Enhanced ability of plasma-activated lactated Ringer's solution to induce A549 cell injury

Comparing Redox and Intracellular Signalling Responses to Cold Plasma in Wound Healing and Cancer

Cold plasma (CP) is an ionised gas containing excited molecules and ions, radicals, and free electrons, and which emits electric fields and UV radiation. CP is potently antimicrobial, and can be applied safely to biological tissue, birthing the field of plasma medicine. Reactive oxygen and nitrogen species (RONS) produced by CP affect biological processes directly or indirectly via the modification of cellular lipids, proteins, DNA, and intracellular signalling pathways. CP can be applied at lower levels for oxidative eustress to activate cell proliferation, motility, migration, and antioxidant production in normal cells, mainly potentiated by the unfolded protein response, the nuclear factor-erythroid factor 2-related factor 2 (Nrf2)-activated antioxidant response element, and the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) pathway, which also activates nuclear factor-kappa B (NFκB). At higher CP exposures, inactivation, apoptosis, and autophagy of malignant cells can occur via the degradation of the PI3K/Akt and mitogen-activated protein kinase (MAPK)-dependent and -independent activation of the master tumour suppressor p53, leading to caspase-mediated cell death. These opposing responses validate a hormesis approach to plasma medicine. Clinical applications of CP are becoming increasingly realised in wound healing, while clinical effectiveness in tumours is currently coming to light. This review will outline advances in plasma medicine and compare the main redox and intracellular signalling responses to CP in wound healing and cancer.

Mechanism of non-thermal atmospheric plasma in anti-tumor: influencing intracellular RONS and regulating signaling pathways

Non-thermal atmospheric plasma (NTAP) has been proven to be an effective anti-tumor tool, with various biological effects such as inhibiting tumor proliferation, metastasis, and promoting tumor cell apoptosis. At present, the main conclusion is that ROS and RNS are the main effector components of NTAP, but the mechanisms of which still lack systematic summary. Therefore, in this review, we first summarized the mechanism by which NTAP directly or indirectly causes an increase in intracellular RONS concentration, and the multiple pathways dysregulation (i.e. NRF2, PI3K, MAPK, NF-κB) induced by intracellular RONS. Then, we generalized the relationship between NTAP induced pathways dysregulation and the various biological effects it brought. The summary of the anti-tumor mechanism of NTAP is helpful for its further research and clinical transformation.

Medical gas plasma technology: Roadmap on cancer treatment and immunotherapy

Despite continuous therapeutic progress, cancer remains an often fatal disease. In the early 2010s, first evidence in rodent models suggested promising antitumor action of gas plasma technology. Medical gas plasma is a partially ionized gas depositing multiple physico-chemical effectors onto tissues, especially reactive oxygen and nitrogen species (ROS/RNS). Today, an evergrowing body of experimental evidence suggests multifaceted roles of medical gas plasma-derived therapeutic ROS/RNS in targeting cancer alone or in combination with oncological treatment schemes such as ionizing radiation, chemotherapy, and immunotherapy. Intriguingly, gas plasma technology was recently unraveled to have an immunological dimension by inducing immunogenic cell death, which could ultimately promote existing cancer immunotherapies via in situ or autologous tumor vaccine schemes. Together with first clinical evidence reporting beneficial effects in cancer patients following gas plasma therapy, it is time to summarize the main concepts along with the chances and limitations of medical gas plasma onco-therapy from a biological, immunological, clinical, and technological point of view.

Current understanding of Plasma-activated solutions for potential cancer therapy

Cancer therapy consists of multidisciplinary treatment combining surgery, chemotherapy, radiotherapy, and immunotherapy. Despite the elucidation of cancer mechanisms by comprehensive genomic and epigenomic analyses and the development of molecular therapy, drug resistance and severe side effects have presented challenges to the long-awaited development of new therapies. With the rapid technological advances in the last decade, there are now reports concerning potential applications of non-equilibrium atmospheric pressure plasma (NEAPP) in cancer therapy. Two approaches have been tried: direct irradiation with NEAPP (direct plasma) and the administration of a liquid (e.g., culture medium, saline, Ringer's lactate) activated by NEAPP (plasma-activated solutions: PAS). Direct plasma is a unique treatment method in which various active species, charged ions, and photons are delivered to the affected area, but the direct plasma approach has physical limitations related to the device used, such as a limited depth of reach and limited irradiation area. PAS is a liquid that contains reactive oxygen species generated by PAS, and it has been confirmed to have antitumor activity that functions in the same manner as direct plasma. This review introduces recent studies of PAS and informs researchers about the potential of PAS for cancer therapy.Key Policy HighlightsPotential applications of plasma-activated solutions (PAS) in cancer therapy are described.Plasma-activated species generated in PAS, its effect on tumor cells, contribution to non-malignant immune cells, selectivity and safety are presented.The proposed anti-tumor mechanisms of PAS to date are described.Efficacy and safety evaluations of PAS have been studied in experimental animal models, but no human studies have been conducted.

Argon gas plasma-treated physiological solutions stimulate immunogenic cell death and eradicates immunosuppressive CD47 protein in lung carcinoma

Cold atmospheric plasma-treated liquids (PTLs) exhibit selective toxicity toward tumor cells and are provoked by a cocktail of reactive oxygen and nitrogen species in such liquids. Compared to the gaseous phase, these reactive species are more persistent in the aqueous phase. This indirect plasma treatment method has gradually gathered interest in the discipline of plasma medicine to treat cancer. PTL's motivated effect on immunosuppressive proteins and immunogenic cell death (ICD) in solid cancer cells is still not explored. In this study, we aimed to induce immunomodulation by plasma-treated Ringer's lactate (PT-RL) and phosphate-buffered saline (PT-PBS) solutions for cancer treatment. PTLs induced minimum cytotoxicity in normal lung cells and inhibited cancer cell growth. ICD is confirmed by the enhanced expression of damage-associated molecular patterns (DAMPs). We evidenced that PTLs induce intracellular nitrogen oxide species accumulation and elevate immunogenicity in cancer cells owing to the production of pro-inflammatory cytokines, DAMPs, and reduced immunosuppressive protein CD47 expression. In addition, PTLs influenced A549 cells to elevate the organelles (mitochondria and lysosomes) in macrophages. Taken together, we have developed a therapeutic approach to potentially facilitate the selection of a suitable candidate for direct clinical applications.

The Role of Autophagy and Apoptosis in the Combined Action of Plasma-Treated Saline, Doxorubicin, and Medroxyprogesterone Acetate on K562 Myeloid Leukaemia Cells

The anti-cancer properties of plasma-treated solutions (PTS) and their interaction with drugs are one of the most popular topics in modern plasma medicine. Our research involved comparing the effects of four physiological saline solutions (0.9% NaCl, Ringer’s solution, Hank’s Balanced Salt Solution, Hank’s Balanced Salt Solution with amino acids added in concentrations observed in the human blood) treated with cold atmospheric plasma and studying the combined cytotoxic effect of PTS with doxorubicin and medroxyprogesterone acetate (MPA). Analysis of the effect of the studied agents on the formation of radicals in the incubation medium, the vitality of K562 myeloid leukaemia cells, and the processes of autophagy and apoptosis in them revealed two key findings. The first is that when using PTS and doxorubicin-containing PTS, autophagy is the predominant process in cancer cells. The second is that combining PTS with MPA enhances apoptotic processes. It was hypothesised that while autophagy is stimulated by the accumulation of reactive oxygen species in the cell, apoptosis is stimulated through specific cell progesterone receptors.

Gas plasma-oxidized sodium chloride acts via hydrogen peroxide in a model of peritoneal carcinomatosis

Gas plasma technology generates reactive oxygen and nitrogen species (ROS/RNS), inducing lethal oxidative damage in tumor cells. The transfer of gas plasma-derived ROS/RNS into liquids has been proposed as an innovative anti-cancer strategy targeting peritoneal carcinomatosis (PC). However, the mechanism of action is under debate. To this end, we compared gas plasma-oxidized medical-grade sodium chloride (oxNaCl) with a concentration-matched control (cmc) of NaCl enriched with equivalent concentrations of H₂O₂ and NO₃^- in several cell lines and models of PC. Strikingly, oxNaCl and cmc performed equally well in oxidation and cytotoxic activity in tumor cells in two-dimensional cultures, three-dimensional (3D) tumor spheroids, vascularized 3D tumors grown on chicken-embryo chorioallantoic membranes, and a syngeneic PC mouse model in vivo. Given the importance of immunotherapies in oncology today, we focused on immunological consequences of the treatment. Again, to a similar extent, oxNaCl and cmc increased tumor cell immunogenicity and enhanced uptake by and maturation of peripheral blood monocyte-derived dendritic cells together with an inflammatory secretion profile. Furthermore, NanoString gene expression profiling revealed immune system processes and unfolded protein response-related pathways as being linked to the observed anti-tumor effects for both oxNaCl and cmc. In conclusion, gas plasma-generated oxNaCl and cmc showed equal therapeutic efficacy in our PC-related models. In light of the many promising anti-cancer studies of gas plasma-oxidized liquids and the convenient production of corresponding cmcs in large quantities as needed in clinics, our findings may spur research lines based on low-dose oxidants in peritoneal cancer therapy.

[Molecular Mechanisms Underlying Cellular Responses to the Loading of Non-thermal Atmospheric Pressure Plasma-activated Solutions]

Plasma medicine is a rapidly expanding new field of interdisciplinary research that combines physics, chemistry, biology, and medicine. Non-thermal atmospheric pressure plasma (NTAPP) has recently been applied to living cells and tissues, and has emerged as a novel technology for medical applications, such as wound healing, blood coagulation, and cancer treatment. NTAPP was found to affect cells indirectly through the treatment of cells with previously prepared medium irradiated by NTAPP, termed plasma-activated medium (PAM). The treatment of culture media with NTAPP results in the generation of a large amount of reactive oxygen species and reactive nitrogen species, and their derived species. We found that PAM triggered a spiral apoptotic cascade in the mitochondrial-nuclear network in A549 cancer cells. This process induced the depletion of total cellular NAD⁺ and elevations in intracellular calcium ion, ultimately leading to cell death. We also detected the production of hydroxyl radical and elevations in intracellular ferrous ions in PAM-treated cells. The elevations observed in ferrous ions may have been due to their release from the intracellular iron store, ferritin. However, difficulties are associated with applying PAM to the clinical phase because culture media cannot be used for medical treatments. The anti-tumor activity of plasma-activated Ringer's solution was significantly stronger than that of PAM. At the end, we herein demonstrated the advantages of the combined application of plasma-activated acetate Ringer's solution and hyperthermia, a heat treatment at 42℃, for A549 cancer cell death and elucidated the underlying mechanisms.

The Anticancer Efficacy of Plasma-Oxidized Saline (POS) in the Ehrlich Ascites Carcinoma Model In Vitro and In Vivo

Cold physical plasma, a partially ionized gas rich in reactive oxygen species (ROS), is receiving increasing interest as a novel anticancer agent via two modes. The first involves its application to cells and tissues directly, while the second uses physical plasma-derived ROS to oxidize liquids. Saline is a clinically accepted liquid, and here we explored the suitability of plasma-oxidized saline (POS) as anticancer agent technology in vitro and in vivo using the Ehrlich Ascites Carcinoma (EAC) model. EAC mainly grows as a suspension in the peritoneal cavity of mice, making this model ideally suited to test POS as a putative agent against peritoneal carcinomatosis frequently observed with colon, pancreas, and ovarium metastasis. Five POS injections led to a reduction of the tumor burden in vivo as well as in a decline of EAC cell growth and an arrest in metabolic activity ex vivo. The treatment was accompanied by a decreased antioxidant capacity of Ehrlich tumor cells and increased lipid oxidation in the ascites supernatants, while no other side effects were observed. Oxaliplatin and hydrogen peroxide were used as controls and mediated better and worse outcomes, respectively, with the former but not the latter inducing profound changes in the inflammatory milieu among 13 different cytokines investigated in ascites fluid. Modulation of inflammation in the POS group was modest but significant. These results promote POS as a promising candidate for targeting peritoneal carcinomatosis and malignant ascites and suggest EAC to be a suitable and convenient model for analyzing innovative POS approaches and combination therapies.

Non-thermal plasma-induced DMPO-OH yields hydrogen peroxide

Recent developments in electronics have enabled the medical applications of non-thermal plasma (NTP), which elicits reactive oxygen species (ROS) and reactive nitrogen species (RNS), such as hydroxyl radical (●OH), hydrogen peroxide (H2O2), singlet oxygen (1O2), superoxide (O2●-), ozone, and nitric oxide at near-physiological temperatures. In preclinical studies or human clinical trials, NTP promotes blood coagulation, eradication of bacterial, viral and biofilm-related infections, wound healing, and cancer cell death. To elucidate the solution-phase biological effects of NTP in the presence of biocompatible reducing agents, we employed electron paramagnetic resonance (EPR) spectroscopy to quantify ●OH using a spin-trapping probe, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO); 1O2 using a fluorescent probe; and O2●- and H2O2 using luminescent probes in the presence of thiols or tempol. NTP-induced ●OH was significantly scavenged by dithiothreitol (DTT), reduced glutathione (GSH), and oxidized glutathione (GSSG) in 2 or 5 mM DMPO. NTP-induced O2●- was significantly scavenged by 10 μM DTT and GSH, while 1O2 was not efficiently scavenged by these compounds. GSSG degraded H2O2 more effectively than GSH and DTT, suggesting that the disulfide bonds reacted with H2O2. In the presence of 1-50 mM DMPO, NTP-induced H2O2 quantities were unchanged. The inhibitory effect of tempol concentration (50 and 100 μM) on H2O2 production was observed in 1 and 10 mM DMPO, whereas it became ineffective in 50 mM DMPO. Furthermore, DMPO-OH did not interact with tempol. These results suggest that DMPO and tempol react competitively with O2●-. Further studies are warranted to elucidate the interaction between NTP-induced ROS and biomolecules.

Lysosomal nitric oxide determines transition from autophagy to ferroptosis after exposure to plasma-activated Ringer's lactate

Non-thermal plasma (NTP), an engineered technology to generate reactive species, induces ferroptosis and/or apoptosis specifically in various-type cancer cells. NTP-activated Ringer's lactate (PAL) is another modality for cancer therapy at preclinical stage. Here we found that PAL induces selective ferroptosis of malignant mesothelioma (MM) cells, where non-targeted metabolome screening identified upregulated citrulline-nitric oxide (^.NO) cycle as a PAL target. ^.NO probe detected biphasic peaks transiently at PAL exposure with time-dependent increase, which was responsible for inducible ^. NO synthase (iNOS) overexpression through NF-κB activation. ^.NO and lipid peroxidation occupied lysosomes as a major compartment with increased TFEB expression. Not only ferrostatin-1 but inhibitors for ^. NO and/or iNOS could suppress this ferroptosis. PAL-induced ferroptosis accompanied autophagic process in the early phase, as demonstrated by an increase in essential amino acids, LC3B-II, p62 and LAMP1, transforming into the later phase with boosted lipid peroxidation. Therefore, ^.NO-mediated lysosomal impairment is central in PAL-induced ferroptosis.

L-Dehydroascorbate efficiently degrades non-thermal plasma-induced hydrogen peroxide

Non-thermal plasma (NTP) devices generate reactive oxygen species (ROS) and reactive nitrogen species, such as singlet oxygen (¹O₂), superoxide (O₂^-), hydroxyl radical (^●OH), hydrogen peroxide (H₂O₂), ozone, and nitric oxide at near-physiological temperature. In preclinical studies, NTP promotes blood coagulation, wound healing with disinfection, and selective killing of cancer cells. Although these biological effects of NTP have been widely explored, the stoichiometric quantitation of ROS in the liquid phase has not been performed in the presence of biocompatible reducing agents, which may modify the final biological effects of NTP. Here, we utilized electron paramagnetic resonance spectroscopy to quantitate ^●OH, using a spin-trapping probe 5,5-dimethyl-1-pyrroline-N-oxide; ¹O₂, using a fluorescent probe; and O₂^- and H₂O₂, using luminescent probes, after NTP exposure in the presence of antioxidants. l-ascorbate (Asc) at 50 μM concentration (physiological concentration in serum) significantly scavenged ^●OH, whereas (-)-epigallocatechin gallate (EGCG) and α-tocopherol were also effective at performing scavenging activities at 250 μM concentrations. Asc significantly scavenged O₂^- and H₂O₂ at 100 μM. l-Dehydroascorbate (DHA), an oxidized form of Asc, degraded H₂O₂, whereas it did not quench ^●OH or O₂^-, which are sources of H₂O₂. Furthermore, EGCG efficiently scavenged NTP-induced ¹O₂, O₂^-, and H₂O₂ in Chelex-treated water. These results indicate that the redox cycling of Asc/DHA and metabolites of DHA are important to be considered when applying NTP to cells and tissues. Additionally, ROS-reducing compounds, such as EGCG, affect the outcome. Further studies are warranted to elucidate the interaction between ROS and biomolecules to promote the medical applications of NTP.

Hyperthermia synergistically enhances cancer cell death by plasma-activated acetated Ringer's solution

Applications of non-thermal plasma (NTP) discharges in medicine, particularly cancer therapy, have increased in recent years. The aim of the present study was to investigate the advantages of the combined application of NTP-irradiated acetated Ringer's solution (PAA) and hyperthermia, a heat treatment at 42 °C, on A549 cancer cell death and elucidate the underlying mechanisms. Cell death was enhanced more by the above combined treatment and was accompanied by increases in intracellular calcium ([Ca²⁺]i). The activation of transient receptor potential melastatin 2 (TRPM2) may enhance cell death because the addition of TRPM2 inhibitors and knockdown of TRPM2 significantly abrogated the above phenomena. TRPM2 is a temperature-sensitive, Ca²⁺-permeable, non-elective cation channel and hydrogen peroxide (H₂O₂) and ADP ribose are its main agonists. PAA functioned as a donor of reactive oxygen species, mainly H₂O₂, and a treatment with PAA under hyperthermia induced both mitochondrial and nuclear damage with DNA breaks. The activation of poly(ADP-ribose) polymerase-1 as the DNA repair mechanism induced TRPM2 activation because this enzyme accumulates ADP ribose. The sensitivity of fibroblasts as normal cells to PAA was less than that of A549 cells. These results suggest that hyperthermia synergistically induces the sensitivity of cancer cells to PAA.

Non-thermal plasma-activated lactate solution kills U251SP glioblastoma cells in an innate reductive manner with altered metabolism

Ringer's lactate solution irradiated by non-thermal plasma, comprised of radicals, electrons, and ions, is defined as plasma-activated lactate (PAL). PAL exhibited antitumor effects in glioblastoma U251SP cells, which we termed PAL-specific regulated cell death. In contrast to the oxidative stress condition typical of cells incubated in plasma-activated medium (PAM), U251SP cells treated with Ringer's lactate solution or PAL exhibited changes in intracellular metabolites that were reductive in the redox state, as measured by the ratio of oxidative/reductive glutathione concentrations. In the metabolomic profiles of PAL-treated cells, the generation of acetyl-CoA increased for lipid metabolism from alanine and asparagine. PAL thus induces regulated death of U251SP glioblastoma cells in more innate microenvironments than PAM.

Cold Atmospheric Plasma: A Powerful Tool for Modern Medicine

Cold atmospheric plasma use in clinical studies is mainly limited to the treatment of chronic wounds, but its application in a wide range of medical fields is now the goal of many analyses. It is therefore likely that its application spectrum will be expanded in the future. Cold atmospheric plasma has been shown to reduce microbial load without any known significant negative effects on healthy tissues, and this should enhance its possible application to any microbial infection site. It has also been shown to have anti-tumour effects. In addition, it acts proliferatively on stem cells and other cultivated cells, and the highly increased nitric oxide levels have a very important effect on this proliferation. Cold atmospheric plasma use may also have a beneficial effect on immunotherapy in cancer patients. Finally, it is possible that the use of plasma devices will not remain limited to surface structures, because current endeavours to develop sufficiently miniature microplasma devices could very likely lead to its application in subcutaneous and internal structures. This study summarises the available literature on cold plasma action mechanisms and analyses of its current in vivo and in vitro use, primarily in the fields of regenerative and dental medicine and oncology.

Plasma-activated Ringer's Lactate Solution Displays a Selective Cytotoxic Effect on Ovarian Cancer Cells

Epithelial Ovarian Cancer (EOC) is one of the leading causes of cancer-related deaths among women and is characterized by the diffusion of nodules or plaques from the ovary to the peritoneal surfaces. Conventional therapeutic options cannot eradicate the disease and show low efficacy against resistant tumor subclones. The treatment of liquids via cold atmospheric pressure plasma enables the production of plasma-activated liquids (PALs) containing reactive oxygen and nitrogen species (RONS) with selective anticancer activity. Thus, the delivery of RONS to cancer tissues by intraperitoneal washing with PALs might be an innovative strategy for the treatment of EOC. In this work, plasma-activated Ringer’s Lactate solution (PA-RL) was produced by exposing a liquid substrate to a multiwire plasma source. Subsequently, PA-RL dilutions are used for the treatment of EOC, non-cancer and fibroblast cell lines, revealing a selectivity of PA-RL, which induces a significantly higher cytotoxic effect in EOC with respect to non-cancer cells.

Gas Plasma-Conditioned Ringer's Lactate Enhances the Cytotoxic Activity of Cisplatin and Gemcitabine in Pancreatic Cancer In Vitro and In Ovo

Pancreatic cancer is one of the most aggressive tumor entities. Diffuse metastatic infiltration of vessels and the peritoneum restricts curative surgery. Standard chemotherapy protocols include the cytostatic drug gemcitabine with limited efficacy at considerable toxicity. In search of a more effective and less toxic treatment modality, we tested in human pancreatic cancer cells (MiaPaca and PaTuS) a novel combination therapy consisting of cytostatic drugs (gemcitabine or cisplatin) and gas plasma-conditioned Ringer’s lactate that acts via reactive oxygen species. A decrease in metabolic activity and viability, change in morphology, and cell cycle arrest was observed in vitro. The combination treatment was found to be additively toxic. The findings were validated utilizing an in ovo tumor model of solid pancreatic tumors growing on the chorion-allantois membrane of fertilized chicken eggs (TUM-CAM). The combination of the drugs (especially cisplatin) with the plasma-conditioned liquid significantly enhanced the anti-cancer effects, resulting in the induction of cell death, cell cycle arrest, and inhibition of cell growth with both of the cell lines tested. In conclusion, our novel combination approach may be a promising new avenue to increase the tolerability and efficacy of locally applied chemotherapeutic in diffuse metastatic peritoneal carcinomatosis of the pancreas.

Sublethal treatment with plasma-activated medium induces senescence-like growth arrest of A549 cells: involvement of intracellular mobile zinc

Plasma-activated medium (PAM) is a solution produced by exposing a liquid medium to non-thermal atmospheric pressure plasma (NTAPP). A number of reactive molecules, such as reactive oxygen species and reactive nitrogen species, are contained in PAM. Therefore, exposure to high doses of PAM results in cell death. We previously demonstrated that intracellular zinc (Zn²⁺) serves as an important mediator in PAM-induced cell death; however, the effects of sublethal treatment with PAM on cell functions are not fully understood. In the present study, we found that sublethal PAM treatment suppressed cell proliferation and induced senescence-like changes in lung adenocarcinoma A549 cells. Cell cycle analysis revealed that PAM induced cell cycle arrest at the G2/M phase. PAM increased the level of intracellular free Zn²⁺ and the Zn²⁺ chelator TPEN counteracted PAM-induced growth suppression, suggesting that Zn²⁺ functions in PAM-induced growth suppression. In addition, sublethal treatment with PAM induced phosphorylation of ATM kinase, accumulation of p53 protein, and expression of p21 and GADD45A, which are known p53 target genes, in a Zn²⁺-dependent manner. These results suggest that the induction of growth arrest and cellular senescence by sublethal PAM treatment is mediated by Zn²⁺-dependent activation of the ATM/p53 pathway.