Mueller polarimetric imaging as a tool for detecting the effect of non-thermal plasma treatment on the skin

Non-thermal plasma (NTP) is a promising technique studied for several medical applications such as wound healing or tumor reduction. The detection of microstructural variations in the skin is currently performed by histological methods, which are time-consuming and invasive. This study aims to show that full-field Mueller polarimetric imaging is suitable for fast and without-contact detection of skin microstructure modifications induced by plasma treatment. Defrosted pig skin is treated by NTP and analyzed by MPI within 30 minutes. NTP is shown to modify the linear phase retardance and the total depolarization. The tissue modifications are inhomogeneous and present distinct features at the center and the fringes of the plasma-treated area. According to control groups, tissue alterations are primarily caused by the local heating concomitant to plasma-skin interaction.

Cold Atmospheric Plasma Promotes Killing of Staphylococcus aureus by Macrophages

Macrophages are important immune cells that are involved in the elimination of microbial pathogens. Following host invasion, macrophages are recruited to the site of infection, where they launch antimicrobial defense mechanisms. Effective microbial clearance by macrophages depends on phagocytosis and phagolysosomal killing mediated by oxidative burst, acidification, and degradative enzymes. However, some pathogenic microorganisms, including some drug-resistant bacteria, have evolved sophisticated mechanisms to prevent phagocytosis or escape intracellular degradation. Cold atmospheric plasma (CAP) is an emerging technology with promising bactericidal effects. Here, we investigated the effect of CAP on Staphylococcus aureus phagocytosis by RAW 264.7 macrophage-like cells. We demonstrate that CAP treatment increases intracellular concentrations of reactive oxygen species (ROS) and nitric oxide and promotes the elimination of both antibiotic-sensitive and antibiotic-resistant S. aureus by RAW 264.7 cells. This effect was inhibited by antioxidants indicating that the bactericidal effect of CAP was mediated by oxidative killing of intracellular bacteria. Furthermore, we show that CAP promotes the association of S. aureus to lysosomal-associated membrane protein 1 (LAMP-1)-positive phagosomes, in which bacteria are exposed to low pH and cathepsin D hydrolase. Taken together, our results provide the first evidence that CAP activates defense mechanisms of macrophages, ultimately leading to bacterial elimination. IMPORTANCE Staphylococcus aureus is the most frequent cause of skin and soft tissue infections. Treatment failures are increasingly common due to antibiotic resistance and the emergence of resistant strains. Macrophages participate in the first line of immune defense and are critical for coordinated defense against pathogenic bacteria. However, S. aureus has evolved sophisticated mechanisms to escape macrophage killing. In the quest to identify novel antimicrobial therapeutic approaches, we investigated the activity of cold atmospheric plasma (CAP) on macrophages infected with S. aureus. Here, we show that CAP treatment promotes macrophage ability to eliminate internalized bacteria. Importantly, CAP could trigger killing of both antibiotic-sensitive and antibiotic-resistant strains of S. aureus. While CAP did not affect the internalization capacity of macrophages, it increased oxidative-dependent bactericidal activity and promoted the formation of degradative phagosomes. Our study shows that CAP has beneficial effects on macrophage defense mechanisms and may potentially be useful in adjuvant antimicrobial therapies.

A Murine Model of a Burn Wound Reconstructed with an Allogeneic Skin Graft

Trivial superficial wounds heal without complications by primary intention. Deep wounds, such as full thickness burns, heal by secondary intention and require surgical debridement and skin grafting. Successful integration of the donor graft into a recipient wound bed depends on timely recruitment of immune cells, robust angiogenic response and new extracellular matrix formation. The development of novel therapeutic agents, which target some key processes involved in wound healing, are hindered by the lack of reliable preclinical models with optimized objective assessment of wound closure. Here, we describe an inexpensive and reproducible model of experimental full thickness burn wound reconstructed with an allogeneic skin graft. The wound is induced on the dorsum surface of anaesthetized inbred wild type mice from the BALB/C and SKH1-Hrhr backgrounds. The burn is produced using a brass template measuring 10 mm in diameter, which is preheated to 80 °C and delivered at a constant pressure for 20 s. Burn eschar is excised 24 hours after the injury and replaced with a full thickness graft harvested from the tail of a genetically similar donor mouse. No specialized equipment is required for the procedure and surgical techniques are straightforward to follow. The method may be effortlessly implemented and reproduced in most research settings. Certain limitations are associated with the model. Due to technical difficulties, the harvest of thinner split thickness skin grafts is not possible. The surgical method we describe here allows for the reconstruction of burn wounds using full thickness skin grafts. It may be used to carry out preclinical therapeutic testing.

Differential effect of insulin-like growth factor I on in vitro gonadotropin (I and II) and growth hormone secretions in rainbow trout (Oncorhynchus mykiss) at different stages of the reproductive cycle

The short-term effect of insulin-like growth factor I (IGF-I) on GTH I (FSH-like), GTH II (LH-like), and GH production by cultured rainbow trout pituitary cells was studied in immature fish of both sexes, at early gametogenesis and in spermiating and periovulatory animals. IGF-I had no effect on basal GTH I and GTH II release, whereas it always inhibited basal GH, showing decreasing intensity with the gonad maturation. In absence of IGF-I, GTH I and GTH II cells were always responsive to GnRH, whereas no response was observed for GH cells whatever the sexual stage. The action of IGF-I on the sensitivity to GnRH differs between GTH and GH cells. The former requires a coincubation with IGF-I (10(-6) M)/GnRH to show an increase in sensitivity, independent of the sexual stage. To be responsive to GnRH, the GH cells require longer exposure to IGF-I, the efficiency of which decreases with gonad maturation. The action of IGF-I (10(-6) M) on GTH cell sensitivity to GnRH does not seem to be related to a mitogenic effect or to an improvement in cell survival. It seems to be IGF-I specific, not passing via the insulin receptor. Certain hypotheses on the putative role of IGF-I and GnRH as a link between growth and puberty are suggested.

Gonadotropin-I and -II subunit gene expression of male striped bass (Morone saxatilis) after gonadotropin-releasing hormone analogue injection: quantitation using an optimized ribonuclease protection assay

In fish, both gonadotropin (GtH)-I and -II are involved in the spermatogenic process, but the differential regulation of these hormones by GnRH is still poorly understood. To gain further insight into the GnRH regulation of GtH-I and -II gene expression in the male striped bass, we have developed and optimized a ribonuclease protection assay for the simultaneous measurement of all GtH subunit mRNAs in a single pituitary gland. The RNA extraction protocol enables the determination of GtH protein content in the same sample, thus enhancing the power of the method. Maturing striped bass males were injected intramuscularly with [D-Ala6,Pro9Net]-LHRH (GnRHa) and sampled at 6 and 24 h postinjection. The mRNA levels of the alpha subunit and GtH-IIbeta increased after 6 h (4- and 6-fold, respectively), while the GtH-Ibeta mRNA levels increased only 2-fold after 24 h. Interestingly, GnRHa stimulation caused a significant increase in beta-actin mRNA levels. GnRHa treatment also resulted in a 2-fold decrease in pituitary GtH-II content, associated with a dramatic increase of plasma GtH-II levels from undetectable levels (< 0.2 ng/ml) to 13+/-2 ng/ml after 6 h. These results demonstrate that both GtH-Ibeta and -Ilbeta are expressed during striped bass spermatogenesis and that the two genes are subjected to differential regulation by GnRHa.

Role of IGF-I in the control of GH secretion in rainbow trout (Oncorhynchus mykiss)

To study the role of IGF-I on GH secretion, we looked firstly for IGF-I binding sites in the central nervous system. IGF-I presents a single class of binding sites on brain membranes and pituitary extracts. Their affinity constants (Ka) were 11.44 +/- 4.66 and 4.42 +/- 1.37 x 10(9) M-1, respectively and their capacity (Bmax) were 119.83 +/- 46.21 and 73.65 +/- 20.87 fmoles/mg, respectively. In a second step IGF-I and bGH action on GH release was tested in vitro and in vivo. IGF-I inhibited GH release by pituitary cell cultures while bGH did not, suggesting direct action of IGF at the pituitary level and indirect action of GH, possibly mediated by IGF-I. IGF-I injected into catheterization fish induced a rapid inhibition of GH release, while bGH induced a delayed one. This timing supports a direct effect of IGF-I on GH release and the indirect effect of bGH. So peripheral IGF-I can play a role on GH secretion, perhaps as a mediator of GH action. This could explain the delayed fluctuation of GH and IGF-I plasma levels previously observed. This strong relationship between plasma IGF and GH secretion in trout seems to be different from that in mammals in which systemic IGF does not seem to play a predominant role in regulating GH secretion.

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.

Effects of starvation on valine and alanine transport across the intestinal mucosal border in sea bass, Dicentrarchus labrax

Kinetics of intestinal transport of L-alanine and L-valine (substrates of the A-system and the L-system, respectively, in mammals) across the brush-border membrane in sea bass, Dicentrarchus labrax, were studied on intact mucosa using a short-term uptake technique. When fish were starved for 4-8 weeks, total influx (mucosa-to-cell) of valine fell owing to disappearance or modification of the diffusion component. The maximum influx rate of saturable component increased but its affinity (reflected by the Michaelis constant) decreased. Alanine transport by Na(+)-dependent and diffusion pathways was unchanged after starvation. Fasting also induced an almost 20% decrease in the length of intestinal microvilli.