Evidence of caspase-3 activation in hyposmotic stress-induced necrosis

Red Light and 5% Aminolaevulinic Acid (5%) Inhibit Proliferation and Migration of Dysplastic Oral Keratinocytes via ROS Production: An In Vitro Study

Undiagnosed and untreated oral precancerous lesions often progress into malignancies. Photodynamic therapy (PDT) might be a minimally invasive alternative to conventional treatments. 5-aminolevulinic acid (5-ALA) is one of the most commonly used photosensitizers in PDT, and it is effective on many cancer types. However, its hydrophilic characteristic limits cell membrane crossing. In the present study, the effect of a newly formulated gel containing 5% 5-ALA in combination with red light (ALAD-PDT) on a premalignant oral mucosa cell line was investigated. The dysplastic oral keratinocyte (DOK) cells were incubated with ALAD at different concentrations (0.1, 0.5, 1, and 2 mM) at two different times, 45 min or 4 h, and then irradiated for 7 min with a 630 nm LED (25 J/cm2). MTT assay, flow cytometry, wound healing assay, and quantitative PCR (qPCR) were performed. ALAD-PDT exerted inhibitory effects on the proliferation and migration of DOK cells by inducing ROS and necrosis. mRNA analysis showed modulation of apoptosis-related genes' expression (TP53, Bcl-2, survivin, caspase-3, and caspase-9). Furthermore, there was no difference between the shorter and longer incubation times. In conclusion, the inhibitory effect of the ALAD-PDT protocol observed in this study suggests that ALAD-PDT could be a promising novel treatment for oral precancerous lesions.

Regulating the Membrane Transport Activity and Death of Cells via Electroosmotic Manipulation

Although the volume of living cells has been known to heavily influence their behavior and fate, a method allowing us to control the cell size in a programmable manner is still lacking. Here, we develop a technique in which precise changes in the cellular volume can be conveniently introduced by varying the voltage applied across a Nafion membrane that separates the culture medium from a reservoir. It is found that, unlike sudden osmotic shocks, active ion transport across the membrane of leukemia K562 cells will not be triggered by a gradual change in the extracellular osmolarity. Furthermore, when subjected to the same applied voltage, different lung and nasopharyngeal epithelial cancer cells will undergo larger volumetric changes and have a 5-10% higher death rate compared to their normal counterparts. We show that such distinct response is largely caused by the overexpression of aquaporin-4 in tumor cells, with knockout of this water channel protein resulting in a markedly reduced change in the cellular volume. Finally, by taking into account the exchange of water/ion molecules across the Nafion film and the cell membrane, a theoretical model is also proposed to describe the voltage-induced size changes of cells, which explain our experimental observations very well.

Cell death pattern in lens epithelium of cataract patients

PURPOSE

Apoptosis, a type of programmed cell death, is observed in various types of cataract and in cultured lens epithelium subjected to oxidative damage. We have recently described oxidative DNA base damage in epithelium in age-related cataract and cultured cells, and we here aimed to examine such epithelium for markers for proliferation, initiation of apoptosis and morphological patterns of cell damage.

METHODS

Samples (n = 75) were analysed by light microscopy/electron microscopy (LM/EM); immunohistochemistry (IHC) for PCNA and Ki67 (DNA synthesis/proliferation); TUNEL assay (DNA fragmentation/apoptosis); and protein/gene expression of Caspase-3 (apoptotic effector molecule) and BAX/Bcl2 (pro-/anti-apoptotic marker) in fresh/cultured epithelium by IHC and qRT-PCR.

RESULTS

In fresh samples, the majority of cells were Ki67-/PCNA+. BAX/BCL-2-ratio was approximately 1, and Caspase-3 levels were low. TUNEL stained scattered nuclei/nuclear fragments (9/6302 cells). Main morphological signs of cell damage included rupture of cell membranes and hydration of cytoplasm and nuclei. Cultivation increased levels of BAX and Bcl2 by IHC and qRT-PCR (approximately 10-fold upregulation). Caspase-3 levels remained low by IHC with similar expression in fresh and cultured samples by qRT-PCR.

CONCLUSION

Genomic stress and DNA repair may explain the contrasting expression of Ki67/PCNA in fresh epithelium. Despite low levels of Caspase-3 and similar expression of BAX/Bcl-2, a low incidence of apoptosis may be detected in epithelium in age-related corticonuclear cataract. Epithelium may be transferred to culture without an increase in expression of Caspase-3, one of the central mediators of apoptosis.

The olive leaf extract oleuropein exerts protective effects against oxidant-induced cell death, concurrently displaying pro-oxidant activity in human hepatocarcinoma cells

OBJECTIVES

Oleuropein (OP), the predominant natural constituent of leaves of the olive tree, exerts anti-inflammatory and antioxidant effects. The purpose of this study was to assess the protective effects of OP under the conditions of paraquat (PQ)-induced oxidative stress in vitro, using the human hepatocarcinoma cell line, HepG2.

METHODS

Cell viability and death were determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and 4',6-diamidino-2-phenylindole-propidium iodide staining, respectively. Superoxide anion and lipid peroxidation levels were evaluated using nitroblue tetrazolium and thiobarbituric acid-reactive substances assays, respectively. Apoptosis was assessed by measuring poly(ADP-ribose) polymerase (PARP) and caspase-3 (Casp-3) cleavage via immunoblotting and immunofluorescence analyses.

RESULTS

PQ induced a decrease in cellular viability by promoting necrosis through a mechanism involving superoxide generation and nuclear translocation of cleaved Casp-3. Co-treatment with OP afforded significant protection against the suppressive effects of PQ, as evident from increased cell viability, reduction of Casp-3 immunofluorescence, and normalization of β-tubulin expression levels. Unexpectedly, these OP-mediated protective effects were associated with increased superoxide and malondialdehyde generation and PARP cleavage.

DISCUSSION

OP protects HepG2 cells against PQ-induced necrosis by suppressing Casp-3 cleavage while concomitantly acting as a pro-oxidant agent. This paradoxical mechanism of action of OP requires further investigation.

Tissue apoptosis in mice infected with Leptospira interrogans serovar Icterohaemorrhagiae

BACKGROUND

This investigation aimed to evaluate the occurrence of some apoptotic features induced by Leptospira interrogans serovar Icterohaemorrhagiae infection in young BALB/c mice during 2, 4, 7, 10, 14 and 21 days post-infection (dpi).

METHODS

The animals were euthanized and lung, liver and kidneys were harvested to histopathology analysis and immunohistochemistry to caspase-3 antigen detection was performed.

RESULTS

Chromatin condensation in kidney and liver tissues, but not in lung tissue, was observed. Caspase-3 reactive cells, mainly characterized as renal epithelial cells, were detected in the days 14 and 21 at high levels when compared to days 2, 4 and 7 (p = 0.025; p < 0.05). Lung sections revealed caspase-3 labeled alveolar cells in 10 and 14 days post-infection was higher than observed at 7 days (p = 0.0497; p < 0.05). Liver sections demonstrated reactive cells at a highest level at 14 and 21 days post-infection when comparison to 2, 4, 7 and 10 days (p = 0.0069; p < 0.05).

CONCLUSIONS

Our results suggest that infection of L. interrogans induce in kidney, liver and lung an activation of apoptosis mediated by caspase-3 dependent pathway in later phases of infectious process.

Redox-sensitive glycogen synthase kinase 3β-directed control of mitochondrial permeability transition: rheostatic regulation of acute kidney injury

Mitochondrial dysfunction plays a pivotal role in necroapoptotic cell death and in the development of acute kidney injury (AKI). Evidence suggests that glycogen synthase kinase (GSK) 3β resides at the nexus of multiple signaling pathways implicated in the regulation of mitochondrial permeability transition (MPT). In cultured renal tubular epithelial cells, a discrete pool of GSK3β was detected in mitochondria. Coimmunoprecipitation assay confirmed that GSK3β physically interacts with cyclophilin F and voltage-dependent anion channel (VDAC), key MPT regulators that possess multiple GSK3β phosphorylation consensus motifs, suggesting that GSK3β has a direct control of MPT. Upon a strong burst of reactive oxygen species elicited by the pro-oxidant herbicide paraquat, the activity of the redox-sensitive GSK3β was drastically enhanced. This was accompanied by augmented phosphorylation of cyclophilin F and VDAC, associated with MPT and cell death. Inhibition of GSK3β by either the selective inhibitor 4-Benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8) or forced expression of a kinase-dead mutant obliterated paraquat-induced phosphorylation of cyclophilin F and VDAC, prevented MPT, and improved cellular viability. Conversely, ectopic expression of a constitutively active GSK3β amplified the effect of paraquat on cyclophilin F and VDAC phosphorylation and sensitized cells to paraquat-induced MPT and death. In vivo, paraquat injection elicited marked oxidant stress in the kidney and resulted in acute kidney dysfunction and massive tubular apoptosis and necrosis. Consistent with in vitro findings, the activity of GSK3β was augmented in the kidney after paraquat injury, associated with increased phosphorylation of cyclophilin F and VDAC and sensitized MPT. TDZD-8 blocked GSK3β activity in the kidney, intercepted cyclophilin F and VDAC phosphorylation, prevented MPT, attenuated tubular cell death, and ameliorated paraquat-induced AKI. Our data suggest that the redox-sensitive GSK3β regulates renal tubular injury in AKI by controlling the activity of MPT regulators.

Multimodal in vivo imaging and blood monitoring of intrinsic and extrinsic apoptosis

Noninvasive detection and in vivo imaging of apoptosis plays a critical role in the development of therapeutics in many different fields including cancer. We have developed an apoptosis biosensor by fusing green fluorescent protein (GFP) to the N-terminus of the naturally secreted Gaussia luciferase separated by a caspase-3 cleavage peptide consisting of aspartic acid (D), glutamic acid (E), valine (V), and aspartic acid (D) or DEVD. We showed that this fusion is retained in the cytoplasm of cells in an inactive form. Upon apoptosis, the DEVD peptide is cleaved in response to caspase-3 activation, freeing ssGluc, which can now enter the secretory pathway where it is folded properly and is released from the cells and can be detected in the conditioned medium in culture or in blood of live animals ex vivo over time. Because Gluc is secreted from cells via conventional pathway through the endoplasmic reticulum (ER), Golgi and vesicles, we showed that the presence of Gluc in these compartments in response to apoptosis can be visualized in vivo using bioluminescence imaging. This reporter provides a valuable tool for imaging and real-time monitoring of apoptosis and is compatible with high-throughput functional screening application in cultured cells and animal models.

Inflammation exacerbates seizure-induced injury in the immature brain

We examined the hypothesis that the introduction of an inflammatory agent would augment status epilepticus (SE)-induced neuronal injury in the developing rat brain in the absence of an increase in body temperature. Postnatal day 7 (P7) and P14 rat pups were injected with an exogenous provocative agent of inflammation, lipopolysaccharide (LPS), 2 h prior to limbic SE induced by either lithium-pilocarpine (LiPC) or kainic acid. Core temperature was recorded during the SE and neuronal injury was assessed 24 h later using profile cell counts in defined areas of the hippocampus. While LPS by itself did not produce any discernible cell injury at either age, it exacerbated hippocampal damage induced by seizures. In the LiPC model, this effect was highly selective for the CA1 subfield, and there was no concomitant rise in body temperature. Our findings show that inflammation increases the vulnerability of immature hippocampus to seizure-induced neuronal injury and suggest that inflammation might be an important factor aggravating the long-term outcomes of seizures occurring early in life.

Immunology of Apoptosis and Necrosis

A complex of reactions regulating the number of cells in organs and tissues under normal and pathologic conditions is one of the most important systems of multicellular organisms. In this system, which controls both cell proliferation and clearance, clearance has been given special attention during the last three decades. Some stages of the clearance are known (the choice of "unwanted" cells, their destruction not affecting the surrounding tissue, and, finally, removal of the corpses), and undeniable progress has been achieved in the understanding of the second stage mechanisms, whereas mechanisms of elimination per se of cells or their fragments still continue to be terra incognita. The clearance of such cells is mainly determined by different components of natural and adaptive immunity: phagocytes, complement, opsonins, antigen-presenting cells, etc. Recently specific "danger signals", such as hydrolases, DNA, heat shock proteins, and other potential immunogens released by cells during their elimination have been discovered. Entering the extracellular space, these signals induce inflammation and injury of the surrounding tissues, i.e., autoimmune reactions. Heat shock proteins, in addition to chaperon activity, act as signaling, costimulating, and antigen-carrying molecules in the interactions of dying cells and the immune system.