in recipients of old organs.

Abnormalities of or reductions in GABAergic interneurons are implicated in the pathology of severe neuropsychiatric disorders, for which effective treatments are still elusive. Transplantation of human stem cell-derived interneurons is a promising cell-based therapy for treatment of these disorders. In mouse xenograft studies, human stem cell-derived-interneuron precursors could differentiate in vivo, but required a prolonged time of four to seven months to migrate from the graft site and integrate with the host tissue. This poses a serious roadblock for clinical translation of this approach. For transplantation to be effective, grafted neurons should migrate to affected areas at a faster rate. We have previously shown that endothelial cells of the periventricular vascular network are the natural substrates for GABAergic interneurons in the developing mouse forebrain, and provide valuable guidance cues for their long-distance migration. In addition, periventricular endothelial cells house a GABA signaling pathway with direct implications for psychiatric disease origin. In this study we translated this discovery into human, with significant therapeutic implications. We generated human periventricular endothelial cells, using human pluripotent stem cell technology, and extensively characterized its molecular, cellular, and functional properties. Co-culture of human periventricular endothelial cells with human interneurons significantly accelerated interneuron migration in vitro and led to faster migration and wider distribution of grafted interneurons in vivo, compared to neuron-only transplants. Furthermore, the co-transplantation strategy was able to rescue abnormal behavioral symptoms in a pre-clinical model of psychiatric disorder, within 1 month after transplantation. We anticipate this strategy to open new doors and facilitate exciting advances in angiogenesis-mediated treatment of psychiatric disorders.

Targeting T-cell metabolism may provide an effective immunosuppression. We delineated the correlation of aging and T cell metabolism. Moreover, we defined the consequences of metabolic changes in T-cell compartments on alloimmunity and delineated specific and novel immunosuppressive targets on CD-4+ T-cells. We collected naïve CD4+ T cells (splenocytes) of young and old (3 and 18 months) C67BL/6 mice. Following activation with anti-CD3 and anti-CD28 (24 hrs), we evaluated oxidative phosphorylation (OXPHOS) and aerobic glycolysis by oxygen consumption (OCR) and extracellular acidification (ECAR) using a Seahorse XFe96 extracellular flux analyzer. Graft survival, T-cell specificity and a detailed immune profiling were recorded serially. Upon activation in-vitro, a compromised utilization of OXPHOS and glycolysis pathways was observed in old CD4+ T cells (p<0.0001), indicating failure of old CD4+ T cells to exhibit adequate metabolic reprogramming. Further analysis of metabolic pathways revealed a critical role of glutaminolysis in T cell activation. 6-diazo-5-oxo-l-norleucine (DON), an analog of glutamine inhibiting critical enzymes of glutaminolysis resulted into an age-specific reduced activation and proliferative capacities of CD4+T cells. Notably, lower doses of DON inhibited IL-2 production and CFSE-determined proliferation only in old but not young CD4+ T cells (p<0.001). Utilizing a pre-clinical fully mismatched transplantation model, we observed inversed CD4:CD8 ratio in old recipients following DON (1.6mg/kg every other day). Graft survival was prolonged in young recipients, from 7 to 18 days (p< 0.01). Notably, was a drastic and age-specific effect of DON on graft skin graft survival in old recipients to 42 days (n=7, p<0.001). Targeting metabolic pathways was specific to CD4+ T-cells. Adoptively transferring young CD4+ T cells reversed the prolonged survival observed in old recipients. Depletion of CD8+ T cells did not alter transplant outcomes of DON in either young or old recipients. Taken together, we introduce a detailed and age-specific analysis of metabolic pathways in T cells and introduce a novel concept for an optimized immunosuppression in old recipients.