Viridiana Y. González-Puertos

Senescence associated secretory phenotype profile from primary lung mice fibroblasts depends on the senescence induction stimuli

Cellular senescence is a multifactorial phenomenon of growth arrest and distorted function, which has been recognized as an important feature during tumor suppression mechanisms and a contributor to aging. Senescent cells have an altered secretion pattern called Senescence-Associated Secretory Phenotype (SASP) that comprises a complex mix of factors including cytokines, growth factors, chemokines, and matrix metalloproteinases. SASP has been related with local inflammation that leads to cellular transformation and neurodegenerative diseases. Various pathways for senescence induction have been proposed; the most studied is replicative senescence due to telomere attrition called replicative senescence (RS). However, senescence can be prematurely achieved when cells are exposed to diverse stimuli such as oxidative stress (stress-induced premature senescence, SIPS) or proteasome inhibition (proteasome inhibition-induced premature senescence, PIIPS). SASP has been characterized in RS and SIPS but not in PIIPS. Hence, our aim was to determine SASP components in primary lung fibroblasts obtained from CD-1 mice induced to senescence by PIIPS and compare them to RS and SIPS. Our results showed important variations in the 62 cytokines analyzed, while SIPS and RS showed an increase in the secretion of most cytokines, and in PIIPS only 13 were incremented. Variations in glutathione-redox balance were also observed in SIPS and RS, and not in PIIPS. All senescence types SASP displayed a pro-inflammatory profile and increased proliferation in L929 mice fibroblasts exposed to SASP. However, the behavior observed was not exactly the same, suggesting that the senescence induction pathway might encompass dissimilar responses in adjacent cells and promote different outcomes.

A noncanonical NF-κB pathway through the p50 subunit regulates Bcl-2 overexpression during an oxidative-conditioning hormesis response

Cells can respond to damage and stress by activating various repair and survival pathways. One of these responses can be induced by preconditioning the cells with sublethal stress to provoke a prosurvival response that will prevent damage and death, and which is known as hormesis. Bcl-2, an antiapoptotic protein recognized by its antioxidant and prosurvival functions, has been documented to play an important role during oxidative-conditioning hormesis. Using an oxidative-hormetic model, which was previously established in the L929 cell line by subjecting the cells to a mild oxidative stress of 50 μM H₂O₂ for 9 h, we identified two different transductional mechanisms that participate in the regulation of Bcl-2 expression during the hormetic response. These mechanisms converge in activating the nuclear transcription factor NF-κB. Interestingly, the noncanonical p50 subunit of the NF-κB family is apparently the subunit that participates during the oxidative-hormetic response.

Primary cultured astrocytes from old rats are capable to activate the Nrf2 response against MPP+ toxicity after tBHQ pretreatment

Astrocytes are key players for brain physiology, protecting neurons by releasing antioxidant enzymes; however, they are also susceptible to damage by neurotoxins. Nuclear factor erythroid-derived 2-like 2 (Nrf2) is a central regulator of the antioxidant response, and therefore, pharmacologic inducers are often used to activate this transcription factor to induce cellular protection. To date, it still remains unknown if cells from aged animals are capable of developing this response. Therefore, the purpose of this work was to determine if cortical astrocytes derived from old rats are able to respond to tertbuthyl-hydroquinene (tBHQ) pretreatment and stimulate the Nrf2-antioxidant response pathway to induce an antioxidant strategy against MPP+ toxicity, one of the most used molecules to model Parkinsons disease. Our results show that, although astrocytes from adult and old rats were more susceptible to MPP+ toxicity than astrocytes from newborn rats, when pretreated with tertbuthyl-hydroquinene, they were able to transactivate Nrf2, increasing antioxidant enzymes and developing cellular protection. These results are discussed in terms of the doses used to create protective responses.

New considerations on hormetic response against oxidative stress

In order to survive living organisms have developed multiple mechanisms to deal with tough environmental conditions. Hormesis is defined as a process in which exposure to a low dose of a chemical agent or environmental factor that is damaging at higher doses induces an adaptive beneficial effect on the cell or organism. In this paper, we examine several ideas that might be taken into consideration before using hormesis as a therapeutic tool to improve health and life span, and hopefully will open the discussion for new and interesting debates regard hormesis. The first one is to understand that the same stressor or inductor can activate different pathways in a parallel or dual response, which might lead to diverse outcomes. Another idea is related to the mechanisms involved in activating Nrf2, which might be different and have diverse hormetic effects.Last, we discuss mild oxidative stress in association to low-grade chronic inflammation as a stimulating avenue to be explored and the unexpected effects proposed by the obesity paradox theory. All the previous might help to clarify the reasons why centenarians are able to reach the extreme limits of human life span, which could probably be related to the way they deal with homeostasis maintenance, providing an opportunity for hormesis to intervene significantly.

Immunization with a Neural-Derived Peptide Protects the Spinal Cord from Apoptosis after Traumatic Injury

Apoptosis is one of the most destructive mechanisms that develop after spinal cord (SC) injury. Immunization with neural-derived peptides (INDPs) such as A91 has shown to reduce the deleterious proinflammatory response and the amount of harmful compounds produced after SC injury. With the notion that the aforementioned elements are apoptotic inducers, we hypothesized that INDPs would reduce apoptosis after SC injury. In order to test this assumption, adult rats were subjected to SC contusion and immunized either with A91 or phosphate buffered saline (PBS; control group). Seven days after injury, animals were euthanized to evaluate the number of apoptotic cells at the injury site. Apoptosis was evaluated using DAPI and TUNEL techniques; caspase-3 activity was also evaluated. To further elucidate the mechanisms through which A91 exerts this antiapoptotic effects we quantified tumor necrosis factor-alpha (TNF-α). To also demonstrate that the decrease in apoptotic cells correlated with a functional improvement, locomotor recovery was evaluated. Immunization with A91 significantly reduced the number of apoptotic cells and decreased caspase-3 activity and TNF-α concentration. Immunization with A91 also improved the functional recovery of injured rats. The present study shows the beneficial effect of INDPs on preventing apoptosis and provides more evidence on the neuroprotective mechanisms exerted by this strategy.

DNA MMR systems, microsatellite instability and antioxidant activity variations in two species of wild bats: Myotis velifer and Desmodus rotundus, as possible factors associated with longevity

The accumulation of oxidative damage to biomolecules, such as DNA, is known to induce alterations in the cells mechanisms and structure that might lead to the aging process. DNA mismatch repair system (MMR) corrects base mismatches generated during DNA replication that have escaped the proofreading process. In addition, antioxidant enzymes can reduce reactive oxygen species effects in order to protect cells from oxidizing damage. In order to determine the importance of these associated factors during the aging process, in this study, levels of MMR proteins MSH2 and MLH1, as well as microsatellite markers, were compared in liver, lung, and brain of juvenile, adult, and old, both female and male, individuals from two species of wild bats: the short-lived Myotis velifer and the longer lived Desmodus rotundus. Catalase, glutathione peroxidase, and superoxide dismutase were also analyzed to determine if the antioxidant protection correlates negatively with DNA damage. Antioxidant activities were higher in the longer lived D. rotundus than in M. velifer. Furthermore, old M. velifer but not old D. rotundus bats had reduced MMR levels and increased microsatellite instability. Therefore, although our results correlate the reduced MMR efficiency, the deficient antioxidant activity, and the increase in DNA damage with the aging process, this is not always true for all living organisms.

Comparing the effects of two neurotoxins in cortical astrocytes obtained from rats of different ages: involvement of oxidative damage

Oxidative stress has been recognized as a potential mediator of cell death. Astrocytes play an active role in brain physiology responding to harmful stimuli by activating astrogliosis, which in turn has been associated either with survival or degenerative events. The characterization of the mechanistic actions exerted by different toxins in astrocytes is essential to understand the brain function and pathology. As age plays a critical role in degenerative processes, the aim of this study was to determine whether the administration of equimolar concentrations of two neurotoxins evoking different toxic patterns can induce differential effects on primary astrocytes obtained either from newborn or adult rats, with particular emphasis on those events linked to oxidative stress as a potential source of damage. Primary cortical astrocyte cultures derived from rat brains were exposed to 1‐methyl‐4‐phenylpyridinium (MPP+) or beta‐amyloid peptide (β‐amyloid). Mitochondrial functionality and cell viability were determined as physiological parameters, whereas lipid and protein oxidation were used as markers of oxidative damage. The results of these experiments pointed towards a higher vulnerability to MPP + over β‐amyloid, on most of the tested markers. Hence, in order to allow a comprehensive evaluation of astrocytic responses against MPP + intoxication, a third astrocyte group was included for dose‐response experiments: astrocytes derived from aged rats. The present data indicate that the differences associated with age were mainly found in astrocytes exposed to MPP + (25 and 50 μM) at 1‐h treatment. Results are discussed in terms of the differential mechanisms involved in each model. Copyright

Relationship of inflammatory profile of elderly patients serum and senescence-associated secretory phenotype with human breast cancer cells proliferation: Role of IL6/IL8 ratio

HIGHLIGHTSOnly certain elderly patients serum were capable to induce MCF‐7 proliferation.The SASP from WI‐38‐senescent cells also induced MCF‐7 cellular proliferation.An inflammatory profile is required to induce MCF‐7 cellular proliferation.An IL‐6/IL 8 specific ratio is required within the inflammatory profile.Only EPS‐IP and IL‐6/IL‐8 ratio 3.0 treatment increased Cyclin D1 expression in MCF‐7 cells. ABSTRACT Aging is considered a systemic, chronic and low‐grade inflammatory state, called “inflammaging”, which has been contemplated as a risk factor for cancer development and progression in the elderly population. Cellular senescence is a multifactorial phenomenon of growth arrest and distorted function, which has been recognized as a contributor to aging. Senescent cells have an altered secretion pattern called Senescent Associated Secretory Phenotype (SASP), that comprise a complex mix of factors including cytokines, growth factors, chemokines and matrix metalloproteinases among others. The SASP secreted by accumulated senescent cells during old age has been related to local inflammation that leads to cellular transformation and therefore may be supporting the inflammaging process. Here, we evaluated if the pro‐inflammatory profile within the serum obtained from elderly patients (EPS) was able to induce cellular proliferation in the breast cancer transformed cell line (MCF‐7), in a similar way to the proliferation stimulated by the SASP obtained from WI‐38 primary cells prematurely induced to senescence by oxidative stress (SIPS). At the same time, the participation of IL‐6/IL‐8 ratio was determined. Our results showed that not all the EPS increased MCF‐7 proliferation. However, there was an interesting relationship between IL‐6 and IL‐8 concentrations, when the IL‐6 was higher than IL‐8. Similar results were found with SASP from SIPS‐WI‐38 on the MCF‐7 proliferation. Although it is known that those cytokines are fundamental factors to induce proliferation; the occurrence of other components in the cellular microenvironment is necessary to carry out this effect.

Cellular Senescence, Neurological Function, and Redox State

SIGNIFICANCE Cellular senescence, characterized by permanent cell cycle arrest, has been extensively studied in mitotic cells such as fibroblasts. However, senescent cells have also been observed in the brain. Even though it is recognized that cellular energetic metabolism and redox homeostasis are perturbed in the aged brain and neurodegenerative diseases (NDDs), it is still unknown which alterations in the overall physiology can stimulate cellular senescence induction and their relationship with the former events. Recent Advances: Recent findings have shown that during prolonged inflammatory and pathologic events, the blood-brain barrier could be compromised and immune cells might enter the brain; this fact along with the brains high oxygen dependence might result in oxidative damage to macromolecules and therefore senescence induction. Thus, cellular senescence in different brain cell types is revised here. CRITICAL ISSUES Most information related to cellular senescence in the brain has been obtained from research in glial cells since it has been assumed that the senescent phenotype is a feature exclusive to mitotic cells. Nevertheless, neurons with senescence hallmarks have been observed in old mouse brains. Therefore, although this is a controversial topic in the field, here we summarize and integrate the observations from several studies and propose that neurons indeed senesce. FUTURE DIRECTIONS It is still unknown which alterations in the overall metabolism can stimulate senescence induction in the aged brain, what are the mechanisms and signaling pathways, and what is their relationship to NDD development. The understanding of these processes will expose new targets to intervene age-associated pathologies.-Antioxid. Redox Signal. 28, 1704-1723.