Aging exacerbates cardiac dysfunction and mortality in sepsis through enhancing TLR2 activity

Figures

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  Figure 1. Old septic mice have high mortality. Male young adult WT mice (4–6 month old) and old WT mice (18–20 month old) were subjected to cecal ligation and puncture (CLP; 1 puncture with a 27G needle). Half of the old WT mice died during the 4-day period following CLP while none of the young adult mice died in the same period. Old mice mainly die in the first 2 days. n = 12 in each group; *P < 0.05 vs. WT young adult mice.

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  Figure 2. Sepsis results in greater and sustained cardiac dysfunction in old mice. Young adult and old mice were subject to CLP or sham procedure. Left ventricular (LV) function was analyzed using microcatheter at 1, 2, and 4 days following CLP. Representative pressure-volume loops show that sepsis resulted in more severe cardiac dysfunction in old mice compared to young adult mice. While cardiac function in young adult mice recovered to a level comparable to the sham control level 4 days after CLP, it remained notably lower than the corresponding sham control level in old mice after 4 days.

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  Figure 3. TLR2 level is elevated in multiple organs of old mice. Immunoblotting and densitometric analysis revealed higher levels of TLR2 in the heart, liver and kidney of old mice in comparison to young adult mice. Data are presented as box-and-whiskers plots where the upper and lower borders of the box represent the upper and lower quartiles; the horizontal line inside the box represents the median; the upper and lower whiskers represent the maximum and minimum values of nonoutliers; and the + sign represents the mean, n = 4–5; *P < 0.05 vs. young adult.

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  Figure 4. TLR2 KO results in a greater reduction of the inflammatory activity during sepsis in old mice. WT young adult and old mice, as well as TLR2 KO young adult and old mice were subjected to CLP or sham procedure. TNF-α, IL-1β, IL-6 and MCP-1 in the myocardium (A) and plasma (B) were analyzed using ELISA. Old WT mice had a greater increase in the levels of inflammatory cytokines at all of the time points following CLP. TLR2 KO attenuated the inflammatory response to sepsis in both young adult and old septic mice and markedly diminished the age-related difference in cytokine levels following CLP. Data are presented as box-and-whiskers plots where the upper and lower borders of the box represent the upper and lower quartiles; the horizontal line inside the box represents the median; the upper and lower whiskers represent the maximum and minimum values of nonoutliers; and the + sign represents the mean, *P < 0.05 vs. corresponding sham; #P < 0.05 vs. corresponding young adult of the same strain; †P < 0.05 vs. WT of the same age. n = 6 in each group.

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  Figure 5. TLR2 KO decreases mortality rate during sepsis in old mice. WT old mice and TLR2 KO old mice were subjected to CLP. Mortality was reduced to 25% during the 4-day period in TLR2 KO old mice compared to WT old mice with a 50% mortality. *P < 0.05 vs. WT old, n = 12 in each group.

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  Figure 6. Aging exaggerates the inflammatory activity and worsens cardiac dysfunction caused by TLR2 stimulation. Young adult and old WT mice were treated with the specific TLR2 agonist Pam3CSK4 (2.5 µg/ g, iv) or normal saline. TNF-α, IL-1β, IL-6 and MCP-1 in the myocardium were analyzed using ELISA, and cardiac function was assessed using microcatheter 1, 2 and 4 days after treatment. (A). Myocardial levels of inflammatory cytokines increased in both young adult and old mice at 1 and 2 days after administration of TLR2 agonist, and old mice displayed a greater increase in comparison to young adult mice. (B) Ejection fraction and cardiac output decreased in young adult and old mice at 1 and 2 days after administration of TLR2 agonist in comparison to control levels, and old mice had worse cardiac function in comparison to young adult mice. Data are presented as box-and-whiskers plots where the upper and lower borders of the box represent the upper and lower quartiles; the horizontal line inside the box represents the median; the upper and lower whiskers represent the maximum and minimum values of nonoutliers; and the + sign represents the mean, *P < 0.05 vs. corresponding control, #P <…