Cell type-specific differences in β-glucan recognition and signalling in porcine innate immune cells

Euglena gracilis paramylon activates human lymphocytes by upregulating pro-inflammatory factors

The aim of this study was to verify the activation details and products of human lymphomonocytes, stimulated by different β-glucans, that is Euglena paramylon, MacroGard^®, and lipopolysaccharide. We investigated the gene expression of inflammation-related cytokines and mediators, transactivation of relevant transcription factors, and phagocytosis role in cell-glucan interactions, by means of RT-PCR, immunocytochemistry, and colorimetric assay. Our results show that sonicated and alkalized paramylon upregulates pro-inflammatory factors (NO, TNF-α, IL-6, and COX-2) in lymphomonocytes. A clear demonstration of this upregulation is the increased transactivation of NF-kB visualized by immunofluorescence microscopy. Phagocytosis assay showed that internalization is not a mandatory step for signaling cascade to be triggered, since immune activity is not present in the lymphomonocytes that have internalized paramylon granules and particulate MacroGard^®. Moreover, the response of Euglena β-glucan-activated lymphomonocytes is much greater than that induced by commercially used β-glucans such as MacroGard^®. Our in vitro results indicate that linear fibrous Euglena β-glucan, obtained by sonication and alkaline treatment can act as safe and effective coadjutant of the innate immune system response.

Polymorphisms of the immune-modulating receptor dectin-1 in pigs: their functional influence and distribution in pig populations

Dectin-1, a C-type lectin receptor that recognizes fungal β-glucans, is involved in antifungal immunity and the regulation of intestinal immune homeostasis. Dectin-1 is involved in both synthesis and maturation of interleukin-1β, a key pro-inflammatory cytokine in immunity. Here, we assessed the genetic diversity in the gene encoding dectin-1 (CLEC7A) within various pig populations and examined the influence of these polymorphisms on the two different signaling pathways after ligand recognition. An amino-acid polymorphism located in the carbohydrate-recognition domain, leucine to serine at position 138 (L138S), which occurred exclusively in Japanese wild boars at low frequency, significantly increased NF-κB induction but not caspase-8 activity after stimulation with zymosan. In contrast, other amino-acid polymorphisms present at comparatively high frequency in commercial pig populations had little influence on ligand recognition. These results suggest that functionally neutral polymorphisms in dectin-1 are widespread in pig populations.

Muscle wound healing in rainbow trout (Oncorhynchus mykiss)

We followed the progression of healing of deep excisional biopsy punch wounds over the course of 365 days in rainbow trout (Oncorhynchus mykiss) by monitoring visual wound healing and gene expression in the healing muscle at regular intervals (1, 3, 7, 14, 38 and 100 days post-wounding). In addition, we performed muscle texture analysis one year after wound infliction. The selected genes have all previously been investigated in relation to vertebrate wound healing, but only few specifically in fish. The selected genes were interleukin (IL)-1β, IL-6, transforming growth factor (TGF)-β1 and -β3, matrix metalloproteinase (MMP) -9 and -13, inducible nitric oxide synthase (iNOS), fibronectin (FN), tenascin-C (TN-C), prolyl 4-hydroxylase α1-chain (P4Hα1), lysyl oxidase (LOX), collagen type I α1-chain (ColIα1), CD41 and CD163. Wound healing progressed slowly in the presented study, which is at least partially due to the low temperature of about 8.5 °C during the first 100 days. The inflammation phase lasted more than 14 days, and the genes relating to production and remodeling of new extracellular matrix (ECM) exhibited a delayed but prolonged upregulation starting 1-2 weeks post-wounding and lasting until at least 100 days post-wounding. The gene expression patterns and histology reveal limited capacity for muscle regeneration in rainbow trout, and muscle texture analyses one year after wound infliction confirm that wounds heal with fibrosis. At 100 dpw epidermis had fully regenerated, and dermis partially regenerated. Scales had not regenerated even after one year. CD163 is a marker of "wound healing"-type M2c macrophages in mammals. M2 macrophage markers are as yet poorly described in fish. The pattern of CD163 expression in the present study is consistent with the expected timing of presence of M2c macrophages in the wound. CD163 may thus potentially prove a valuable marker of M2 macrophages - or a subset hereof - in fish. We subjected a group of fish to bathing in an immunomodulatory β-glucan product during wound healing, but found this to have very limited effect on wound healing in contrast to a previously published study on common carp.

Dietary fibre and crude protein: impact on gastrointestinal microbial fermentation characteristics and host response

The role of the gastrointestinal tract microbiota in animal health and nutrition has become the subject of intensive research. Carbohydrates and crude protein are major components of swine diets and numerous studies have been performed looking at the effect of inclusion of dietary fibre with possible functional properties. In recent years, our understanding of the diversity and functionality of the gastrointestinal tract microbiota has increased further enabling the possibility for their targeted modulation. However, favouring potential beneficial bacteria, inhibiting possible pathogens or promotion of the formation of desired metabolites, is complex and underlies many factors and uncertainties. Approaches targeting this complex ecosystem (and discussed in this review) include the utilisation of fermentable carbohydrates such as resistant starch, cereal 1–3/1–4 β-glucans, arabinoxylans, inulin or other sources from legumes and industrial by-products. In addition, strategies regarding protein level and the protein : carbohydrate ratio are discussed briefly. Results are both promising and sometimes rather disillusioning considering the dietary concentrations needed to show biologically relevant effects. Deriving recommendations for an optimal inclusion rate of dietary fibre for weaning, growing pigs and sows and maximum levels for dietary crude protein may be one of the main challenges in the near future in the swine industry.