Effects of Bacterial Lysates and Metabolites on Collagen Homeostasis in TNF-α-Challenged Human Dermal Fibroblasts

Abstract

During skin aging, the production of extracellular matrix (ECM) proteins, such as type I collagen, decreases and the synthesis of ECM-degrading matrix metalloproteinases (MMPs) rises, leading to an imbalance in homeostasis and to wrinkle formation. In this study, we examined the effects of bacterial lysates and metabolites from three bifidobacteria and five lactobacilli on collagen homeostasis in human dermal fibroblasts during challenge with tumor necrosis factor alpha (TNF-α), modeling an inflammatory condition that damages the skin's structure. Antiaging properties were measured, based on fibroblast cell viability and confluence, amount of type I pro-collagen, ratio of MMP-1 to type I pro-collagen, cytokines, and growth factors. The TNF-α challenge increased the MMP-1/type I pro-collagen ratio and levels of proinflammatory cytokines, as expected. With the probiotics, differences were clearly dependent on bacterial species, strain, and form. In general, the lysates elicited less pronounced responses in the biomarkers. Of all strains, the Bifidobacterium animalis ssp. lactis strains Bl-04 and B420 best maintained type I pro-collagen production and the MMP-1/collagen type I ratio under no-challenge and challenge conditions. Metabolites that were produced by bifidobacteria, but not their lysates, reduced several proinflammatory cytokines (IL-6, IL-8, and TNF-α) during the challenge, whereas those from lactobacilli did not. These results indicate that B. animalis ssp. lactis-produced metabolites, especially those of strains Bl-04 and B420, could support collagen homeostasis in the skin.

Keywords: collagen; cytokines; human dermal fibroblast; matrix metalloproteinase; postbiotic; probiotic; skin aging.

Figure 1

Principal component analysis of the experimental dataset with the first two principal components. Unchallenged samples are indicated by open boxes, and challenged samples are indicated by filled boxes. Different colors refer to different sample types: black—controls, red—lysates and blue—metabolites. Comp1: principal component 1; comp2: principal component 2; ctrl: control.

Figure 2

Relative fold-changes in parameters compared with the respective cell passage controls under unchallenged and TNF-α-challenged conditions in HDFs treated with bacterial lysates or metabolites. The controls were medium for the no-challenge data and TNF-α for the challenge data. TGF-β1 was used as a positive control for type I pro-collagen production. Statistically significant (p < 0.05) changes versus the respective controls are denoted in bold (detailed p-values of the fold-changes can be found in Supplementary Figure S1). Without the challenge, there were no detectable amounts of IL-1α or TNF-α in the samples; thus, the effect sizes are not included in the figure. Ctrl: control.

Figure 3

Effects of bacterial lysates and metabolites on (a) type I pro-collagen and (b) MMP-1/type I pro-collagen ratio in unchallenged and TNF-α-challenged HDF cultures. In (a), the values are relative to controls, normalized to 100%. The average of the control levels (medium controls with no challenge and TNF-α controls with challenge, from two datasets of HDF passages) is shown as a black dashed line, and the TGF-β1 positive control for type I pro-collagen production is shown as a red dashed line. The bar graphs show the mean ± standard error (SE), and statistically significant differences between samples and controls (sample compared with the respective HDF passage control) are denoted by asterisks (*) as follows: * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001.