Early Cell Necrosis Research Articles

Antagonism between salicylate and the cAMP signal controls yeast cell survival and growth recovery from quiescence.

Aspirin and its main metabolite salicylate are promising molecules in preventing cancer and metabolic diseases. S. cerevisiae cells have been used to study some of their effects: (i) salicylate induces the reversible inhibition of both glucose transport and the biosyntheses of glucose-derived sugar phosphates, (ii) Aspirin/salicylate causes apoptosis associated with superoxide radical accumulation or early cell necrosis in MnSOD-deficient cells growing in ethanol or in glucose, respectively. So, treatment with (acetyl)-salicylic acid can alter the yeast metabolism and is associated with cell death. We describe here the dramatic effects of salicylate on cellular control of the exit from a quiescence state. The growth recovery of long-term stationary phase cells was strongly inhibited in the presence of salicylate, to a degree proportional to the drug concentration. At high salicylate concentration, growth reactivation was completely repressed and associated with a dramatic loss of cell viability. Strikingly, both of these phenotypes were fully suppressed by increasing the cAMP signal without any variation of the exponential growth rate. Upon nutrient exhaustion, salicylate induced a premature lethal cell cycle arrest in the budded-G2/M phase that cannot be suppressed by PKA activation. We discuss how the dramatic antagonism between cAMP and salicylate could be conserved and impinge common targets in yeast and humans. Targeting quiescence of cancer cells with stem-like properties and their growth recovery from dormancy are major challenges in cancer therapy. If mechanisms underlying cAMP-salicylate antagonism will be defined in our model, this might have significant therapeutic implications.

Acetaminophen hepatotoxicity and repair: the role of sterile inflammation and innate immunity

Acetaminophen (APAP) hepatotoxicity because of overdose is the most frequent cause of acute liver failure in the western world. Metabolic activation of APAP and protein adduct formation, mitochondrial dysfunction, oxidant stress, peroxynitrite formation and nuclear DNA fragmentation are critical intracellular events in hepatocytes. However, the early cell necrosis causes the release of a number of mediators such as high-mobility group box 1 protein, DNA fragments, heat shock proteins (HSPs) and others (collectively named damage-associated molecular patterns), which can be recognized by toll-like receptors on macrophages, and leads to their activation with cytokine and chemokine formation. Although pro-inflammatory mediators recruit inflammatory cells (neutrophils, monocytes) into the liver, neither the infiltrating cells nor the activated resident macrophages cause any direct cytotoxicity. In contrast, pro- and anti-inflammatory cytokines and chemokines can directly promote intracellular injury mechanisms by inducing nitric oxide synthase or inhibit cell death mechanisms by the expression of acute-phase proteins (HSPs, heme oxygenase-1) and promote hepatocyte proliferation. In addition, the newly recruited macrophages (M2) and potentially neutrophils are involved in the removal of necrotic cell debris in preparation for tissue repair and resolution of the inflammatory response. Thus, as discussed in detail in this review, the preponderance of experimental evidence suggests that the extensive sterile inflammatory response during APAP hepatotoxicity is predominantly beneficial by limiting the formation and the impact of pro-inflammatory mediators and by promoting tissue repair.

Monitoring efficacy of cryotherapy for superficial basal cell carcinomas with in vivo reflectance confocal microscopy: A preliminary study

Superficial BCCs (sBCCs) usually appear as multiple lesions in chronic sun-damaged skin of elderly people and may show a destructive growth if left untreated. Non-invasive treatment modalities, such as cryotherapy have been employed for sBCCs, all failing to provide tissue for confirming diagnosis and assessing adequacy of tumour removal. Reflectance confocal microscopy (RCM), a new non-invasive imaging technique has proven to be a useful tool for detection of basal cell carcinoma in vivo. To non-invasively assess efficacy of cryotherapy for sBCCs by cytomorphologic analysis using RCM. We examined 10 histologically proven sBCCs located on the trunk of 5 consecutive patients with a mean age of 84.6 years. SBCCs were frozen twice using a spray nitrogen cryoprobe. RCM imaging was performed in each sBCC before cryotherapy and after 5 and 24h to monitor resulting tissue injury. Distinct cytomorphologic characteristics were determined by three observers allowing non-invasive evaluation of therapeutic efficacy of treatment immediately after cryotherapy. Tumour clearance was assessed by RCM imaging 3 months after therapy followed by histopathologic examination. Characteristic RCM-features of BCC were present in all lesions before cryotherapy. Five hours after cryotherapy, all 10 sBCCs showed small bright round to polygonal structures at basal layer and black round to oval areas of varying size with such bright structures floating therein, correlating to cell necrosis and incipient blistering. Eight sBCCs showed also cell necrosis in upper dermis. After 24h all sBCCs showed necrotic cells beneath collagen bundles. Tumour clearance on later histopathologic examination was only proven in those lesions showing damage to the upper dermis after 5h with RCM. Early cell necrosis within upper dermal structures seems to correlate with ablation of overlying tumour tissue. When it is not produced by cryotherapy, a second treatment should be considered.

Intrasplenic hepatocyte transplantation: evaluation of DNA synthesis and proliferation in auxiliary transplanted cells.

The value of isolated hepatocyte transplantation as a temporary support in acute hepatic failure remains controversial regarding the functional capacities of freshly isolated and transplanted hepatocytes. To evaluate the survival rate of intrasplenically transplanted liver cells and their response to a proliferation stimulus like partial hepatectomy, 3H-thymidine incorporation into hepatic and auxiliary transplanted hepatocyte DNA was determined. The survival rate of intrasplenically transplanted hepatocytes was evaluated by analyses of m-albumin-RNA within the splenic tissue and compared to the morphological findings. The histological results show a marked decrease (greater than x 100) of intrasplenically transplanted hepatocytes within 1 week after injection. The amount of surviving cells then remained constant for 3 months without any signs of proliferation. After partial hepatectomy a stimulation of hepatic regeneration was observed in the remaining liver tissue but not in auxiliary transplanted hepatocytes. M-albumin-RNA determination of auxiliary transplanted hepatocytes revealed a decrease of m-albumin-RNA concentration of greater than 100 times within 24 h after transplantation indicating early cell necrosis of the transplanted cells. Since intrasplenically transplanted hepatocytes underwent an early cell necrosis without any evidence for a directly postoperatively inducible cell proliferation, it is concluded that a sufficient metabolic support in acute hepatic failure cannot be taken into consideration.

Morphological and functional changes during thyroid hyperplasia and involution in C3H Mice: evidence for folliculoneogenesis during involution.

Involution of thyroid hyperplasia was induced in C3H mice by discontinuing a goitrogenic treatment (low iodine diet supplemented with 0.25% propylthiouracil) and refeeding a normal iodine diet. Thyroid involution was studied by morphological, histochemical, autoradiographic, and stereological methods. The onset of the involution was characterized by an early accumulation of colloid, the presence of necrotic cells in the follicular lumina, and the appearance of homogeneous microcavities in the epithelial layers. The intraepithelial microcavities had the same morphological and functional properties as the follicular lumina. They were limited by a membrane covered with microvilli; polysaccharides and peroxidase activity were detected on their membranes, and 125I-labeling was marked in their lumina. Thin serial sections demonstrated that the microlumens originated from the intercellular space; plasma membranes differentiated into junctional complexes, and a narrow lumen limited by a membrane covered with short microvilli was formed in the intercellular space between the junctions. Later on, the newly formed microlumens fused to form new follicles with a cloverleaf pattern. As a consequence of the folliculogenesis, the total number of follicles doubled after 8 days of involution. This increase in number was mainly due to the presence of a population of small follicles. The folliculogenesis was associated in the first 4 days of involution with an active cellular multiplication which compensated for the early cell necrosis and led to a doubled number of epithelial cells. The increase in the total number of follicles and cells could partially explain the persistence of a relatively high thyroid weight after involution of hyperplasia.

Development of the metatarsophalangeal joint of the chick embryo: morphological, ultrastructural and histochemical studies.

The histogenesis and mechanism of joint clefting of the developing chick embryo up to the fifteenth day of incubation have been studied morphologically, ultrastructurally, and by histochemical methods. Cell degeneration was consistently noted 24 hours after differentiation of the joint tissue, and it is postulated that this early cell necrosis might account for the loosening of the medial part of articular mesenchyme (interzone) leading to differentiation of a three-layered embryonic joint. At the time of joint clefting degenerative cells were also seen in the peripheral parts of the developing articular cavity. In some cases clefting was immediately preceded and/or accompanied by the appearance of elongated, basophilic and electron-opaque cells closely arranged along the zone of tissue cleavage. These cells were thought to be implicated in some way in the clefting process and later to constitute a surface cell layer of articular cartilage. In addition to these observations clear morphological and histoautoradiographic evidence was found for the presence of an organic component, presumably mucopolysaccharide, in the primitive synovial fluid. Fluid secretion might also account for tissue cleavage at the sites of its accumulation. The data reported here suggest that joint cavity formation results from a combination of both intrinsic, genetically expressed and extrinsic mechanical factors acting synchronously.