Human α-Defensin 51-9 and Human β-Defensin 2 Improve Metabolic Parameters and Gut Barrier Function in Mice Fed a Western-Style Diet

Toll-like receptor 2 activation induces C-C motif chemokine ligand 5 production in canine keratinocytes

BACKGROUND

Toll-like receptor 2 (TLR2) in keratinocytes can be activated by Staphylococcus spp. that are frequently detected on the skin of dogs with atopic dermatitis (AD). C-C motif chemokine ligand 5 (CCL5) produced by keratinocytes has been considered to be involved in the pathogenesis of canine AD (cAD). However, whether TLR2 activation induces CCL5 production in canine keratinocytes remains unclear.

HYPOTHESIS/OBJECTIVES

To elucidate the effect of TLR2 agonists on CCL5 production in canine keratinocytes, possible synergy with interferon (IFN)-γ, interleukin (IL)-13 or IL-4 and underlying mechanisms.

MATERIALS AND METHODS

Canine progenitor epidermal keratinocyte (CPEK) cells were stimulated with TLR2 agonists with or without inhibitors of the TLR2 signalling pathway or IFN-γ, a T-helper (Th)1-type cytokine and/or IL-13 or IL-4, a Th2-type cytokine. CCL5 protein concentrations in the culture supernatant were measured by enzyme-linked immunosorbent assay. Additionally, TLR2 mRNA expression was measured by real-time PCR in CPEK cells stimulated with IFN-γ.

RESULTS

TLR2 agonists increased CCL5 production in CPEK cells. Inhibitors of the TLR2 signalling pathway suppressed CCL5 production. IFN-γ, but not IL-13 or IL-4, synergistically enhanced TLR2 agonist-induced CCL5 production. IFN-γ partially increased TLR2 mRNA expression in CPEK cells.

CONCLUSIONS AND CLINICAL RELEVANCE

TLR2 activation by Staphylococcus spp. may produce CCL5 in canine keratinocytes, thereby recruiting immune cells into the skin of dogs with AD. During the Th1-activated chronic phase of cAD, where TLR2 expression may be partially upregulated, Staphylococcus spp. may exacerbate skin inflammation. Further studies are warranted to determine the clinical significance and mechanisms of skin bacteria-mediated CCL5 production in keratinocytes.

Systemic Factors Affecting Human Beta-Defensins in Oral Cavity

Human beta-defensins are host defense peptides with broad antimicrobial and inflammatory functions. In the oral cavity, these peptides are produced mainly by the keratinocytes of the epithelium; however, fibroblasts, monocytes, and macrophages also contribute to oral human beta-defensin expressions. The resident and immune cells of the oral cavity come into contact with various microbe-associated molecular patterns continuously and simultaneously. The overall antimicrobial cellular response is highly influenced by local and environmental factors. Recent studies have produced evidence showing that not only systemic chronic diseases but also systemic factors like hyperglycemia, pregnancy, the long-term use of certain vitamins, and aging can modulate oral cellular antimicrobial responses against microbial challenges. Therefore, the aim of this narrative review is to discuss the role of systemic factors on oral human beta-defensin expressions.

The relevance of intestinal barrier dysfunction, antimicrobial proteins and bacterial endotoxin in metabolic dysfunction-associated steatotic liver disease

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a leading cause of end-stage liver disease associated with increased mortality and cardiovascular disease. Obesity and diabetes are the most important risk factors of MASLD. It is well-established that obesity-associated insulin resistance leads to a situation of tissue lipotoxicity characterized by an accumulation of excess fat in non-fat tissues such as the liver, promoting the development of MASLD, and its progression into metabolic dysfunction-associated steatohepatitis.

METHODS

Here, we aimed to review the impact of disrupted intestinal permeability, antimicrobial proteins and bacterial endotoxin in the development and progression of MASLD.

RESULTS AND CONCLUSION

Recent studies demonstrated that obesity- and obesogenic diets-associated alterations of intestinal microbiota along with the disruption of intestinal barrier integrity, the alteration in antimicrobial proteins and, in consequence, an enhanced translocation of bacterial endotoxin into bloodstream might contribute to this pathological process through to impacting liver metabolism and inflammation.

Host defense peptides human β defensin 2 and LL-37 ameliorate murine necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of preterm infant morbidity and mortality. Treatment for NEC is limited and non-targeted, which makes new treatment and prevention strategies critical. Host defense peptides (HDPs) are essential components of the innate immune system and have multifactorial mechanisms in host defense. LL-37 and hBD2 are two HDPs that have been shown in prior literature to protect from neonatal sepsis-induced mortality or adult inflammatory bowel disease, respectively. Therefore, this article sought to understand if these two HDPs could influence NEC severity in murine preclinical models. NEC was induced in P14-16 C57Bl/6 mice and HDPs were provided as a pretreatment or treatment. Both LL-37 and hBD2 resulted in decreased NEC injury scores as a treatment and hBD2 as a pretreatment. Our data suggest LL-37 functions through antimicrobial properties, while hBD2 functions through decreases in inflammation and improvement of intestinal barrier integrity.

Loss of Paneth cells dysregulates gut ILC subsets and enhances weight gain response to high fat diet in a mouse model

Obesity has been associated with dysbiosis, but innate mechanisms linking intestinal epithelial cell subsets and obesity remain poorly understood. Using mice lacking Paneth cells (Sox9 ΔIEC mice), small intestinal epithelial cells specialized in the production of antimicrobial products and cytokines, we show that dysbiosis alone does not induce obesity or metabolic disorders. Loss of Paneth cells reduced ILC3 and increased ILC2 numbers in the intestinal lamina propria. High-fat diet (HFD) induced higher weight gain and more severe metabolic disorders in Sox9 ΔIEC mice. Further, HFD enhances the number of ILC1 in the intestinal lamina propria of Sox9 ΔIEC mice and increases intestinal permeability and the accumulation of immune cells (inflammatory macrophages and T cells, and B cells) in abdominal fat tissues of obese Sox9 ΔIEC . Transplantation of fecal materials from Sox9 ΔIEC mice in germ-free mice before HFD further confirmed the regulatory role of Paneth cells for gut ILC subsets and the development of obesity.