Sex Differences in the Inflammatory Profile in the Brain of Young and Aged Mice

Abstract

Neurodegenerative diseases are a leading cause of death worldwide with no cures identified. Thus, there is a critical need for preventative measures and treatments as the number of patients is expected to increase. Many neurodegenerative diseases have sex-biased prevalence, indicating a need to examine sex differences when investigating prevention and treatment strategies. Inflammation is a key contributor to many neurodegenerative diseases and is a promising target for prevention since inflammation increases with age, which is known as inflammaging. Here, we analyzed the protein expression levels of cytokines, chemokines, and inflammasome signaling proteins in the cortex of young and aged male and female mice. Our results show an increase in caspase-1, interleukin (IL)-1β, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and ASC specks in females compared to males. Additionally, there was an increase in IL-1α, VEGF-A, CCL3, CXCL1, CCL4, CCL17, and CCL22 in aging females and an increase in IL-8, IL-17a, IL-7, LT-α, and CCL22 in aging males. IL-12/IL-23p40, CCL13, and IL-10 were increased in females compared to males but not with age. These results indicate that there are sex differences in cortical inflammaging and provide potential targets to attenuate inflammation to prevent the development of neurodegenerative disease.

Keywords: ASC; IL-1β; brain; caspase-1; chemokines; cytokines; inflammaging; inflammasome; sex differences.

Figure 1

Inflammasome proteins are increased in the cortex of female mice. Mice were sacrificed at young (3 months) and aged (18 months) timepoints. Cortical protein lysates from young and aged males and females were immunoblotted for inflammasome proteins. (A) Representative immunoblots for young females vs. aged females and quantification of (B) ASC, (C) caspase-1, and (D) IL-1β. (E) Representative immunoblots for young females vs. young males and quantification of (F) ASC, (G) caspase-1, and (H) IL-1β. (I) Representative immunoblots for aged females vs. aged males and quantification of (J) ASC, (K) caspase-1, and (L) IL-1β. Data presented as mean +/− SEM. YF: young female, YM: young male, AF: aged female, AM: aged male. N = 6 to 7 per group. β-actin was used as a protein loading control and internal standard.

Figure 2

ASC specks are increased in the cortex of aged female mice. Cortical protein lysates from young (3 months) and aged (18 months) male and female mice underwent partial purification of the pyroptosome. (A) Representative immunoblot of cortical lysate of young and aged male and female mice blotted for ASC. (B) Quantification of ASC specks. Data presented as mean +/− SEM. YF: young female, YM: young male, AF: aged female, AM: aged male. N = 4 to 5 per group.

Figure 3

Sex and age differences in cytokine levels in the cortex of mice. Cortical protein lysates from young (3 months) and aged (18 months) male and female mice were analyzed for cytokine levels using multiplex assays. The cytokines that show a significant increase in aging are (A) IL-1α, (B) IL-8, (C) IL-17a, (D) IL-7, (E) LT-α, and (F) VEGF-A. Data presented as mean +/− SEM. N = 5 to 7 per group.

Figure 4

Sex and age differences in chemokine levels in the cortex of mice. Cortical protein lysates from young (3 months) and aged (18 months) male and female mice were analyzed for chemokine levels using multiplex assays. The chemokines that show a significant increase in aging are (A) CCL3, (B) CXCL1, (C) CCL4, (D) CCL17 and (E) CCL22. Data presented as mean +/− SEM. N = 5 to 12 per group.

Figure 5

Sex differences in cytokines and chemokines in the cortex of mice. Cortical protein lysates from young (3 months) and aged (18 months) male and female mice were analyzed for cytokine and chemokine levels using multiplex assays. The cytokines and chemokines that show a significant difference between sexes regardless of age are (A) IL-12/IL-23p40, (B) CCL13, and (C) IL-10. Data presented as mean +/− SEM. N = 6 to 12 per group.