Background & AimsThe gastrointestinal syndrome is an illness of the intestine caused by high levels of radiation. It is characterized by extensive loss of epithelial tissue integrity, which initiates a regenerative response by intestinal stem and precursor cells. The intestine has 24-hour rhythms in many physiological functions that are believed to be outputs of the circadian clock: a molecular system that produces 24-hour rhythms in transcription/translation. Certain gastrointestinal illnesses are worsened when the circadian rhythms are disrupted, but the role of the circadian clock in gastrointestinal regeneration has not been studied.MethodsWe tested the timing of regeneration in the mouse intestine during the gastrointestinal syndrome. The role of the circadian clock was tested genetically using the BMAL1 loss of function mouse mutant in vivo, and in vitro using intestinal organoid culture.ResultsThe proliferation of the intestinal epithelium follows a 24-hour rhythm during the gastrointestinal syndrome. The circadian clock runs in the intestinal epithelium during this pathologic state, and the loss of the core clock gene, BMAL1, disrupts both the circadian clock and rhythmic proliferation. Circadian activity in the intestine involves a rhythmic production of inflammatory cytokines and subsequent rhythmic activation of the JNK stress response pathway.ConclusionsOur results show that a circadian rhythm in inflammation and regeneration occurs during the gastrointestinal syndrome. The study and treatment of radiation-induced illnesses, and other gastrointestinal illnesses, should consider 24-hour timing in physiology and pathology.

A water-soluble formulation of CoQ10 (WS-CoQ10) was shown to stabilize mitochondria and prevent oxidative stress-induced neuronal death. Presenilin-1 (PS-1)-mutated Alzheimer's Disease (AD) fibroblasts (PSAF) were used for studying the effects of PS-1 mutation. PS-1 mutation correlated to increased reactive oxygen species (ROS) production and stress induced premature senescence (SIPS) in PSAF; WS-CoQ10 treatment decreased ROS generation, increased population doublings, and postponed SIPS. Treated PSAF had higher PCNA expression, and lower levels of MnSOD, p21, p16Ink4A, and Rb. WS-CoQ10 caused the resumption of autophagy in PSAF. Thus, WS-CoQ10 as inhibitor of SIPS and ameliorator of autophagy could be an effective prophylactic/therapeutic agent for AD.

The loss of circadian rhythms in the intestine leads to aberrant regulation of stem cell signaling pathways and increased tumor initiation.

Enhanced mitochondrial stability and decreased dependence on oxidative phosphorylation confer an acquired resistance to apoptosis in cancer cells, but may present opportunities for therapeutic intervention. The compound pancratistatin (PST) has been shown to selectively induce apoptosis in cancer cells. However, its low availability in nature has hindered its clinical advancement. We synthesized PST analogs and a medium-throughput screen was completed. Analogs SVTH-7, -6, and -5 demonstrated potent anti-cancer activity greater than PST and several standard chemotherapeutics. They disrupted mitochondrial function, activated the intrinsic apoptotic pathway, and reduced growth of tumor xenografts in vivo. Interestingly, the pro-apoptotic effects of SVTH-7 on cancer cells and mitochondria were abrogated with the inhibition of mitochondrial complex II and III, suggesting mitochondrial or metabolic vulnerabilities may be exploited by this analog. This work provides a scaffold for characterizing distinct mitochondrial and metabolic features of cancer cells and reveals several lead compounds with high therapeutic potential.

Regenerative capacity of skeletal muscle declines with age, the cause of which remains largely unknown. We investigated extracellular matrix (ECM) proteins and their regulators during early regeneration timepoints to define a link between aberrant ECM remodeling, and impaired aged muscle regeneration. The regeneration process was compared in young (three month old) and aged (18 month old) C56BL/6J mice at 3, 5, and 7 days following cardiotoxin-induced damage to the tibialis anterior muscle. Immunohistochemical analyses were performed to assess regenerative capacity, ECM remodeling, and the macrophage response in relation to plasminogen activator inhibitor-1 (PAI-1), matrix metalloproteinase-9 (MMP-9), and ECM protein expression. The regeneration process was impaired in aged muscle. Greater intracellular and extramyocellular PAI-1 expression was found in aged muscle. Collagen I was found to accumulate in necrotic regions, while macrophage infiltration was delayed in regenerating regions of aged muscle. Young muscle expressed higher levels of MMP-9 early in the regeneration process that primarily colocalized with macrophages, but this expression was reduced in aged muscle. Our results indicate that ECM remodeling is impaired at early time points following muscle damage, likely a result of elevated expression of the major inhibitor of ECM breakdown, PAI-1, and consequent suppression of the macrophage, MMP-9, and myogenic responses.