Mitofusins modulate the increase in mitochondrial length, bioenergetics and secretory phenotype in therapy-induced senescent melanoma cells

Abstract

Cellular senescence is an endpoint of chemotherapy, and targeted therapies in melanoma and the senescence-associated secretory phenotype (SASP) can affect tumor growth and microenvironment, influencing treatment outcomes. Metabolic interventions can modulate the SASP, and an enhanced mitochondrial energy metabolism supports resistance to therapy in melanoma cells. Herein, we assessed the mitochondrial function of therapy-induced senescent melanoma cells obtained after exposing the cells to temozolomide (TMZ), a methylating chemotherapeutic agent. Senescence induction in melanoma was accompanied by a substantial increase in mitochondrial basal, ATP-linked, and maximum respiration rates and in coupling efficiency, spare respiratory capacity, and respiratory control ratio. Further examinations revealed an increase in mitochondrial mass and length. Alterations in mitochondrial function and morphology were confirmed in isolated senescent cells, obtained by cell-size sorting. An increase in mitofusin 1 and 2 (MFN1 and 2) expression and levels was observed in senescent cells, pointing to alterations in mitochondrial fusion. Silencing mitofusin expression with short hairpin RNA (shRNA) prevented the increase in mitochondrial length, oxygen consumption rate and secretion of interleukin 6 (IL-6), a component of the SASP, in melanoma senescent cells. Our results represent the first in-depth study of mitochondrial function in therapy-induced senescence in melanoma. They indicate that senescence increases mitochondrial mass, length and energy metabolism; and highlight mitochondria as potential pharmacological targets to modulate senescence and the SASP.

Mesenchymal Stromal Cells From Emphysematous Donors and Their Extracellular Vesicles Are Unable to Reverse Cardiorespiratory Dysfunction in Experimental Severe Emphysema

“…These findings are indeed consistent with the presence of elongated giant mitochondria in E-MSCs. Similar observations were found in senescent cancer cells with mitochondrial dysfunction ( Martínez et al, 2019 ). In addition to protein expression, mitochondrial fusion/fission balance is highly regulated by phosphorylation.…”

Mitochondrial ROS promote mitochondrial dysfunction and inflammation in ischemic acute kidney injury by disrupting TFAM-mediated mtDNA maintenance

“…Ultrathin sections prepared from the embedded tissues were stained with 5% uranyl acetate and lead citrate solution and observed by TEM (H-600, Hitachi, Ltd., Tokyo, Japan). Mitochondrial length/width ratio and average area were measured using ImageJ software (NIH, MD, USA) as previously described 24 , 25 . In brief, ~15 mitochondria in each image were randomly selected, and the mitochondrial length and width were traced and measured using the Length parameter; mitochondrial area was measured using the Area parameter.…”

Mitochondrial Bioenergetics and Dynamics in Secretion Processes

“…Work by others and us shows that impairment of mitochondrial catabolism and dynamics affects the secretion processes (6,7,(19)(20)(21)(22)(23)(24)(25)(26) and can underlie pathology in endocrine and neurodegenerative diseases (27)(28)(29)(30). Relevant roles for mitochondria in protein secretion by immune and senescent cells have been recently described as well (19-21, 24-26, 31), underscoring the relevance of these interactions.…”

“…Multiple studies linking mitochondrial morphology and bioenergetics can be found in the literature (107)(108)(109). At the molecular level several reports support that MFN2 is required for correct mitochondrial function (110); since its silencing results in an impairment of oxidative phosphorylation, while overexpression enhances mitochondrial metabolism (19,(111)(112)(113). Less evidence supports a role for MFN1.…”