OPN/miRNA-181A axis as a potential marker of inflammation during aging in male wistar rats of different age ranges.

BACKGROUND-AIM Aging is caused by the dysfunction of different physiological and metabolic processes and characterized by a low- grade systemic inflammation. The Osteopontin (OPN), an extracellular matrix glycoprotein, plays an important role as cytokine during inflammation and recently it was identified as a hepatic damage marker. An important role during aging was also associated with a different modulation of miRNAs due to their ability to modulate the expression of important pro-inflammatory molecules. Aim was to evaluate, in liver tissue of rats of different age ranges, the expression variations of OPN and of its modulator miRNA-181a. TNF-?, PTX -3, IL-10 mRNA was also evaluated. METHODS Male Wistar rats were studied: A (n=6; age=248+0.00 days-young), B (n=13; age=413.8+8.20 days-adult), C (n=10; age=597.6+10.3 days-old). Total RNA and miRNA were simultaneously extracted from liver tissue samples and analyzed by Real-Time PCR. Histological analysis of the hepatic tissues and ultrasound evaluation were performed. RESULTS The OPN mRNA resulted lower in C (0.65+0.12) with respect to A (1.07+0.12) and B (1.32+0.26; p=0.03 B vs. C) while the miRNA-181a expression resulted significantly increased as a function of age (A=0.72+0.29; B=1.09+0.08; C=1.33+0.24; p=0.03 A vs. B; p=0.02 A vs. C). IL-10 mRNA expression resulted significantly higher in B with respect to A and C (A=0.24+0.43; B=0.43+0.05; C=0.29+0.53; p=0.04 B vs. A; p=0.03 B vs. C). TNF-?expression resulted significantly lower in C (A=1.36+0.25; B=1.81+0.27; C=1.07+0.14; p=0.04 B vs. C) while PTX-3 mRNA expression resulted similar in all groups (A=0.85+0.16; B=0.74+0.21; C=0.81+0.15). Significative correlations were observed between OPN vs IL-10 (r=0.44, p=0.02) and between OPN and TNF-? (r=0.50, p=0.009). The hepatic ultrasound analysis revealed areas of hyperechogenicity distributed as a function of age with absence of neoplastic formations as also confirmed by the echographic and hystological analysis. The OPN mRNA resulted lower in C (0.65+0.12) with respect to A (1.07+0.12) and B (1.32+0.26; p=0.03 B vs. C) while the miRNA-181a expression resulted significantly increased as a function of age (A=0.72+0.29; B=1.09+0.08; C=1.33+0.24; p=0.03 A vs. B; p=0.02 A vs. C). IL-10 mRNA expression resulted significantly higher in B with respect to A and C (A=0.24+0.43; B=0.43+0.05; C=0.29+0.53; p=0.04 B vs. A; p=0.03 B vs. C). TNF-?expressionresulted significantly lower in C (A=1.36+0.25; B=1.81+0.27; C=1.07+0.14; p=0.04 B vs. C) while PTX-3 mRNA expression resulted similar in all groups (A=0.85+0.16; B=0.74+0.21; C=0.81+0.15). Significative correlations were observed between OPN vs IL-10 (r=0.44, p=0.02) and between OPN and TNF-? (r=0.50, p=0.009). The hepatic ultrasound analysis revealed areas of hyperechogenicity distributed as a function of age with absence of neoplastic formations as also confirmed by the echographic and hystological analysis. CONCLUSIONS The results showed an indirect back regulation of the OPN miRNA-181a mediated, underlying their role as potential successful markers of inflamm-aging. Data on expression of pro and anti-inflammatory cytokine support the hypothesis that IL-10 is involved in a "healthy aging" playing an important role inhibiting the activation and function of lymphocytes T, monocytes and macrophages and checking the innate immunity. Although further studies are needed this work provides a valid starting point to better understand the physiopathological changes occurring during aging process identifying in the OPN/miRNA-181a axis a potential marker of inflammation during aging.