Caveolae and Rho Kinase: their implication of the senescent cell morphology and the secretion of the SASP in HeLa and A549 cancer cells.

Purpose: Caveolae and Rho kinase signaling individually are both remodeled during cellular senescence and influence cell morphology and SASP secretion. However, how this interaction modulates senescent cancer-cell morphology and SASP remains unresolved. We evaluated the possible connection between caveolae and ROCK on the development of senescent cell morphology and the secretion of the SASP.

Methods: Senescence was induced in HeLa and A549 cells with ouabain. Caveolin depletion was achieved with methyl-beta-cyclodextrin (MβCD) or Caveolin-1 siRNA applications. Cell morphology was assessed by cell area, volume, and thickness parameters, while SASP secretion was assessed by measuring total protein, IL-6, and VEGF-A in senescent cell secretomes. We also evaluated the effect of caveolae depletion on ROCK expression, activation, and localization.

Results: While the caveolae disruption with the preincubation of MβCD did not alter the occurrence of ouabain-induced senescence, it significantly altered cellular morphological features, such as decreased cell area and volume. The amount of ROCK1 and ROCK2 in the membrane fraction of cells was decreased by MβCD preincubation. These findings indicate that there may be a relationship between ROCK and the morphological changes observed in senescent cells as a result of the disruption of the caveolar structure. However, the incubation of MβCD and caveolin-1 knocking down increased the secretory activity of senescent cells. Overall secretion increases with caveolar depletion, indicating that its secretion-enhancing effect is greater than any concomitant decrease that may occur with ROCK inhibition.

Conclusion: These data suggest that maintaining the integrity of caveolar structures plays a critical role in mitigating the detrimental effects of SASP released from chemotherapy-induced senescent cells.