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Reversibility of apoptosis in primary rat heart cells, ferret brain cells, and primary mouse macrophages. (A) Schematic diagram of approach using annexin V-FITC to track cells that reverse apoptosis. (B) Confocal and DIC microscopy of rat primary heart cells that were exposed to 4.5% ethanol for 5 h (Treated) or not (Untreated). Treated cells were then washed to remove apoptotic inducers and further cultured for 2 h (Washed). Merged images, mitochondria (red), nuclei (blue), and annexin V-FITC (annexin V)-labeled exposed phosphatidylserine (PS) (green) were visualized by fluorescence, and cell morphology was by DIC. Scale bar, 10 μm. (C) Quantification of the apoptotic response and its reversal on primary rat heart cells and Mpf brain cells. Percentage of cells showing morphological signs of apoptosis including mitochondrial fragmentation, nuclear condensation, cell shrinkage, and cell surface phosphatidylserine labeled with annexin V-FITC (Annexin V) for control cells (Untreated), cells treated with apoptotic inducer (heart cells with 4.5% ethanol for 5 h, brain cells with 2 μM jasplakinolide for 50 h) (Treated), and treated cells that were washed and further cultured with fresh medium (heart cells for 2 h, brain cells for 3 h) in standard conditions (Washed). *p < 0.01; n = 3 independent experiments. Error bars denote SD. (D) Fluorescence of healthy, untreated macrophages, those that were exposed to 1 μM cucurbitacin I (CuI) for 24 h (Treated), and treated cells that were washed to remove apoptotic inducers and further cultured for 24 h (Washed). Merged images, mitochondria (red) and nuclei (blue). Scale bar, 30 μm. (E) Percentage of the untreated, treated, and washed macrophages that displayed mitochondrial fragmentation, nuclear condensation, and cell shrinkage. *p < 0.01; n = 3 independent experiments. Error bars denote SD.
Source publication
Apoptosis serves as a protective mechanism by eliminating damaged cells through programmed cell death. After apoptotic cells pass critical checkpoints, including mitochondrial fragmentation, executioner caspase activation, and DNA damage, it is assumed that cell death inevitably follows. However, this assumption has not been tested directly. Here w...
Contexts in source publication
Context 1
... of >30 living cells in a single field showed morphological recovery of the majority of them after removal of the apoptotic stim- ulus (Supplemental Figure S2). In contrast, virtually all cells died when they were left in the inducer (Supplemental Figure S3). ...
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... of apoptosis also occurred in primary rat heart cells ex- posed to 4.5% ethanol for 5 h, in Mustela putoris furo (Mpf) brain cells (CRL1516) exposed to 2 μM jasplakinolide for 50 h (Figure 2, A-C), and in primary mouse macrophages exposed to 1 μM cucur- bitacin I for 24 h ( Figure 2, D and E). Greater than 90% of each cell type displayed morphological hallmarks of apoptosis, including nu- clear condensation, mitochondrial fragmentation, and cell shrinkage. ...
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... removal of the inducer for 24 h, ∼90% of the cells recovered morphology. Fluorescently labeled annexin V was also used to track reversal of apoptosis in heart and brain cells ( Figure 2A). Annexin V binds efficiently to phosphatidylserine, which moves from the inner to the outer leaflet of the plasma membrane during apoptosis (Logue et al., 2009). ...
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... V binds efficiently to phosphatidylserine, which moves from the inner to the outer leaflet of the plasma membrane during apoptosis (Logue et al., 2009). Ten minutes before washing, fluorescein isothiocyanate- conjugated annexin V (annexin V-FITC) was applied to label apop- totic cells ( Figure 2B), and >90% of both cell types were labeled ( Figure 2, B and C). After removal of the inducer for 2 h to heart and 3 h to brain cells, >20% of heart cells and 60% of brain cells retained the annexin V-FITC label after morphological recovery ( Figure 2, B and C). ...
Context 5
... V binds efficiently to phosphatidylserine, which moves from the inner to the outer leaflet of the plasma membrane during apoptosis (Logue et al., 2009). Ten minutes before washing, fluorescein isothiocyanate- conjugated annexin V (annexin V-FITC) was applied to label apop- totic cells ( Figure 2B), and >90% of both cell types were labeled ( Figure 2, B and C). After removal of the inducer for 2 h to heart and 3 h to brain cells, >20% of heart cells and 60% of brain cells retained the annexin V-FITC label after morphological recovery ( Figure 2, B and C). ...
Context 6
... minutes before washing, fluorescein isothiocyanate- conjugated annexin V (annexin V-FITC) was applied to label apop- totic cells ( Figure 2B), and >90% of both cell types were labeled ( Figure 2, B and C). After removal of the inducer for 2 h to heart and 3 h to brain cells, >20% of heart cells and 60% of brain cells retained the annexin V-FITC label after morphological recovery ( Figure 2, B and C). This provides an additional strategy to track cells that un- dergo apoptosis and survive, without the need of transfection. ...
Citations
... 79 vation and DNA damage. 72 Similarly, identical bioelectric manipulations and V mem changes can promote both proliferation and apoptosis. Additionally, hyperpolarization via K + channel activation, instead of causing proliferation, protects cells against cell death. ...
Ion gradients across cell membranes generate voltage potentials that are involved in a wide range of biological processes. According to the membrane hypothesis of aging, aging is inextricably linked to a decrease in resting membrane potential (Vmem). Alterations in ion channel activity and membrane fluidity caused by aging disrupt bioelectric homeostasis, increase intracellular calcium and potassium concentrations, induce abnormal mechanistic target of rapamycin (MTOR)‐ and AMPK‐regulated metabolism and energy dissipation, and decrease proliferation and regeneration. Failure to maintain ion channel activity and membrane potential leads to cell senescence or death. There is evidence that by manipulating ion channel activities, a cryptic memory can be recalled to restore lost proliferative or regenerative abilities. Reversal or prevention of senescence, aging phenotypes, and longevity may be achieved by fine‐tuning mitochondrial membrane polarization. Therefore, there is optimism that deciphering the bioelectric codes that govern cell functions will lead to the development of new gero‐electroceuticals that restore cell function and prevent tissue loss during aging.
... 4,5 There appears to be potential for repairing cells that are in a pre-apoptotic state. 15 Reversal of apoptotic processes by DNA repair has been demonstrated in diabetic mice where leukostasis, cell death, and vascular permeability were abrogated. 16 Furthermore, it has been shown that in some circumstances apoptosis can be reversed at a later stage despite caspase activation. ...
... 16 Furthermore, it has been shown that in some circumstances apoptosis can be reversed at a later stage despite caspase activation. 15 We previously have demonstrated the generation of a BRVO in the pig model. 4,6,8,17 This model uses intravenous Rose Bengal dye as a photothrombotic agent allowing an intravenous thrombosis to occur and limiting the amount of laser irradiation to the vein. ...
Purpose:
To compare gene expression changes following branch retinal vein occlusion (BRVO) in the pig with and without bevacizumab (BEV) and triamcinolone acetonide (TA).
Methods:
Photothrombotic BRVOs were created in both eyes of four groups of nine pigs (2, 6, 10, and 20 days). In each group, six pigs received intravitreal injections of BEV in one eye and TA in the fellow eye, with three pigs serving as untreated BRVO controls. Three untreated pigs served as healthy controls. Expression of mRNA of vascular endothelial growth factor (VEGF), glial fibrillary acidic protein (GFAP), dystrophin (DMD), potassium inwardly rectifying channel subfamily J member 10 protein (Kir4.1, KCNJ10), aquaporin-4 (AQP4), stromal cell-derived factor-1α (CXCL12), interleukin-6 (IL6), interleukin-8 (IL8), monocyte chemoattractant protein-1 (CCL2), intercellular adhesion molecule 1 (ICAM1), and heat shock factor 1 (HSF1) were analyzed by quantitative reverse-transcription polymerase chain reaction. Retinal VEGF protein levels were characterized by immunohistochemistry.
Results:
In untreated eyes, BRVO significantly increased expression of GFAP, IL8, CCL2, ICAM1, HSF1, and AQP4. Expression of VEGF, KCNJ10, and CXCL12 was significantly reduced by 6 days post-BRVO, with expression recovering to healthy control levels by day 20. Treatment with BEV or TA significantly increased VEGF, DMD, and IL6 expression compared with untreated BRVO eyes and suppressed BRVO-induced CCL2 and AQP4 upregulation, as well as recovery of KCNJ10 expression, at 10 to 20 days post-BRVO.
Conclusions:
Inflammation and cellular osmohomeostasis rather than VEGF suppression appear to play important roles in BRVO-induced retinal neurodegeneration, enhanced in both BEV- and TA-treated retinas.
Translational relevance:
Inner retinal neurodegeneration seen in this acute model of BRVO appears to be mediated by inflammation and alterations in osmohomeostasis rather than VEGF inhibition, which may have implications for more specific treatment modalities in the acute phase of BRVO.
... The term "anastasis" refers to a homeostatic process that enables mammalian cells to recover after engaging regulated cell death [81,84,85,87,94,95]]. Like the prosurvival function of caspase 3, anastasis poses an obvious challenge in cancer therapy. ...
... The term "anastasis" refers to a homeostatic process that enables mammalian cells to recover after engaging regulated cell death [81,84,85,87,94,95]]. Like the prosurvival function of caspase 3, anastasis poses an obvious challenge in cancer therapy. Thus, cancer cells triggered to undergo apoptosis (e.g., in response to chemotherapeutic drugs) can recover from the late stages of apoptosis (even after the formation of apoptotic bodies) [91,94] and give rise to aggressive variants with increased aneuploidy [94,95]. (This calls for revisiting thousands of articles that use the terms "apoptosis" and "lethality" interchangeably!). ...
... The term "anastasis" refers to a homeostatic process that enables mammalian cells to recover after engaging regulated cell death [81,84,85,87,94,95]]. Like the prosurvival function of caspase 3, anastasis poses an obvious challenge in cancer therapy. Thus, cancer cells triggered to undergo apoptosis (e.g., in response to chemotherapeutic drugs) can recover from the late stages of apoptosis (even after the formation of apoptotic bodies) [91,94] and give rise to aggressive variants with increased aneuploidy [94,95]. (This calls for revisiting thousands of articles that use the terms "apoptosis" and "lethality" interchangeably!). ...
The many limitations of implementing anticancer strategies under the term “precision oncology” have been extensively discussed. While some authors propose promising future directions, others are less optimistic and use phrases such as illusion, hype, and false hypotheses. The reality is revealed by practicing clinicians and cancer patients in various online publications, one of which has stated that “in the quest for the next cancer cure, few researchers bother to look back at the graveyard of failed medicines to figure out what went wrong”. The message is clear: Novel therapeutic strategies with catchy names (e.g., synthetic “lethality”) have not fulfilled their promises despite decades of extensive research and clinical trials. The main purpose of this review is to discuss key challenges in solid tumor therapy that surprisingly continue to be overlooked by the Nomenclature Committee on Cell Death (NCCD) and numerous other authors. These challenges include: The impact of chemotherapy-induced genome chaos (e.g., multinucleation) on resistance and relapse, oncogenic function of caspase 3, cancer cell anastasis (recovery from late stages of apoptosis), and pitfalls of ubiquitously used preclinical chemosensitivity assays (e.g., cell “viability” and tumor growth delay studies in live animals) that score such pro-survival responses as “lethal” events. The studies outlined herein underscore the need for new directions in the management of solid tumors.
... These findings could be related to increased levels of apoptosis and a decrease in cell proliferation, as described. Anticancer effects of several drugs have been described to promote G0/G1 cell cycle arrest and apoptosis such as 2,4-dinitrobenzenesulfonamide derivative in acute leukemia cells [29], TH-39 in K562 cells [30], Mere 15 in K562 cells [31] and thio-Cl-IB-MECA in HL-60 cells [32]. D-Cyclins 1 and 2 (CCND1, CCND2) are key elements in the control of cell cycle progression from G1 to S phases [33,34]. ...
Leukemias are among the most prevalent types of cancer worldwide. Bone marrow mesenchymal stem cells (MSCs) participate in the development of a suitable niche for hematopoietic stem cells, and are involved in the development of diseases such as leukemias, to a yet unknown extent. Here we described the effect of secretome of bone marrow MSCs obtained from healthy donors and from patients with acute myeloid leukemia (AML) on leukemic cell lineages, sensitive (K562) or resistant (K562-Lucena) to chemotherapy drugs. Cell proliferation, viability and death were evaluated, together with cell cycle, cytokine production and gene expression of ABC transporters and cyclins. The secretome of healthy MSCs decreased proliferation and viability of both K562 and K562‑Lucena cells; moreover, an increase in apoptosis and necrosis rates was observed, together with the activation of caspase 3/7, cell cycle arrest in G0/G1 phase and changes in expression of several ABC proteins and cyclins D1 and D2. These effects were not observed using the secretome of MSCs derived from AML patients. In conclusion, the secretome of healthy MSCs have the capacity to inhibit the development of leukemia cells, at least in the studied conditions. However, MSCs from AML patients seem to have lost this capacity, and could therefore contribute to the development of leukemia.
... Apoptosis is characterized by hallmarks such as membrane blebbing, nuclear condensation and 253 fragmentation, mitochondrial fragmentation, PS exposure, and caspase activation [49] . Canonical 254 apoptosis has been considered as a non-reversible cell-death pathway; however, recent studies 255 have shown that cells can recover even after displaying apoptosis hallmarks [50,51,52] . Neurons 256 ...
While traditionally studied for their pro-apoptotic functions, recent research suggests BH3-only proteins also have non-apoptotic roles. Here, we find that EGL-1, the BH3-only protein in Caenorhabditis elegans , promotes the cell-autonomous production of exophers in adult neurons. Exophers are large, micron-scale vesicles that are ejected from the cell and contain cellular components such as mitochondria. EGL-1 facilitates exopher production potentially through regulation of mitochondrial dynamics. Moreover, an endogenous, low level of EGL-1 expression appears to benefit dendritic health. Our findings provide insights into the mechanistic role of BH3-only protein in mitochondrial dynamics, downstream exopher production, and ultimately neuronal health.
Significance statement
BH3-only proteins were known for their function in inducing cell death. Their presence in healthy adult neurons, however, suggests additional roles. Our study focused on the BH3-only protein EGL-1 in the nematode Caenorhabditis elegans , where its apoptotic role was discovered. We reveal a new role in cell-autonomously promoting exopher production – a process where neurons extrude large vesicles containing potentially harmful cell contents. EGL-1 appears to promote this by regulating mitochondrial dynamics. We also report that low levels of EGL-1 benefit neuronal health and function. These findings expand our understanding of BH3-only proteins, mitochondrial dynamics, and exopher production in neurons and provide insights for neurodegenerative diseases.
... However, programmed cellular death is not necessarily an isolated outcome that reflects toxicity or poor tissue health. Recently, it has been identified that cells can recover from apoptosis after events including caspase-activation, mitochondrial fragmentation, and DNA damage (46). A separate cell death pathway, ferroptosis, was also found to be reversible (47). ...
... Mechanisms through which cells can recover from death pathways may serve to protect valuable cell populations such as cardiomyocytes. However, such processes also drive DNA damage, micronuclei formation, and massive genetic rearrangements, which can lead to cancerous mutations and deleterious phenotypes (46). Not surprisingly, RNA transcription was proposed to be a critical step in apoptosis recovery (46). ...
... However, such processes also drive DNA damage, micronuclei formation, and massive genetic rearrangements, which can lead to cancerous mutations and deleterious phenotypes (46). Not surprisingly, RNA transcription was proposed to be a critical step in apoptosis recovery (46). Thus, cells undergoing recovery from a death pathway might be expected to release different sets of EV-encapsulated cargo than homeostatic cells. ...
Detrimental side effects of drugs like doxorubicin, which can cause cardiotoxicity, pose barriers for preventing cancer progression, or treating cancer early through molecular interception. Extracellular vesicles (EVs) are valued for their potential as biomarkers of human health, chemical and molecular carcinogenesis, and therapeutics to treat disease at the cellular level. EVs are released both during normal growth and in response to toxicity and cellular death, playing key roles in cellular communication. Consequently, EVs may hold promise as precision biomarkers and therapeutics to prevent or offset damaging off-target effects of chemotherapeutics. EVs have promise as biomarkers of impending cardiotoxicity induced by chemotherapies and as cardioprotective therapeutic agents. However, EVs can also mediate cardiotoxic cues, depending on the identity and past events of their parent cells. Understanding how EVs mediate signaling is critical toward implementing EVs as therapeutic agents to mitigate cardiotoxic effects of chemotherapies. For example, it remains unclear how mixtures of EV populations from cells exposed to toxins or undergoing different stages of cell death contribute to signaling across cardiac tissues. Here, we present our perspective on the outlook of EVs as future clinical tools to mitigate chemotherapy-induced cardiotoxicity, both as biomarkers of impending cardiotoxicity and as cardioprotective agents. Also, we discuss how heterogeneous mixtures of EVs and transient exposures to toxicants may add complexity to predicting outcomes of exogenously applied EVs. Elucidating how EV cargo and signaling properties change during dynamic cellular events may aid precision prevention of cardiotoxicity in anticancer treatments and development of safer chemotherapeutics.
... The term "anastasis" refers to a homeostatic process that enables mammalian cells to recover after engaging regulated cell death [81,84,85,87,94,95]]. Like prosurvival function of caspase 3, anastasis poses an obvious challenge in cancer therapy. ...
... The term "anastasis" refers to a homeostatic process that enables mammalian cells to recover after engaging regulated cell death [81,84,85,87,94,95]]. Like prosurvival function of caspase 3, anastasis poses an obvious challenge in cancer therapy. Thus, cancer cells triggered to undergo apoptosis (e.g., in response to chemotherapeutic drugs) can recover from late stages of apoptosis (even after formation of apoptotic bodies) [91,94] and give rise to aggressive variants with increased aneuploidy [94,95]. (This calls for revisiting thousands of articles that use the terms "apoptosis" and "lethality" interchangeably!) • Studies with adenocarcinoma tumor samples have revealed the presence of densely populated apoptotic cells within an individual tumor [96]. ...
... The term "anastasis" refers to a homeostatic process that enables mammalian cells to recover after engaging regulated cell death [81,84,85,87,94,95]]. Like prosurvival function of caspase 3, anastasis poses an obvious challenge in cancer therapy. Thus, cancer cells triggered to undergo apoptosis (e.g., in response to chemotherapeutic drugs) can recover from late stages of apoptosis (even after formation of apoptotic bodies) [91,94] and give rise to aggressive variants with increased aneuploidy [94,95]. (This calls for revisiting thousands of articles that use the terms "apoptosis" and "lethality" interchangeably!) • Studies with adenocarcinoma tumor samples have revealed the presence of densely populated apoptotic cells within an individual tumor [96]. ...
The many limitations of implementing anticancer strategies under the term “precision oncology” have been extensively discussed. While some authors propose promising future directions, others are less optimistic and use phrases such as illusion, hype and false hypotheses. The reality is revealed by practicing clinicians and cancer patients in various online publications, one of which has stated that “in the quest for the next cancer cure, few researchers bother to look back at the graveyard of failed medicines to figure out what went wrong.” The message is clear: novel therapeutic strategies with catchy names (e.g., synthetic “lethality”) have not fulfilled their promises despite decades of extensive research and clinical trials. The main purpose of this review is to discuss key challenges in solid tumor therapy that surprisingly continue to be overlooked by the nomenclature committee on cell death and numerous other authors. These challenges include: the impact of chemotherapy-induced genome chaos (e.g., multinucleation) on resistance and relapse, oncogenic function of caspase 3, cancer cell anastasis (recovery from late stages of apoptosis), and pitfalls of ubiquitously used preclinical chemosensitivity assays (e.g., cell “viability” and tumor growth delay studies in live animals) that score such pro-survival responses as “lethal” events. Studies outline herein underscore the need for new direction in the management of solid tumors.
... Smart drug delivery systems (DDS) can aid in the suppression of Cytc. While the recently discovered biochemical pathway of anastasis (Greek for "rising to life") challenges Cytc medication design [Tang et al. 2012;Tang and Tang 2018]. Anastasis denotes the recovery of dying cells from the edge of death, and it appears to be an intrinsic recovery phenomenon against apoptosis-induced cell death and probably other cell death mechanisms [Tang et al. 2012;Tang and Tang 2018]. ...
... While the recently discovered biochemical pathway of anastasis (Greek for "rising to life") challenges Cytc medication design [Tang et al. 2012;Tang and Tang 2018]. Anastasis denotes the recovery of dying cells from the edge of death, and it appears to be an intrinsic recovery phenomenon against apoptosis-induced cell death and probably other cell death mechanisms [Tang et al. 2012;Tang and Tang 2018]. Discovered that late-stage apoptosis may be reversible in HeLa cells, brain cells, and cervical cancer cells, among others [Tang and Tang 2018]. ...
Na,K-ATPase is a crucial enzyme responsible for maintaining Na⁺, K⁺-gradients across the cell membrane, which is essential for numerous physiological processes within various organs and tissues. Due to its significance in cellular physiology, inhibiting Na,K-ATPase can have profound physiological consequences. This characteristic makes it a target for various pharmacological applications, and drugs that modulate the pump’s activity are thus used in the treatment of several medical conditions. Cytochrome c (Cytc) is a protein with dual functions in the cell. In the mitochondria, it is essential for ATP synthesis and energy production. However, in response to apoptotic stimuli, it is released into the cytosol, where it triggers programmed cell death through the intrinsic apoptosis pathway. Aside from its role in canonical intrinsic apoptosis, Cytc also plays additional roles. For instance, Cytc participates in certain non-apoptotic functions –those which are less well-understood in comparison to its role in apoptosis. Within this in vitro study, we have shown the impact of Cytc on Na,K-ATPase for the first time. Cytc has a biphasic action on Na,K-ATPase, with activation at low concentrations (0.06 ng/ml; 6 ng/ml) and inhibition at high concentration (120 ng/ml). Cytc moreover displays isoform/subunit specificity and regulates the Na⁺ form of the enzyme, while having no effect on the activity or kinetic parameters of the K⁺-dependent form of the enzyme. Changing the affinity of p-chloromercuribenzoic acid (PCMB) by Cytc is therefore both a required and sufficient condition for confirming that PCMB and Cytc share the same target, namely the thiol groups of cysteine in Na,K-ATPase.
... Both Eph receptors and ephrin ligands are membrane-bound, thus eliciting a bidirectional signaling in the interacting pair of cells [248]. They constitute an intercellular communication mode with many functions, such as the formation of spatial boundaries during normal development [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. While they regulate processes such as proliferation, cell death, and invasion, it is their role in cell sorting and positioning that made their fame [249,250], for instance, in regulating the positioning of intestinal epithelial cells within the stem cell niche [244] and coordinating between intercellular communication, migration, and cell positioning [243]. ...
Studies trying to understand cell death, this ultimate biological process, can be traced back to a century ago. Yet, unlike many other fashionable research interests, research on cell death is more alive than ever. New modes of cell death are discovered in specific contexts, as are new molecular pathways. But what is “cell death”, really? This question has not found a definitive answer yet. Nevertheless, part of the answer is irreversibility, whereby cells can no longer recover from stress or injury. Here, we identify the most distinctive features of different modes of cell death, focusing on the executive final stages. In addition to the final stages, these modes can differ in their triggering stimulus, thus referring to the initial stages. Within this framework, we use a few illustrative examples to examine how intercellular communication factors in the demise of cells. First, we discuss the interplay between cell–cell communication and cell death during a few steps in the early development of multicellular organisms. Next, we will discuss this interplay in a fully developed and functional tissue, the gut, which is among the most rapidly renewing tissues in the body and, therefore, makes extensive use of cell death. Furthermore, we will discuss how the balance between cell death and communication is modified during a pathological condition, i.e., colon tumorigenesis, and how it could shed light on resistance to cancer therapy. Finally, we briefly review data on the role of cell–cell communication modes in the propagation of cell death signals and how this has been considered as a potential therapeutic approach. Far from vainly trying to provide a comprehensive review, we launch an invitation to ponder over the significance of cell death diversity and how it provides multiple opportunities for the contribution of various modes of intercellular communication.
... Anti-apoptotic activity of AC102 treatment were evaluated in an ethanol-challenged immortalized mouse hippocampal cell line (HT22) by evaluation of cell morphology as well as caspase 3/7 activity in vitro. In short, a previously described apoptosis-inducing ethanol (EtOH) assay using 4.5% EtOH treatment for 5 hours was utilized (Fig. 1d) [42]. For morphological analysis, 40,000 HT22 cells per well were seeded in 24-well plates and maintained under CO 2 at 37 0 C in DMEM medium containing 10% FCS for 24 hours. ...
... In our study, dose responsive anti-apoptotic effects of AC102 were observed in ethanol challenged HT22 cells on a morphological level, by measuring caspase 3/7 activity, as well as by evaluation of the protein-expression of cleaved caspase-3. EIT induces apoptosis via caspase-dependent pathways as well as mitochondrial stress [23], with similar characteristics to ethanol-induced apoptosis [42]. A concentration of 30 µM of AC102 was su cient to signi cantly attenuate apoptosis. ...
Sensorineural hearing loss (SNHL) is the most common sensory deficit worldwide. Due to the heterogeneity of causes for SNHL, effective treatment options remain scarce, creating an unmet need for novel drugs in the field of otology. Cochlear implantation (CI) currently is the only established method to restore hearing function in profound SNHL and deaf patients. The cochlear implant bypasses the non-functioning sensory hair cells (HCs) and electrically stimulates the neurons of the cochlear nerve. CI also benefits patients with residual hearing by combined electrical and auditory stimulation. However, the insertion of an electrode array into the cochlea induces an inflammatory response, characterized by the expression of pro-inflammatory cytokines, upregulation of reactive oxygen species, and apoptosis and necrosis of HCs, putting residual hearing at risk.
Here, we characterize the effects of the small molecule AC102, a pyridoindole, for its protective effects on residual hearing in CI. We show that AC102 significantly preserves hearing thresholds across the whole cochlea and confines the cochlear trauma to the directly mechanically injured area. In addition, AC102 significantly preserves auditory nerve fibers and inner HC synapses throughout the whole cochlea. AC102s effects are likely elicited during the inflammatory phase of electrode insertion trauma (EIT) and mediated by anti-apoptotic and anti-inflammatory properties, as uncovered by an in vitro assay of ethanol induced apoptosis and evaluation of mRNA expression of pro-inflammatory cytokines in an organotypic ex vivo model of EIT.
The results in this study highlight AC102 as a promising compound for the attenuation of EIT during CI. Moreover, as the inflammatory response in cochlear implantation shares similarities to other etiologies of SNHL, a beneficial effect of AC102 can be inferred for other inner ear conditions as well.
