Lactate, histone lactylation and cancer hallmarks

Histone lactylation, an indicator of lactate level and glycolysis, has intrinsic connections with cell metabolism that represents a novel epigenetic code affecting the fate of cells including carcinogenesis. Through delineating the relationship between histone lactylation and cancer hallmarks, we propose histone lactylation as a novel epigenetic code priming cells toward the malignant state, and advocate the importance of identifying novel therapeutic strategies or dual-targeting modalities against lactylation toward effective cancer control. This review underpins important yet less-studied area in histone lactylation, and sheds insights on its clinical impact as well as possible therapeutic tools targeting lactylation.

How can aging be reversed? Exploring rejuvenation from a damage-based perspective

Advanced age is associated with accumulation of damage and other deleterious changes and a consequential systemic decline of function. This decline affects all organs and systems in an organism, leading to their inadaptability to the environment, and therefore is thought to be inevitable for humans and most animal species. However, in vitro and in vivo application of reprogramming strategies, which convert somatic cells to induced pluripotent stem cells, has demonstrated that the aged cells can be rejuvenated. Moreover, the data and theoretical considerations suggest that reversing the biological age of somatic cells (from old to young) and de-differentiating somatic cells into stem cells represent two distinct processes that take place during rejuvenation, and thus they may be differently targeted. We advance a stemness-function model to explain these data and discuss a possibility of rejuvenation from the perspective of damage accumulation. In turn, this suggests approaches to achieve rejuvenation of cells in vitro and in vivo.

Delivery of Rapamycin Using In Situ Forming Implants Promotes Immunoregulation and Vascularized Composite Allograft Survival

Vascularized composite allotransplantation (VCA), such as hand and face transplantation, is emerging as a potential solution in patients that suffered severe injuries. However, adverse effects of chronic high-dose immunosuppression regimens strongly limit the access to these procedures. In this study, we developed an in situ forming implant (ISFI) loaded with rapamycin to promote VCA acceptance. We hypothesized that the sustained delivery of low-dose rapamycin in proximity to the graft may promote graft survival and induce an immunoregulatory microenvironment, boosting the expansion of T regulatory cells (T_reg). In vitro and in vivo analysis of rapamycin-loaded ISFI (Rapa-ISFI) showed sustained drug release with subtherapeutic systemic levels and persistent tissue levels. A single injection of Rapa-ISFI in the groin on the same side as a transplanted limb significantly prolonged VCA survival. Moreover, treatment with Rapa-ISFI increased the levels of multilineage mixed chimerism and the frequency of T_reg both in the circulation and VCA-skin. Our study shows that Rapa-ISFI therapy represents a promising approach for minimizing immunosuppression, decreasing toxicity and increasing patient compliance. Importantly, the use of such a delivery system may favor the reprogramming of allogeneic responses towards a regulatory function in VCA and, potentially, in other transplants and inflammatory conditions.

mTOR signalling: jack-of-all-trades 1

The mechanistic target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase that senses and integrates environmental information into cellular regulation and homeostasis. Accumulating evidence has suggested a master role of mTOR signalling in many fundamental aspects of cell biology and organismal development. mTOR deregulation is implicated in a broad range of pathological conditions, including diabetes, cancer, neurodegenerative diseases, myopathies, inflammatory, infectious, and autoimmune conditions. Here, we review recent advances in our knowledge of mTOR signalling in mammalian physiology. We also discuss the impact of mTOR alteration in human diseases and how targeting mTOR function can treat human diseases.

A randomized controlled trial to establish effects of short-term rapamycin treatment in 24 middle-aged companion dogs

Age is the single greatest risk factor for most causes of morbidity and mortality in humans and their companion animals. As opposed to other model organisms used to study aging, dogs share the human environment, are subject to similar risk factors, receive comparable medical care, and develop many of the same age-related diseases humans do. In this study, 24 middle-aged healthy dogs received either placebo or a non-immunosuppressive dose of rapamycin for 10 weeks. All dogs received clinical and hematological exams before, during, and after the trial and echocardiography before and after the trial. Our results showed no clinical side effects in the rapamycin-treated group compared to dogs receiving the placebo. Echocardiography suggested improvement in both diastolic and systolic age-related measures of heart function (E/A ratio, fractional shortening, and ejection fraction) in the rapamycin-treated dogs. Hematological values remained within the normal range for all parameters studied; however, the mean corpuscular volume (MCV) was decreased in rapamycin-treated dogs. Based on these results, we will test rapamycin on a larger dog cohort for a longer period of time in order to validate its effects on cardiac function and to determine whether it can significantly improve healthspan and reduce mortality in companion dogs.

Impact of rapamycin on status epilepticus induced hippocampal pathology and weight gain

Growing evidence implicates the dentate gyrus in temporal lobe epilepsy (TLE). Dentate granule cells limit the amount of excitatory signaling through the hippocampus and exhibit striking neuroplastic changes that may impair this function during epileptogenesis. Furthermore, aberrant integration of newly-generated granule cells underlies the majority of dentate restructuring. Recently, attention has focused on the mammalian target of rapamycin (mTOR) signaling pathway as a potential mediator of epileptogenic change. Systemic administration of the mTOR inhibitor rapamycin has promising therapeutic potential, as it has been shown to reduce seizure frequency and seizure severity in rodent models. Here, we tested whether mTOR signaling facilitates abnormal development of granule cells during epileptogenesis. We also examined dentate inflammation and mossy cell death in the dentate hilus. To determine if mTOR activation is necessary for abnormal granule cell development, transgenic mice that harbored fluorescently-labeled adult-born granule cells were treated with rapamycin following pilocarpine-induced status epilepticus. Systemic rapamycin effectively blocked phosphorylation of S6 protein (a readout of mTOR activity) and reduced granule cell mossy fiber axon sprouting. However, the accumulation of ectopic granule cells and granule cells with aberrant basal dendrites was not significantly reduced. Mossy cell death and reactive astrocytosis were also unaffected. These data suggest that anti-epileptogenic effects of mTOR inhibition may be mediated by mechanisms other than inhibition of these common dentate pathologies. Consistent with this conclusion, rapamycin prevented pathological weight gain in epileptic mice, suggesting that rapamycin might act on central circuits or even peripheral tissues controlling weight gain in epilepsy.

[Delayed wound healing during therapy of cutaneous graft-versus-host disease with everolimus]

Graft-versus-host-disease (GvHD) is despite improvement in transplantation medicine the major cause for morbidity and mortality after allogeneic stem cell transplantation. We describe a patient with chronic cutaneous GvHD who developed massive skin ulcerations after changing the immunosuppressive therapy to a mammalian target of rapamycin (mTOR)-inhibitor.

Effects of rapamycin on granulation formation in response to centrally doubled coiled stents as a tracheal substitute

INTRODUCTION

In experiments involving tracheal wall defects in rabbits, metallic coil stents inevitably induce granulation formation in the defects. We examined the involvement of the mammalian target of rapamycin (mTOR) signaling pathway in granulation formation and examined the effects of rapamycin.

METHODS

The anterior half of the tracheal wall was removed for a longitudinal length of six tracheal rings. Metallic coils were placed into the tracheal lumen through a wall defect. The rabbits were sacrificed two months after undergoing an endoscopic examination, and the granulation tissue in the tracheal defects was removed for a Western blot analysis and immunohistochemical analysis. Rapamycin (0.5 mg kg(-1) day(-1)) was administered three times per week intramuscularly. The data were expressed as the relative expression versus the expression of actin.

RESULTS

The level of mTOR phosphorylation in the resected trachea was 0.72±0.45, and it significantly increased in the granulation tissue to 11.6±5.2, with concomitant increases in the phosphorylation levels of p70S6K and S6RP in all five rabbits. Although the systemic administration of rapamycin significantly decreased the levels of phosphorylated mTOR to 4.0±2.4 in the five treated rabbits, the clinical outcomes were unsatisfactory. Three of the five treated rabbits exhibited signs of wound complications, and wet granulation tissue that caused respiratory symptoms was found inside and outside of the coils in four rabbits.

CONCLUSIONS

Although rapamycin effectively reduced the mTOR activity in the granulation tissue, the granulation formation process seemed to be disturbed, most likely owing to the immunosuppressive effects of rapamycin.

Refractory autoimmune hemolytic anemia after intestinal transplant responding to conversion from a calcineurin to mTOR inhibitor

AIHA is a rare and serious complication of solid organ transplantation. Herein, we report four cases of warm or mixed AIHA in pediatric patients following combined liver, small bowel and pancreas transplant. The hemolysis was refractory to multiple treatment modalities including steroids, rituximab, IVIG, plasmapheresis, cytoxan, discontinuation of prophylactic penicillin, and a change in immunosuppression from tacrolimus to cyclosporine. All patients had resolution or marked improvement of hemolysis after discontinuation of maintenance of CNI and initiation of sirolimus immunosuppression. One patient developed nephrotic syndrome but responded to a change in immunosuppression to everolimus. Three of the four patients continue on immunosuppression with sirolimus or everolimus without further hemolysis, evidence of rejection or medication side effects. Based on our experience and review of similar cases in the literature, we have proposed a treatment algorithm for AIHA in the pediatric intestinal transplant patient population that recommends an early change in immunosuppressive regimen from CNIs to sirolimus therapy.