SLAB51 Probiotic Formulation Activates SIRT1 Pathway Promoting Antioxidant and Neuroprotective Effects in an AD Mouse Model

Abstract

The gut-brain axis is a bidirectional communication network functionally linking the gut and the central nervous system (CNS). Based on this, the rational manipulation of intestinal microbiota represents a novel attractive therapeutic strategy for the treatment of CNS-associated disorders. In this study, we explored the properties of a probiotic formulation (namely SLAB51) in counteracting brain oxidative damages associated with Alzheimer's disease (AD). Specifically, transgenic AD mice (3xTg-AD) were treated with SLAB51 and the effects on protein oxidation, neuronal antioxidant defence and repair systems were monitored, with the particular focus on the role of SIRT1-related pathways. We demonstrated that SLAB51 markedly reduced oxidative stress in AD mice brain by activating SIRT1-dependent mechanisms, thus representing a promising therapeutic adjuvant in AD treatment.

Keywords: Alzheimer’s disease; Oxidation; Probiotics; SIRT1.

Fig. 1

Effect of SLAB51 on SIRT1 activity and expression. SIRT1 activity (a) and expression levels (b) measured in brain homogenates of SLAB51-treated and SLAB51-untreated wt (left) and AD (right) mice. The enzyme activity is expressed as fluorescent units (F.U.). The densitometric analyses obtained from five separate blots and representative immunoblots are shown. Equal protein loading was verified by using an anti-GAPDH antibody. The detection was performed with an ECL Western blotting analysis system. Statistical significance compared to untreated 8-week-old mice and age-matched mice is indicated with asterisks (*p < 0.05; **p < 0.01; ***p < 0.001) and hashtags (^#p < 0.05; ^##p < 0.01; ^###p < 0.001), respectively

Fig. 2

Effect of SLAB51 on p53. Acetylated p53 (a) and p53 (b) levels measured in brain homogenates of SLAB51-treated and SLAB51-untreated wt (left) and AD (right) mice. The densitometric analyses obtained from five separate blots and representative immunoblots are shown. Equal protein loading was verified by using an anti-GAPDH antibody. The detection was performed with an ECL Western blotting analysis system. Statistical significance compared to untreated 8-week-old mice and age-matched mice is indicated with asterisks (*p < 0.05; **p < 0.01; ***p < 0.001) and hashtags (^#p < 0.05; ^##p < 0.01; ^###p < 0.001), respectively. (c) Pairwise comparison of the effects of SLAB51 in Ac-p53/p53 ratios in wt and AD ageing mice. Statistical significance compared to age-matched mice is indicated with “^§” mark (^§p < 0.05; ^§§p < 0.01; ^§§§p < 0.001)

Fig. 3

Effect of SLAB51 on RARβ. Acetylated RARβ (a) and RARβ (b) levels measured in brain homogenates of SLAB51-treated and SLAB51-untreated wt (left) and AD (right) mice. The densitometric analyses obtained from five separate blots and representative immunoblots are shown. Equal protein loading was verified by using an anti-GAPDH antibody. The detection was performed with an ECL Western blotting analysis system. Statistical significance compared to untreated 8-week-old mice and age-matched mice is indicated with asterisks (*p < 0.05; **p < 0.01; ***p < 0.001) and hashtags (^#p < 0.05; ^##p < 0.01; ^###p < 0.001), respectively. c: Pairwise comparison of the effects of SLAB51 in Ac-RARβ/RARβ in wt and AD ageing mice. Statistical significance compared to age-matched mice is indicated with “^§” mark (^§p < 0.05; ^§§p < 0.01; ^§§§p < 0.001)

Fig. 4

Effect of SLAB51 on the activity of antioxidant enzymes. GST (a), GPx (b), SOD (c) and CAT (d) activities measured in brain homogenates of SLAB51-treated and SLAB51-untreated wt (left) and AD (right) mice (see “Materials and Methods” section for further details). Results are expressed as fluorescence units (F.U.). Statistical significance compared to untreated 8-week-old mice and age-matched mice is indicated with asterisks (*p < 0.05; **p < 0.01; ***p < 0.001) and hashtags (^#p < 0.05; ^##p < 0.01; ^###p < 0.001), respectively

Fig. 5

Effect of SLAB51 on protein and lipid oxidation. Protein carbonyls (a), 3-NT (b) and 4-HNE adduct (c) levels measured in brain homogenates of SLAB51-treated and SLAB51-untreated wt (left) and AD (right) mice. The densitometric analyses obtained from five separate blots and representative immunoblots are shown. Equal protein loading for 3-NT (b) and 4-HNE adducts (c) was verified by using an anti-GAPDH antibody. Ponceau staining has been used to check loading in oxyblot, as reported in the “Materials and Methods” section (a, staining not shown). The detection was performed with an ECL Western blotting analysis system. Molecular weight standards (6–205 kDa) were used for molar mass calibration (myosin 205 kDa, β-galactosidase 116 kDa, phosphorylase b 97 kDa, fructose-6-phosphate kinase 80 kDa, albumin 66 kDa, glutamic dehydrogenase 55 kDa, ovalbumin 45 kDa, carbonic anhydrase 30 kDa, trypsin inhibitor 21 kDa, lysozyme 14 kDa, aprotinin 6.5 kDa). Statistical significance compared to untreated 8-week-old mice and age-matched mice is indicated with asterisks (*p < 0.05; **p < 0.01; ***p < 0.001) and hashtags (^#p < 0.05; ^##p < 0.01; ^###p < 0.001), respectively

Fig. 6

Effect of SLAB51 on DNA oxidation and repair mechanisms. Cleaved PARP (a), OGG1 (b) and 8-oxodG (c) levels measured in brain homogenates of SLAB51-treated and SLAB51-untreated wt (left) and AD (right) mice. The densitometric analyses obtained from five separate blots and representative immunoblots are shown. Equal protein loading was verified by using an anti-GAPDH antibody. The detection was performed with an ECL Western blotting analysis system. Statistical significance compared to untreated 8-week-old mice and age-matched mice is indicated with asterisks (*p < 0.05; **p < 0.01; ***p < 0.001) and hashtags (^#p < 0.05; ^##p < 0.01; ^###p < 0.001), respectively