A heart that beats for 500 years: age-related changes in cardiac proteasome activity, oxidative protein damage and expression of heat shock proteins, inflammatory factors, and mitochondrial complexes in Arctica islandica, the longest-living noncolonial animal

Abstract

Study of negligibly senescent animals may provide clues that lead to better understanding of the cardiac aging process. To elucidate mechanisms of successful cardiac aging, we investigated age-related changes in proteasome activity, oxidative protein damage and expression of heat shock proteins, inflammatory factors, and mitochondrial complexes in the heart of the ocean quahog Arctica islandica, the longest-lived noncolonial animal (maximum life span potential: 508 years). We found that in the heart of A. islandica the level of oxidatively damaged proteins did not change significantly up to 120 years of age. No significant aging-induced changes were observed in caspase-like and trypsin-like proteasome activity. Chymotrypsin-like proteasome activity showed a significant early-life decline, then it remained stable for up to 182 years. No significant relationship was observed between the extent of protein ubiquitination and age. In the heart of A. islandica, an early-life decline in expression of HSP90 and five mitochondrial electron transport chain complexes was observed. We found significant age-related increases in the expression of three cytokine-like mediators (interleukin-6, interleukin-1β, and tumor necrosis factor-α) in the heart of A. islandica. Collectively, in extremely long-lived molluscs, maintenance of protein homeostasis likely contributes to the preservation of cardiac function. Our data also support the concept that low-grade chronic inflammation in the cardiovascular system is a universal feature of the aging process, which is also manifest in invertebrates.

Keywords: Cardiac.; Extreme longevity; Invertebrate; Model system; Mollusc.

Figure 1.

The relationship between the protein carbonyl content (AU) of the heart tissue and age of Arctica islandica. Regression analysis: n = 18, F = 4.630; p = .046, r ² = .168.

Figure 2.

Proteasome activity (AU) in the hearts of Arctica islandica. Relationships between changes with age of chymotrypsin-like activity (A) (regression analysis: n = 19, F = 48.864, p = 0 < .001, r ² = .73), trypsin-like activity (B) (regression analysis: n = 19, F = 3.235, p = .089, r ² = .105), and caspase- like activity (C) (regression analysis: n = 19, F = 0.629, p = .438, r ² = .001).

Figure 3.

Protein ubiquitination was detected through Western blot analysis (A). Protein ubiquitination demonstrated no significant association with age (B; n = 19, F = 0.542, p = .471, r ² ≤ .001). No significant relationship between protein carbonylation and protein ubiquitination was also observed (C; n = 19, F = 0.0516, p = .823, r ² ≤ .001). There was also no significant relationships between protein ubiquitination and the three investigated proteasome activities (D; chymotrypsin-like: n = 19, F = 0.0491, p = .492, r ² ≤ .001); trypsin-like: n = 19, F = 1.467, p = .241, r ² = .240); caspase-like (n = 19, F = 2.288, p = .153, r ² ≤ .0687).

Figure 4.

Age-associated changes in heat shock expression in Arctica islandica across four age quartiles: 20–40 years old, 41–80 years old, 81–120 years old, and >120 years old. Fold changes in expression from the youngest quartile of HSP90 (A), HSP70 (B), HSP60 (C), and HSP40 (D) were assessed in the heart tissue across the four age quartiles. Data are mean ± SEM. Different letters indicate significant differences between the age quartiles in (A), as indicated by pairwise comparisons. No significant differences were detected in Figure 4B–D.

Figure 5.

Age-associated changes in the expression of different complexes of the five mitochondrial oxidative phosphorylation complexes in Arctica islandica across four age quartiles: 20–40 years old, 41–80 years old, 81–120 years old, and >120 years old. Fold changes in expression from the youngest quartile of complexes I (A), II (B), III (C), IV (D), and V (E) were assessed in the heart tissue across the four age quartiles. Data are mean ± SEM. Different letters indicate significant differences between the age quartiles, as indicated by pairwise comparisons.

Figure 6.

Age-associated changes in activity of cytokine-like molecules in Arctica islandica across four age quartiles: 20–40 years old, 41–80 years old, 81–120 years old, and >120 years old. Fold changes in concentration from the youngest quartile of interleukin-1β (A), interleukin-6 (B), and tumor necrosis factor-α (C) were assessed in the heart tissue across the four age quartiles. Data are mean ± SEM. Different letters indicate significant differences between the age quartiles, as indicated by pairwise comparisons, for example, in the case of IL-lβ, the third quartile is significantly elevated compared with the first two quartiles, but not the fourth.