Modulation of heat-induced cell death in PC-3 prostate cancer cells by the antioxidant inhibitor diethyldithiocarbamate

Context-dependent activation of STING-interferon signaling by CD11b agonists enhances anti-tumor immunity

Chronic activation of inflammatory pathways and suppressed interferon are hallmarks of immunosuppressive tumors. Previous studies have shown that CD11b integrin agonists could enhance anti-tumor immunity through myeloid reprograming, but the underlying mechanisms remain unclear. Herein we find that CD11b agonists alter tumor-associated macrophage (TAM) phenotypes by repressing NF-κB signaling and activating interferon gene expression simultaneously. Repression of NF-κB signaling involves degradation of p65 protein and is context independent. In contrast, CD11b agonism induces STING/STAT1 pathway-mediated interferon gene expression through FAK-mediated mitochondrial dysfunction, with the magnitude of induction dependent on the tumor microenvironment and amplified by cytotoxic therapies. Using tissues from phase I clinical studies, we demonstrate that GB1275 treatment activates STING and STAT1 signaling in TAMs in human tumors. These findings suggest potential mechanism-based therapeutic strategies for CD11b agonists and identify patient populations more likely to benefit.

Oxidative Stress and Inflammation Caused by Cisplatin Ototoxicity

Hearing loss is a significant health problem that can result from a variety of exogenous insults that generate oxidative stress and inflammation. This can produce cellular damage and impairment of hearing. Radiation damage, ageing, damage produced by cochlear implantation, acoustic trauma and ototoxic drug exposure can all generate reactive oxygen species in the inner ear with loss of sensory cells and hearing loss. Cisplatin ototoxicity is one of the major causes of hearing loss in children and adults. This review will address cisplatin ototoxicity. It includes discussion of the mechanisms associated with cisplatin-induced hearing loss including uptake pathways for cisplatin entry, oxidative stress due to overpowering antioxidant defense mechanisms, and the recently described toxic pathways that are activated by cisplatin, including necroptosis and ferroptosis. The cochlea contains G-protein coupled receptors that can be activated to provide protection. These include adenosine A1 receptors, cannabinoid 2 receptors (CB2) and the Sphingosine 1-Phosphate Receptor 2 (S1PR2). A variety of heat shock proteins (HSPs) can be up-regulated in the cochlea. The use of exosomes offers a novel method of delivery of HSPs to provide protection. A reversible MET channel blocker that can be administered orally may block cisplatin uptake into the cochlear cells. Several protective agents in preclinical studies have been shown to not interfere with cisplatin efficacy. Statins have shown efficacy in reducing cisplatin ototoxicity without compromising patient response to treatment. Additional clinical trials could provide exciting findings in the prevention of cisplatin ototoxicity.

Impacts of in vitro thermal stress on ovine epididymal spermatozoa and the protective effect of β-mercaptoethanol as an antioxidant

Most aspects of reproductive function including spermatogenesis, oocyte growth and maturation, early embryonic development, fetal and placental growth, and lactation can be affected by thermal stress. Furthermore, it has been shown that oxidative stress involves in the pathology of thermal stress. Therefore, the aim of this study was to investigate the impacts of thermal stress on the ovine mature epididymal spermatozoa extracted from testes of slaughtered rams in the presence or absence of an antioxidant. Epididymal spermatozoa were incubated at scrotal (32.00 ˚C), normal body (39.00 ˚C), and hyperthermic temperatures (41.00 ˚C) for 4 hr in the presence or absence of 1 mmol L^-1 β-mercaptoethanol. The results demonstrated the high sensitivity of ram epididymal spermatozoa to the hyperthermic temperature at in vitro conditions. In comparison with scrotal temperature, quality parameters of spermatozoa were negatively affected by increase in temperature, as such in the spermatozoa incubated at hyperthermic temperature significant decrease was observed in the viability, DNA integrity and in the majority of motility parameters. Moreover, concentration of lipid peroxidation by-products, thiobarbituric acid reactive substances, were significantly increased. The findings showed that using antioxidant during incubation period had significant protective effect on the viability and motility of incubated spermatozoa not only at the hyperthermic temperature, but also at the scrotal and normal body temperatures. In conclusion the ovine epididymal spermatozoa were sensitive to in vitro thermal stress and it seems that this sensitivity was partly related to the oxidative stress.

Association of elevated reactive oxygen species and hyperthermia induced radiosensitivity in cancer stem-like cells

Cancer stem-like cells (CSCs) are the principal causes of tumor radio-resistance, dormancy and recurrence after radiotherapy. Clinical trials show hyperthermia (HT) might be a potent radiation sensitizer. In this study, CSCs were found to be more susceptible to radiation when combined with HT treatment. Treated cells showed significantly reduced self-renewal, cell survival and proliferation in vitro, as well as significant reduced tumor formation in vivo. Further study demonstrated that the radiosensitization effect was associated with increased intracellular reactive oxygen species (ROS) level in CSCs, confirmed by modifying redox status in CSCs bidirectionally. Pharmacologic depletion of glutathione by buthionine sulphoximine mimicked HT induced radiosensitivity in CSCs. Antioxidant N-acetylcysteine could efficiently rescue HT induced radiosensitivity in CSCs. To our knowledge, this may be the first report suggesting the association between elevated intracellular ROS level and HT induced radiosensitization in human breast CSCs and pancreatic CSCs, which might provide new strategy for improving CSCs radiosensitivity.

Determining the critical effective temperature and heat dispersal pattern in monopolar radiofrequency ablation using temperature-time integration

The radiofrequency ablation (RFA) lesion size is posited to be disproportionate to the total delivered energy, and temperature-time integration (TTI) may have a more critical effect on lesion size. The present study aimed to evaluate this hypothesis by determining the temperature threshold and temperature distribution over tissues during the RFA lesioning process. Using an ex vivo chicken tissue model and an in vivo rabbit model with RFA applied for 2 min under various target temperature settings, the resultant lesions were evaluated histologically using Masson's trichrome stain. The temperature distribution over the tissue during the RFA lesioning process was also determined using a VT02 Visual IR Thermometer. It was revealed that the thermal injury threshold for RFA in the chicken tissues was ~65°C, but that it ranged from 55–65°C in mammals. Using infra-red thermal imaging, the temperature gradient (from the center to the periphery) during the RFA lesioning process demonstrated a uniform heat diffusion pattern. This data supports the proposed hypothesis that TTI is a critical parameter in determining RFA lesion size and can be applied clinically using the following equation: [Target temperature − 55 (°C)] × time (sec) is proportional to RFA lesion size.

Reactive oxygen species, heat stress and oxidative-induced mitochondrial damage. A review

In recent years there has been enormous interest in researching oxidative stress. Reactive oxygen species (ROS) are derived from the metabolism of oxygen as by-products of cell respiration, and are continuously produced in all aerobic organisms. Oxidative stress occurs as a consequence of an imbalance between ROS production and the available antioxidant defence against them. Nowadays, a variety of diseases and degenerative processes such as cancer, Alzheimer's and autoimmune diseases are mediated by oxidative stress. Heat stress was suggested to be an environmental factor responsible for stimulating ROS production because of similarities in responses observed following heat stress compared with that occurring following exposure to oxidative stress. This manuscript describes the main mitochondrial sources of ROS and the antioxidant defences involved to prevent oxidative damage in all the mitochondrial compartments. It also deals with discussions concerning the cytotoxic effect of heat stress, mitochondrial heat-induced alterations, as well as heat shock protein (HSP) expression as a defence mechanism.

Hyperthermia Induces Apoptosis of 786-O Cells through Suppressing Ku80 Expression

Hyperthermia as an anticancer method has been paid increasing attention in recent years. Several studies have shown that hyperthermia can kill tumor cells by inducing apoptosis. However, the underlying molecular mechanisms of hyperthermia-induced apoptosis are largely unknown. To investigate the effects and molecular mechanism of hyperthermia on the apoptosis in renal carcinoma 786-O cells, we firstly examined apoptosis and Ku expression in 786-O cell line treated with heat exposure (42°C for 0-4 h). The results showed that hyperthermia induced apoptosis of 786-O cells, and suppressed significantly Ku80 expression, but not Ku70 expression. Next, we knock-down Ku80 in 786-O cells, generating stable cell line 786-O-shKu80, and detected apoptosis, cell survival and cell cycle distribution. Our data showed higher apoptotic rate and lower surviving fraction in the stable cell line 786-O-shKu80 compared with those in control cells, exposed to the same heat stress (42°C for 0-4 h). Moreover, the results also showed suppression of Ku80 led to G2/M phase arrest in the stable cell line 786-O-shKu80 following heat treatment. Together, these findings indicate that Ku80 may play an important role in hyperthermia-induced apoptosis and heat-sensitivity of renal carcinoma cells through influencing the cell cycle distribution.

Increasing Superoxide Production and the Labile Iron Pool in Tumor Cells may Sensitize Them to Extracellular Ascorbate

Low millimolar concentrations of ascorbate are capable of inflicting lethal damage on a high proportion of cancer cells lines, yet leave non-transformed cell lines unscathed. Extracellular generation of hydrogen peroxide, reflecting reduction of molecular oxygen by ascorbate, has been shown to mediate this effect. Although some cancer cell lines express low catalase activity, this cannot fully explain the selective sensitivity of cancer cells to hydrogen peroxide. Ranzato and colleagues have presented evidence for a plausible new explanation of this sensitivity - a high proportion of cancers, via NADPH oxidase complexes or dysfunctional mitochondria, produce elevated amounts of superoxide. This superoxide, via a transition metal-catalyzed transfer of an electron to the hydrogen peroxide produced by ascorbate, can generate deadly hydroxyl radical (Haber-Weiss reaction). It thus can be predicted that concurrent measures which somewhat selectively boost superoxide production in cancers will enhance their sensitivity to i.v. ascorbate therapy. One way to achieve this is to increase the provision of substrate to cancer mitochondria. Measures which inhibit the constitutive hypoxia-inducible factor-1 (HIF-1) activity in cancers (such as salsalate and mTORC1 inhibitors, or an improvement of tumor oxygenation), or that inhibit the HIF-1-inducible pyruvate dehydrogenase kinase (such as dichloroacetate), can be expected to increase pyruvate oxidation. A ketogenic diet should provide more lipid substrate for tumor mitochondria. The cancer-killing activity of 42°C hyperthermia is to some degree contingent on an increase in oxidative stress, likely of mitochondrial origin; reports that hydrogen peroxide synergizes with hyperthermia in killing cancer cells suggest that hyperthermia and i.v. ascorbate could potentiate each other's efficacy. A concurrent enhancement of tumor oxygenation might improve results by decreasing HIF-1 activity while increasing the interaction of ascorbic acid with oxygen. An increased pool of labile iron in cancer cells may contribute to the selective susceptibility of many cancers to i.v. ascorbate; antagonism of NF-kappaB activity with salicylate, and intravenous iron administration, could be employed to further elevate free iron in cancers.

Proteomic analysis of protein expression profiles during hyperthermia-induced apoptosis in Tca8113 cells

The aim of the present study was to explore protein expression profiles during cancer cell apoptosis induced by hyperthermia. A hyperthermia-induced apoptosis model was established using a Tca8113 cell line derived from a human tongue squamous cell carcinoma, which underwent fluorescent differential display two-dimensional (2D) gel electrophoresis at 2, 6, 8, 12 and 24 h following the induction of hyperthermia. Proteins were identified by mass spectrometry analysis. Expression changes in the proteins were detected by western blot analysis. A total of 107 proteins were detected that exhibited different expression levels in the hyperthermia-treated cells compared with the controls, and 57 of these proteins were identified. Expression changes in the representative proteins were further verified by western blot analysis. These 57 proteins were identified according to the following functional groups: energy metabolism-related enzymes, cytoskeleton-related proteins, chaperones, transcription factors, protein synthesis-related proteins and cell division- and proliferation-related proteins. These groups included 44 upregulated and 13 downregulated proteins. Among the 44 upregulated proteins, 27 were upregulated continuously, eight were upregulated at an early time-point and nine were upregulated at a middle to late time-point. Among the 13 downregulated proteins, five were downregulated continuously, six were downregulated at an early time-point and two were downregulated at a middle to late time-point. These results indicate that hyperthermia-induced Tca8113 cell apoptosis is controlled by multiple factors, which include time and regulatory proteins.

Gold nanoparticles grown on ionic liquid-functionalized single-walled carbon nanotubes: new materials for photothermal therapy

Gold nanoparticles were grown on single-walled carbon nanotubes (SWNTs) coated with a thiol-functionalized ionic liquid resulting in the formation of core-shell structures referred to as SWNT-IL-Au nanohybrid materials. The nanohybrid materials were characterized by high-resolution transmission electron microscopy (HR-TEM), Raman-, and UV/Vis absorption spectroscopy. The nanohybrid materials were found to enter lysosomes in HeLa cells and show negligible cytotoxicity. Interestingly, they have an enhanced NIR absorption that is effectively transferred into heat to cause localized hyperthermia, resulting in rapid cell death; overall, the material appears to have excellent properties for photothermal therapeutic applications.

Heat shock but not cold shock leads to disturbed intracellular zinc homeostasis

The heat shock response is a highly conserved process essential for surviving environmental stress, including extremes of temperature. To investigate whether heat shock has an impact on intracellular Zn(2+) homeostasis, cells were subjected to heat shock, and subsequently the intracellular free zinc concentration was investigated. Sublethal heat shock induced a temperature-dependent and transient intracellular Zn(2+) release that was repeatable after 24 h. The free zinc was localized in round-shaped nuclear bodies identified as nucleoli. Metallothionein, the main cellular zinc storing protein, was found to be not functionally essential for this heat-shock-induced effect. No significant oxidative stress within the cells was detected after heat shock. Cold shock and subsequent rewarming did not result in disturbed intracellular zinc homeostasis. These results show that heat shock and cold shock differ with respect to intracellular Zn(2+) release. A role for zinc as signaling ion during fever is conceivable.

Induction of hsp70, alterations in oxidative stress markers and apoptosis against dichlorvos exposure in transgenic Drosophila melanogaster: Modulation by reactive oxygen species

We examined a hypothesis that reactive oxygen species (ROS) generated by organophosphate compound dichlorvos modulates Hsp70 expression and anti-oxidant defense enzymes and acts as a signaling molecule for apoptosis in the exposed organism. Dichlorvos (0.015-15.0 ppb) without or with inhibitors of Hsp70, superoxide dismutase (SOD) and catalase (CAT) were fed to the third instar larvae of Drosophila melanogaster transgenic for hsp70 (hsp70-lacZ) Bg(9) to examine Hsp70 expression, oxidative stress and apoptotic markers. A concentration- and time-dependent significant increase in ROS generation accompanied by a significant upregulation of Hsp70 preceded changes in antioxidant defense enzyme activities and contents of glutathione, malondialdehyde and protein carbonyl in the treated organisms. An inhibitory effect on SOD and CAT activities significantly upregulated ROS generation and Hsp70 expression in the exposed organism while inhibition of Hsp70 significantly affected oxidative stress markers induced by the test chemical. A comparison made among ROS generation, Hsp70 expression and apoptotic markers showed that ROS generation is positively correlated with Hsp70 expression and apoptotic cell death end points indicating involvement of ROS in the overall adversity caused by the test chemical to the organism. The study suggests that (a) Hsp70 and anti-oxidant enzymes work together for cellular defense against xenobiotic hazard in D. melanogaster and (b) free radicals may modulate Hsp70 expression and apoptosis in the exposed organism.

Cellular and molecular mechanism and application of hyperthermia for tumor therapy

Hyperthermia is effective in the treatment of neoplasm, but its mechanism remains unclear for a long time. In recent years, great advances were achieved on its mechanism. In vitro and in vivo studies show that heat-induced apoptosis plays a dominant role in mild and moderate hyperthermia while necrosis in serious one. Heat induces apoptosis through mitochondria or/and death receptor pathways, and oxidative stress, intracellular Ca²⁺ increase and some molecules such as p53 and Bax play important roles in this process. Based on this mechanism, new therapies have been investigated and developed, including hyperthermia combined with gene therapy, calcium- and oxidative stress-targeted therapy, or decreasing extracellular pH value, which may remarkably enhance the effect of hyperthermia.

Cellular mechanisms of neuronal damage from hyperthermia

Hyperthermia can cause brain damage and also exacerbate the brain damage produced by stroke and amphetamines. The developing brain is especially sensitive to hyperthermia. The severity of, and mechanisms underlying, hyperthermia-induced neuronal death depend on both temperature and duration of exposure. Severe hyperthermia can produce necrotic neuronal death. For a window of less severe heat stresses, cultured neurons exhibit a delayed death with apoptotic characteristics including cytochrome c release and caspase activation. Little is known about mechanisms of hyperthermia-induced damage upstream of these late apoptotic effects. This chapter considers several possible upstream mechanisms, drawing on both in vivo and in vitro studies of the nervous system and other tissues. Hyperthermia-induced damage in some non-neuronal cells includes endoplasmic reticular stress due to denaturing of nascent polypeptide chains, as well as nuclear and cytoskeletal damage. Evidence is presented that hyperthermia produces mitochondrial damage, including depolarization, in cultured mammalian neurons.

Heat shock inhibits both aminoglycoside- and cisplatin-induced sensory hair cell death

Human hearing and balance impairments are often attributable to the death of sensory hair cells in the inner ear. These cells are hypersensitive to death induced by noise exposure, aging, and some therapeutic drugs. Two major classes of ototoxic drugs are the aminoglycoside antibiotics and the antineoplastic agent cisplatin. Exposure to these drugs leads to hair cell death that is mediated by the activation of specific apoptotic proteins, including caspases. The induction of heat shock proteins (HSPs) in response to cellular stress is a ubiquitous and highly conserved response that can significantly inhibit apoptosis in some systems by inhibiting apoptotic proteins. Induction of HSPs occurs in hair cells in response to a variety of stimuli. Given that HSPs can directly inhibit apoptosis, we hypothesized that heat shock may inhibit apoptosis in hair cells exposed to ototoxic drugs. To test this hypothesis, we developed a method for inducing HSP expression in the adult mouse utricle in vitro. In vitro heat shock reliably produces a robust up-regulation of HSP-70 mRNA and protein, as well as more modest up-regulation of HSP-90 and HSP-27. The heat shock does not result in death of hair cells. Heat shock has a significant protective effect against both aminoglycoside- and cisplatin-induced hair cell death in the utricle preparation in vitro. These data indicate that heat shock can inhibit ototoxic drug-induced hair cell death, and that the utricle preparation can be used to examine the molecular mechanism(s) underlying this protective effect.

Nuclear clusterin accumulation during heat shock response: implications for cell survival and thermo-tolerance induction in immortalized and prostate cancer cells

Clusterin (CLU), whose role is still debated, is differentially regulated in several patho-physiological processes and invariably induced during apoptosis. In heat shock response, CLU is considered a stress-inducible, pro-survival/cyto-protective factor via an HSE element present in his promoter. In both human prostate PNT1A and PC-3 epithelial cells we found that apoptotic stimuli induced nuclear localization of CLU (nCLU), and that overexpression of nCLU is pro-apoptotic. We show here that CLU time-course accumulation kinetic is different from that of HSP70 in these cells, thus other factor(s) might mediate HSF-1 activation and CLU expression. Sub-lethal heat shock inhibited the secretion of CLU (sCLU), leading to increased cytoplasm accumulation of CLU (cCLU) in association to cell survival. At difference, lethal heat stress caused massive accumulation of pro-apoptotic nCLU in cells dying by caspase-3-dependent apoptosis. Double heat stress (sub-lethal heat shock followed by recovery and lethal stress) induced HSP70 and thermo-tolerance in PNT1A cells, but not in PC-3 cells. In PNT1A cells, CLU secretion was inhibited and cCLU was accumulated, suggesting that cCLU might be pro-survival, while in PC-3 cells accumulation of nCLU was concomitant to caspase-3 induction and PARP activation instead. Thus, CLU expression/sub-cellular localization is strictly related to cell fate. In particular, nCLU and physiological levels of HSP70 affected cell survival in an antagonistic fashion. Prevalence of heat-induced nCLU, not allowing PC-3 cells to cope with heat shock, could be the rational explaining why malignant cells are more sensitive to heat when delivered by minimally invasive procedures for ablation of localized prostate cancer.

Regulation of the multidrug resistance transporter P-glycoprotein in multicellular prostate tumor spheroids by hyperthermia and reactive oxygen species

Hyperthermia is an important component of many cancer treatment protocols. In our study the regulation of the multidrug resistance (MDR) transporter P-glycoprotein by hyperthermia was studied in multicellular prostate tumor spheroids. Hyperthermia treatment of small (50-100 microm) tumor spheroids significantly increased P-glycoprotein and mdr-1 mRNA expression with a maximum effect at 42 degrees C, whereas only moderate elevation of P-glycoprotein was found in large (350-450 microm) tumor spheroids. Hyperthermia caused an elevation of intracellular reactive oxygen species (ROS). Inhibition of ROS generation with NADPH-oxidase inhibitors diphenylen iodonium (DPI) and 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF) abolished P-glycoprotein expression but did not affect its transcript levels following heat treatment. This indicates that P-glycoprotein levels are controlled by regulating its translation rate or stability. Hyperthermia incubation resulted in a differential activation of p38 mitogen-activated protein kinase (MAPK), extracellular regulated kinase 1,2 (ERK1,2), and c-jun N-terminal kinase (JNK) immediately, 4 hr and 24 hr after treatment. Furthermore, upregulation of hypoxia-inducible factor 1alpha (HIF-1alpha) was observed. Elevation of HIF-1alpha and P-glycoprotein expression following hyperthermia treatment were abolished upon coadministration of the p38 inhibitor SB203580. In contrast the JNK inhibitor SP600125 and the ERK1,2 inhibitor UO126 resulted in increase of HIF-1alpha and P-glycoprotein in the control as well as the hyperthermia-treated samples, indicating negative regulation of intrinsic HIF-1alpha and P-glycoprotein expression by ERK1,2 and JNK signaling cascades. In summary our data demonstrate that hyperthermia-induced upregulation of P-glycoprotein and HIF-1alpha is mediated by activation of p38, whereas ERK1,2 and JNK are involved in repression of P-glycoprotein and HIF-1alpha under control conditions.

Selective hyperthermia using magnetoliposomes to target cervical lymph node metastasis in a rabbit tongue tumor model

The effect of hyperthermia on cervical lymph node metastasis of VX7 tongue cancer in female Japanese white rabbits was investigated. Magnetoliposomes (MLs) with a neutral surface charge and a size of 94.1 nm were used as heating mediators. MLs were injected into the tongue 20 days after tumor transplantation, and we examined whether they reached the metastatic deep cervical lymph node. The highest magnetite concentration 24 h after ML injection was detected in the lymph node, followed by tongue, spleen, blood, and liver. Rabbits were separated into three groups: group I as the control; group II with ML injection alone; and group III with ML injection and hyperthermia 24 h after ML injection, generated by applying an alternating magnetic field (118 kHz, 384 Oe) to the neck region. The hyperthermic effect was evaluated in terms of the percentage of necrosis in proportion to the metastatic tumor and the apoptotic index (AI), defined as the ratio of TUNEL-positive cells. The temperature of lymph nodes in group III reached over 44 degrees C. The mean area of necrosis in group III was 58.0%, which was significantly higher than that in group I (19.6%) or group II (20.4%). The AI in group III was 22.9%, significantly higher than in group I (1.67%) or II (1.42%). The difference between group I and II was not statistically significant. Group III tumor sites around MLs showed necrosis or apoptosis-positive cells induced by hyperthermia. These results indicate that MLs injected into the tongue can target cervical lymph node metastases and accumulate there at concentrations sufficient to generate therapeutically effective temperatures.