| 1. |
- Ahl, David, et al.
(author)
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Turning Up the Heat : Local Temperature Control During in vivo Imaging of Immune Cells
- 2019
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In: Frontiers in Immunology. - : FRONTIERS MEDIA SA. - 1664-3224. ; 10
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Journal article (peer-reviewed)abstract
- Intravital imaging is an invaluable tool for studying the expanding range of immune cell functions. Only in vivo can the complex and dynamic behavior of leukocytes and their interactions with their natural microenvironment be observed and quantified. While the capabilities of high-speed, high-resolution confocal and multiphoton microscopes are well-documented and steadily improving, other crucial hardware required for intravital imaging is often developed in-house and less commonly published in detail. In this report, we describe a low-cost, multipurpose, and tissue-stabilizing in vivo imaging platform that enables sensing and regulation of local tissue temperature. The effect of tissue temperature on local blood flow and leukocyte migration is demonstrated in muscle and skin. Two different models of vacuum windows are described in this report, however, the design of the vacuum window can easily be adapted to fit different organs and tissues.
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| 2. |
- Liu, Haoyu, et al.
(author)
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Distinct B cell subsets in Peyer's patches convey probiotic effects by Limosilactobacillus reuteri
- 2021
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In: Microbiome. - : Springer Nature. - 2049-2618. ; 9
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Journal article (peer-reviewed)abstract
- Background: Intestinal Peyer's patches (PPs) form unique niches for bacteria-immune cell interactions that direct host immunity and shape the microbiome. Here we investigate how peroral administration of probiotic bacterium Limosilactobacillus reuteri R2LC affects B lymphocytes and IgA induction in the PPs, as well as the downstream consequences on intestinal microbiota and susceptibility to inflammation.Results: The B cells of PPs were separated by size to circumvent activation-dependent cell identification biases due to dynamic expression of markers, which resulted in two phenotypically, transcriptionally, and spatially distinct subsets: small IgD(+)/GL7(-)/S1PR1(+)/Bcl6, CCR6-expressing pre-germinal center (GC)-like B cells with innate-like functions located subepithelially, and large GL7(+)/S1PR1(-)/Ki67(+)/Bcl6, CD69-expressing B cells with strong metabolic activity found in the GC. Peroral L. reuteri administration expanded both B cell subsets and enhanced the innate-like properties of pre-GC-like B cells while retaining them in the sub-epithelial compartment by increased sphingosine-1-phosphate/S1PR1 signaling. Furthermore, L. reuteri promoted GC-like B cell differentiation, which involved expansion of the GC area and autocrine TGF beta-1 activation. Consequently, PD-1-T follicular helper cell-dependent IgA induction and production was increased by L. reuteri, which shifted the intestinal microbiome and protected against dextran-sulfate-sodium induced colitis and dysbiosis.Conclusions: The Peyer's patches sense, enhance and transmit probiotic signals by increasing the numbers and effector functions of distinct B cell subsets, resulting in increased IgA production, altered intestinal microbiota, and protection against inflammation.
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| 3. |
- Nylander, Olof, et al.
(author)
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Effects of α2-adrenoceptor stimulation on luminal alkalinisation and net fluid flux in rat duodenum
- 2022
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 17:8
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Journal article (peer-reviewed)abstract
- The sympathetic nervous system is highly involved in the regulation of gastrointestinal functions such as luminal alkalinisation and fluid absorption. However, the exact mechanisms are not clear. This study aimed to delineate how α2-adrenergic receptor stimulation reduces duodenal luminal alkalinisation and induces net fluid absorption. This was tested by perfusing the duodenum of anesthetized rats with isotonic solutions devoid of Cl- and/or Na+, in the absence and presence of the α2-adrenoceptor agonist clonidine. The clonidine was also studied in rats treated with dimethylamiloride (a Na+/H+ exchange inhibitor), vasoactive intestinal peptide, and the nicotinic receptor antagonist hexamethonium. Clonidine reduced luminal alkalinisation and induced net fluid absorption. The Cl--free solution decreased luminal alkalinisation and abolished net fluid absorption, but did not prevent clonidine from doing so. Both the Na+-free solution and luminal dimethylamiloride increased luminal alkalinisation and abolished net fluid absorption, effects counteracted by clonidine. The NaCl-free solution (D-mannitol) did not affect luminal alkalinisation, but reduced net fluid absorption. Clonidine reduced luminal alkalinisation and induced net fluid absorption in rats perfused luminally with mannitol. However, clonidine did not affect the vasoactive intestinal peptide-induced increase in luminal alkalinisation or fluid secretion. Pre-treatment with hexamethonium abolished the effects of clonidine on luminal alkalinisation and net fluid flux. In summary, our in vivo experiments showed that clonidine-induced reduction in luminal alkalinisation and induction of net fluid absorption was unrelated to luminal Na+ and Cl-, or to apical Na+/H+ or Cl-/HCO3- exchangers. Instead, clonidine seems to exert its effects via suppression of nicotinic receptor-activated acetylcholine secretomotor neurons.
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| 4. |
- Sedin, John, 1982-, et al.
(author)
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High Resolution Intravital Imaging of the Renal Immune Response to Injury and Infection in Mice
- 2019
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In: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 10
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Journal article (peer-reviewed)abstract
- We developed an experimental set up that enables longitudinal studies of immune cell behavior in situ in the challenged as well as unchallenged kidney of anesthetized mice over several hours. Using highly controlled vacuum to stabilize the kidney, the superficial renal cortex could continuously be visualized with minimal disruption of the local microenvironment. No visible changes in blood flow or neutrophils and macrophages numbers were observed after several hours of visualizing the unchallenged kidney, indicating a stable tissue preparation without apparent tissue damage. Applying this set up to monocyte/macrophage (CX(3)CR1(GFP/+)) reporter mice, we observed the extensive network of stellate-shaped CX(3)CR1 positive cells (previously identified as renal mononuclear phagocytes). The extended dendrites of the CX(3)CR1 positive cells were found to bridge multiple capillaries and tubules and were constantly moving. Light induced sterile tissue injury resulted in rapid neutrophil accumulation to the site of injury. Similarly, microinfusion of uropathogenic Escherichia coli into a single nephron induced a rapid and massive recruitment of neutrophils to the site of infection, in addition to active bacterial clearance by neutrophils. In contrast, the kidney resident mononuclear phagocytes were observed to not increase in numbers or migrate toward the site of injury or infection. In conclusion, this model allows for longitudinal imaging of responses to localized kidney challenges in the mouse.
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| 5. |
- Sedin, John, 1982-, et al.
(author)
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Prevention of duodenal ileus reveals functional differences in the duodenal response to luminal hypertonicity in Sprague-Dawley and Dark Agouti rats
- 2014
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In: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 210:3, s. 573-589
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Journal article (peer-reviewed)abstract
- Aim: The mechanism by which the duodenum adjusts the luminal osmolality remains unclear. The aim was to compare the duodenal osmoregulation in response to different hyperosmolar solutions in Sprague-Dawley and Dark Agouti rats and to elucidate whether cyclooxygenase-2 inhibition affects these responses.Methods: The duodenum was perfused in situ with a 700-milliosmolar solution (NaCl alone, D-glucoseNaCl, D-mannitolNaCl or orange juice), and the effects on the duodenal motility, mucosal permeability, luminal alkalinization, fluid flux and osmoregulation were assessed in anaesthetized rats.Results: The change in net fluid flux and luminal osmolality, in response to a given hyperosmolar solution, was almost identical in control rats of both strains. In control rats, hypertonic D-glucose-NaCl induced fluid secretion only in the presence of phlorizin, an inhibitor of SGLT1. Cyclooxygenase-2 inhibition potentiated the hypertonicity-induced fluid secretion and increased the osmolality-adjusting capability in both strains, but the responses were greater in Dark Agouti rats. While cyclooxygenase-2-inhibited Dark Agouti rats responded to the hyperosmolar solutions with depression of motility and increased mucosal permeability, these effects were absent or smaller in the Sprague-Dawley strain. In contrast, orange juice induced the same duodenal responses in cyclooxygenase-2-inhibited Dark Agouti and Sprague-Dawley rats.Conclusion: The duodenum possesses the ability to absorb fluid despite a very high luminal osmolality. Inhibition of cyclooxygenase-2 markedly enhanced the capability of the duodenum to secrete fluid and to decrease luminal osmolality, irrespective of the hyperosmolar solution or the rat strain used, and revealed notable differences between the two strains with regard to their osmolality-adjusting capability.
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| 6. |
- Sedin, John, 1982-
(author)
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Prevention of Postoperative Duodenal Ileus by COX-2 Inhibition Improves Duodenal Function in Anaesthetised Rats
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Abdominal surgery inhibits gastrointestinal motility, a phenomenon referred to as postoperative ileus. Since the postoperative ileus disturbs duodenal physiology it is important to minimize the side effects of this condition. Recent experiments in our laboratory show that treatment of anaesthetised rats with parecoxib, a selective cyclooxygenase-2 inhibitor, prevents duodenal postoperative ileus, increases duodenal mucosal bicarbonate secretion and improves other functions as well. One aim of the thesis was to investigate whether removal of luminal chloride affect the parecoxib- and the vasoactive intestinal peptide (VIP)-induced stimulation of duodenal mucosal bicarbonate secretion. The proximal duodenum of anaesthetised Dark Agouti rats was perfused with isotonic solutions containing zero or low Cl- and the effect on luminal alkalinisation determined. The basal as well as the parecoxib-induced increase in alkalinisation, but not that stimulated by VIP, were markedly reduced in the absence of luminal Cl-.One important function of the duodenum is to adjust luminal osmolality towards that in the blood. It is believed that the adjustment of osmolality in the duodenum is achieved by osmosis and diffusion of electrolytes along their concentration gradients and that these processes occur predominately paracellularly. Another aim of the thesis was to examine whether prevention of postoperative ileus affects the duodenal response to luminal hypertonicity. The proximal duodenum of anaesthetised Dark Agouti and Sprague-Dawley rats were perfused with hypertonic solutions of different composition and osmolality and the effects on duodenal motility, alkaline secretion, transepithelial fluid flux, mucosal permeability and the adjustment of luminal osmolality were determined in absence and presence of parecoxib.It is concluded that COX-2 inhibition increases duodenal mucosal bicarbonate secretion by stimulating apical Cl-/HCO3- exchange in duodenocytes. Furthermore, pretreatment of anaesthetised rats with parecoxib improves a number of duodenal functions in both rat strains that contribute to improve the ability to adjust luminal osmolality. The choice of rat strain is another important feature to consider when interpreting the results because the DA strain was more responsive to luminal hypertonicity than the SD strain. Finally, several evidences are provided to suggest that the adjustment of luminal osmolality in the rat duodenum is a regulated process.
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| 7. |
- Sedin, John, 1982-, et al.
(author)
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The Impact of alpha-Adrenoceptors in the Regulation of the Hypotonicity-Induced Increase in Duodenal Mucosal Permeability In Vivo
- 2021
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In: Pharmaceutics. - : MDPI. - 1999-4923. ; 13:12
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Journal article (peer-reviewed)abstract
- The duodenal mucosa is regularly exposed to a low osmolality, and recent experiments suggest that hypotonicity increases mucosal permeability in an osmolality-dependent manner. The aim was to examine whether the sympathetic nervous system, via action on alpha-adrenoceptors, affects the hypotonicity-induced increase in duodenal mucosal permeability. The duodenum of anaesthetised rats was perfused in vivo with a 50 mM NaCl solution in the presence of adrenergic alpha-adrenoceptor drugs. Studied were the effects on mucosal permeability (blood-to-lumen clearance of Cr-51-EDTA), arterial blood pressure, luminal alkalinisation, transepithelial fluid flux, and motility. Hypotonicity induced a six-fold increase in mucosal permeability, a response that was reversible and repeatable. The alpha(2)-adrenoceptor agonist clonidine abolished the hypotonicity-induced increase in mucosal permeability, reduced arterial blood pressure, inhibited duodenal motility, and decreased luminal alkalinisation. The alpha(2)-adrenoceptor antagonists, yohimbine and idazoxan, prevented the inhibitory effect of clonidine on the hypotonicity-induced increase in mucosal permeability. The alpha(1)-agonist phenylephrine or the alpha(1)-antagonist prazosin elicited their predicted effect on blood pressure but did not affect the hypotonicity-induced increase in mucosal permeability. None of the alpha(1)- or alpha(2)-adrenoceptor drugs changed the hypotonicity-induced net fluid absorption. In conclusion, stimulation of the adrenergic alpha(2)-adrenoceptor prevents the hypotonicity-induced increase in mucosal permeability, suggesting that the sympathetic nervous system has the capability to regulate duodenal mucosal permeability.
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