Microorganisms residing on the skin play a crucial role in maintaining both the integrity of the skin barrier and immune function. This study examined the effects of culture supernatants from canine-derived Bifidobacterium animalis subsp. lactis DS008 on canine keratinocytes in vitro. To induce cytokine production, canine progenitor epidermal keratinocytes (CPEK) were indirectly co-cultured with Malassezia pachydermatis using an insert well system to prevent direct cell-to-yeast contact, and CPEK were supplemented with 0.1%, 1%, and 10% of DS008 supernatants. mRNA expression levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-13, thymic stromal lymphopoietin (TSLP), IL-31, and keratin 10 were analyzed by real-time PCR. The protein concentrations of TSLP and IL-31 were measured by ELISA. Additionally, DS008 supernatants were applied to reconstructed canine epidermis (RCE) models exposed to lipopolysaccharide to evaluate changes in epidermal architecture. Treatment with DS008 supernatants showed significant reductions in mRNA expression of TNF-α, IL-13, TSLP, and IL-31, as well as decreased protein levels of TSLP and IL-31. Furthermore, keratin 10 mRNA expression was significantly increased, and RCE analysis demonstrated that DS008 supernatants ameliorated stratum corneum deformation. These findings suggest that postbiotics derived from canine-derived Bifidobacterium animalis subsp. lactis DS008 is a potential candidate with anti-inflammatory properties.

Consumption of oxidized foods or exposure of skin to ultraviolet (UV) can produce reactive oxygen species (ROS) that increase oxidative stresses that can lead to skin aging and melanogenesis. Hydrolyzing proteins like ovalbumin (OA) can significantly increase their bioactivities. In this study, OA was hydrolyzed using Alcalase 2.4 L FG, Multifect PR 14 L, and Papain T100 MG, and the antioxidant and melanogenesis inhibitory activities of the hydrolysates were determined using B16F10 melanoma cells. All OA hydrolysates (OAH) showed higher antioxidant activities than the natural OA. The OAH prepared with Multifect PR 14 L (OAMF) exhibited the highest antioxidant activities and significantly inhibited melanin production and tyrosinase activity in the stimulated B16F10 cells using α-melanocyte-stimulating hormone. The DOPA staining confirmed the melanogenesis inhibitory (melanin formation and dendrite development) effects of OAMF. The OAMF (100, 200, and 400 µg/mL) treatment downregulated the mRNA expression of microphthalmia-associated transcription factor (MITF) and melanogenic enzymes [tyrosinase, tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2 (TRP-2)] dose-dependently. Therefore, OAMF can help reduce oxidative stress in humans when consumed and can be used as an anti-aging and skin-lightening agent in the cosmetic industry.

Alterations in the ceramide (CER) profile have been associated with atopic dermatitis in dogs; however, the specific effects of CER subclasses on canine keratinocytes remain unclear. This study aimed to optimize a CER complex and evaluate its effects on cytokine expression, CER synthesis, and skin barrier formation using canine epidermal keratinocyte progenitor (CPEK) cells and a reconstructed canine epidermis (RCE) model. Among various CER combinations tested, only the mixture of CER [NS] and [EOP] significantly reduced proinflammatory cytokine mRNA levels in Staphylococcus pseudintermedius–stimulated CPEK cells. Further optimization revealed that a 4:1 ratio of CER [NS] to [EOP] (cCER complex) markedly decreased CCL17 and CCL22 mRNA expression while upregulating keratin 10, ceramide synthase 3 (CERS3), and ceramide synthase 4, as well as enzymes involved in both de novo and salvage CER biosynthesis pathways. In the RCE model, cCER administration improved stratum corneum organization and increased the expression of loricrin, CERS3, and CER. In vivo application of cCER in dogs accelerated skin barrier repair and improved hair condition. These findings suggest that a CER [NS]/[EOP] mixture represents a promising therapeutic option with anti-inflammatory and skin barrier-enhancing effects for canine atopic dermatitis.