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Jake Jacobson

Publications and source records attributed to Jake Jacobson.

5 recordsLinked to original sources
PubMed2003

Firefly luciferin-activated rose bengal: in vitro photodynamic therapy by intracellular chemiluminescence in transgenic NIH 3T3 cells.

Photodynamic therapy (PDT) of cancer (1, 2) is a well-established treatment modality that uses light excitation of a photosensitive substance to produce oxygen-related cytotoxic intermediates, such as singlet oxygen or free radicals (3, 4). Although PDT is advantageous over other forms of cancer treatments because of its limited side effects, its main disadvantage is the poor accessibility of light to more deeply lying malignancies. External light sources such as lasers or lamps can be applied either noninvasively to reach tumors that lie well within the penetration depth of the light or in a minimally invasive fashion (interstitial treatments) in which optical fibers are placed intratumorally through needles. Even with the second approach, light distribution over the tumor is not homogeneous and nonidentified metastatic disease is left untreated. CL, the chemical production of light, is exemplified by firefly light emission mediated by the enzymatic (luciferase + ATP) oxidation of D-luciferin to oxyluciferin (5). This mobile light source is a targetable alternative to external sources of illumination. Here we show the in vitro photodynamic effect of rose bengal activated by intracellular generation of light, in luciferase-transfected NIH 3T3 murine fibroblasts.

3T3 Cells↗
PubMed2002

Mitochondrial oxidative stress and cell death in astrocytes--requirement for stored Ca2+ and sustained opening of the permeability transition pore.

The role of oxidative stress is established in a range of pathologies. As mitochondria are a major source of reactive oxygen species (ROS), we have developed a model in which an intramitochondrial photosensitising agent is used to explore the consequences of mitochondrial ROS generation for mitochondrial function and cell fate in primary cells. We have found that, in astrocytes, the interplay between mitochondrial ROS and ER sequestered Ca2+ increased the frequency of transient mitochondrial depolarisations and caused mitochondrial Ca2+ loading from ER stores. The depolarisations were attributable to opening of the mitochondrial permeability transition pore (mPTP). Initially, transient events were seen in individual mitochondria, but ultimately, the mitochondrial potential (Deltapsi(m)) collapsed completely and irreversibly in the whole population. Both ROS and ER Ca2+ were required to initiate these events, but neither alone was sufficient. Remarkably, the transient events alone appeared innocuous, and caused no increase in either apoptotic or necrotic cell death. By contrast, progression to complete collapse of Deltapsi(m) caused necrotic cell death. Thus increased mitochondrial ROS generation initiates a destructive cycle involving Ca2+ release from stores and mitochondrial Ca2+-loading, which further increases ROS production. The amplification of oxidative stress and Ca2+ loading culminates in opening of the mPTP and necrotic cell death in primary brain cells.

Animals↗
PubMed2002

Intracellular distribution of the fluorescent dye nonyl acridine orange responds to the mitochondrial membrane potential: implications for assays of cardiolipin and mitochondrial mass.

Cardiolipin, a polyunsaturated acidic phospholipid, is found exclusively in bacterial and mitochondrial membranes where it is intimately associated with the enzyme complexes of the respiratory chain. Cardiolipin structure and concentration are central to the function of these enzyme complexes and damage to the phospholipid may have consequences for mitochondrial function. The fluorescent dye, 10 nonyl acridine orange (NAO), has been shown to bind cardiolipin in vitro and is frequently used as a stain in living cells to assay cardiolipin content. Additionally, NAO staining has been used to measure the mitochondrial content of cells as dye binding to mitochondria is reportedly independent of the membrane potential. We used confocal microscopy to examine the properties of NAO in cortical astrocytes, neonatal cardiomyocytes and in isolated brain mitochondria. We show that NAO, a lipophilic cation, stained mitochondria selectively. However, the accumulation of the dye was clearly dependent upon the mitochondrial membrane potential and depolarisation of mitochondria induced a redistribution of dye. Moreover, depolarisation of mitochondria prior to NAO staining also resulted in a reduced NAO signal. These observations demonstrate that loading and retention of NAO is dependant upon membrane potential, and that the dye cannot be used as an assay of either cardiolipin or mitochondrial mass in living cells.

Acridine Orange↗
PubMedDate not supplied

Interplay between mitochondria and cellular calcium signalling.

Mitochondria are increasingly ascribed central roles in vital cell signalling cascades. These organelles are now recognised as initiators and transducers of a range of cell signals, including those central to activation and amplification of apoptotic cell death. Moreover, as the main source of cellular ATP, mitochondria must be responsive to fluctuating energy demands of the cell. As local and global fluctuations in calcium concentration are ubiquitous in eukaryotic cells and are the common factor in a dizzying array of intra- and inter-cellular signalling cascades, the relationships between mitochondrial function and calcium transients is currently a subject of intense scrutiny. It is clear that mitochondria not only act as local calcium buffers, thus shaping spatiotemporal aspects of cytosolic calcium signals, but that they also respond to calcium uptake by upregulating the tricarboxylic acid cycle, thus reacting metabolically to local signalling. In this chapter we review current knowledge of mechanisms of mitochondrial calcium uptake and release and discuss the consequences of mitochondrial calcium handling for cell function, particularly in conjunction with mitochondrial oxidative stress.

Calcium Signaling↗