Sepsis-Induced Inhibition of Contractile Function of Lymphatic Nodes.

Inflammation accompanies most pathological processes, while the lymphatic system takes part in both the development and resolution of inflammation. We studied the contractile function of rat lymph nodes after cecal ligation and puncture (CLP). In 24 h after CLP, the mesenteric lymph nodes were removed and placed in the myograph chamber. After CLP, the lymph nodes showed lower tension than lymph nodes from sham-operated animals (control). The expression of inducible NO synthase, cyclooxygenase-2, and cystathionine-γ-lyase was observed in the lymph nodes of CLP rats. NO, prostaglandins, and H2S formed during inflammation inhibited contractile activity of smooth muscle cells in the capsule of the lymph nodes, which manifested itself in inhibition of phase contractions and a decrease in the tone of their capsule.

The Role of Hydrogen Sulfide in the Dilatation of Mesenteric Lymphatic Vessels in Bulls.

We studied the effects and mechanisms of action of NaHS, an H2S donor, on bovine isolated mesenteric efferent lymphatic vessels pre-contracted with phenylephrine. NaHS induced concentration-dependent relaxation of lymphatic vessels. Removal of the endothelium reduced, but did not completely abolish the relaxing effect of NaHS. Application of NO synthase inhibitor L-NAME, soluble guanylyl cyclase inhibitor ODQ, blocker ATP-sensitive K+ channels glibenclamide, and a combination of blockers of Ca-activated K+ channels of small and intermediate conductance charybdotoxin and apamin attenuated relaxation of lymphatic vessels. Thus, H2S produces a pleiotropic effect on lymphatic vessels; vasorelaxant effect is achieved by several parallel mechanisms. H2S induces relaxation of lymphatic vessels and modulates the rate of lymph transport, thereby affecting the development of immune processes in the body.

Relaxing Effect of Hydrogen Sulfide on Isolated Bovine Mesenteric Lymph Nodes.

We studied the effects and mechanisms of action of NaHS, an H2S donor, on isolated phenylephrine-precontracted bovine mesenteric lymph nodes. NaHS induced concentration-dependent relaxation of lymph nodes. Removal of the endothelium reduced, but did not abolish the relaxing effect of NaHS. The relaxing effect was reduced by NO synthase inhibitor L-NAME, soluble guanylate cyclase inhibitor ODQ, ATP-sensitive K+ channel blocker glibenclamide, and a combination charybdotoxin+apamin (blockers of small- and intermediate-conductance Ca2+-activated K+ channels). Thus, the relaxing effect of H2S on lymph nodes is mediated by several parallel mechanisms. H2S induces relaxation of LN and modulates the rate of lymph transport, thereby affecting the development of immune processes in the body.

Contribution of Hydrogen Sulfide to Dilation of Rat Cerebral Arteries after Ischemia/Reperfusion Injury.

The study examined the effect of H2S on the tone of cerebral arteries in rats after global cerebral ischemia/reperfusion injury and cooperation between NO and H2S in the control over cerebral circulation during the postischemic period. In control sham-operated and in experimental rats with ischemia/reperfusion injury, the diameter of pial arteries was repeatedly measured in vivo under a light microscope after removal of parietal bone and dura mater in 1 h and in 7 days after the surgery. The study established that H2S is an important signaling molecule in pial arteries, where it is responsible for vasodilation. Interaction of H2S and NO augmented dilation of pial arteries; in these arteries, H2S up-regulated the effect of NO/cGMP/sGC/PKG signaling pathways. Partially, the dilating effect of H2S is realized via activation of ATP-sensitive K+ channels in plasmalemma of smooth muscle cells. In the brain, ischemia/reperfusion injury degrades the ability of pial arteries to dilate via inhibition of NO-mediated signaling pathway.

Mechanisms of Blood Flow Regulation in the Skin during Stimulation of the Spinal Cord in Humans.

Changes in the blood flow in the shin skin were observed by laser Doppler flowmetry after transcutaneous electrical spinal cord stimulation (TSCS) by subthreshold bipolar pulses with a frequency of 30 Hz in 12 healthy subjects. It was found that TSCS in the area of the T11 and L1 vertebrae led to a significant increase in skin blood flow. The microcirculation rate increased by more than 85% relative to the baseline at a stimulus intensity of 90% of the motor threshold. Cutaneous blood flow activization by TSCS is implemented mainly through the antidromic stimulation of sensory nerve fibers. Nitric oxide (NO) is an important mediator that contributes to vasodilation and increase in cutaneous blood flow upon TSCS. NO is predominantly of endothelial origin.

Endothelium-dependent Hyperpolarization-Mediated Relaxation Pathway in Bovine Mesenteric Lymph Nodes.

Endothelium-dependent relaxation mechanisms have been studied in phenylephrine-precontracted capsules of bovine mesenteric lymph nodes studied in vitro. Tetraethylammonium chloride and TRAM-34 in a solution with L-NAME and Indomethacin, which suppress the production NO and prostacyclin of endothelium, increased the tone of the lymph nodes. We believe that in bovine mesenteric lymph nodes, the dilation mechanism is mediated by hyperpolarization of the endothelium, which is associated with activation of large- and intermedium conductance Ca2+-activated potassium channels.

Cerebral Blood Flow in SHR Rats after Transplantation of Mesenchymal Stem Cells.

Intracerebral transplantation of mesenchymal stem cells to 6- and 12-month-old SHR rats induced angiogenesis in the pia mater. In 6-months-old SHR rats, perfusion in the brain tissue after cell transplantation considerably increased, while in 12-month-old rats it remained practically unchanged. We also observed marked activation of regulatory processes in the cerebral vascular system, most pronounced in 12-month-old rats. Neurogenic and myogenic tone of cerebral vessels increased significantly, while endothelium-dependent tone slightly decreased. The increase in neurogenic and myogenic tone of blood vessels in SHR rats at the age of 6 and 12 months after transplantation of stem cells can be explained by the formation of new smooth muscle cells in the pre-existing arteries walls. Greater muscle mass developed stronger force and contributed to narrowing of the arterial lumen, as a result, there was no increase in blood flow despite the downstream angiogenesis. A slight decrease in endothelium-dependent tone can be explained by increased production of vasodilators by newly formed endothelial cells.

Protective Effect of Dexamethasone on Lipopolysaccharide-Induced Inhibition of Contractile Function of Isolated Lymphatic Vessels and Nodes.

LPS has an inhibitory effect on contractile activity of bovine mesenteric lymphatic vessels and nodes and causes a pronounced decrease in the tone and phase contractions. The selective inhibitor of inducible NO synthase, 1400W, and cyclooxygenase-2 selective inhibitor, dynastat, significantly attenuated the inhibitory effect of LPS. Dexamethasone interferes with the inhibitory effect of LPS on bovine lymphatic vessels and nodes. It was concluded that LPS stimulates expression of inducible NO synthase and cyclooxygenase-2 in endothelial and smooth muscle cells of lymphatic vessels and nodes. Dexamethasone has a pronounced protective effect on the contractile function of lymphatic vessels and nodes affected by LPS and suppresses the expression of inducible NO synthase and cyclooxygenase-2.

Inhibitory Effect of Interferons on Contractive Activity of Bovine Mesenteric Lymphatic Vessels and Nodes.

We studied the effect of IFNα-2b and IFNß-1a on phasic and tonic contractions of isolated bovine mesenteric lymphatic vessels and nodes. IFNα-2b and IFNß-1a in concentrations of 250-1000 U/ml produced dose-dependent negative chronotropic and inotropic effects on spontaneous phasic contractions and tonus of lymphatic vessels and nodes. In de-endothelialized lymphatic vessels and nodes, IFNα-2b and IFNß-1a in the same concentrations had less pronounced inhibitory effect on spontaneous contraction and tonus. L-NAME (100 µM) and charybdotoxin (0.1 µM with 0.5 µM apamine) significantly attenuated the inhibitory effect of IFNα-2b on phasic and tonic contractions of lymph nodes. L-NAME (100 µM) and indomethacin (10 µM) significantly reduced the IFNα-2b-induced inhibitory effect on phasic and tonic contractions of lymph node. These results indicate that IFNα-2b and IFNß-1a have a pronounced inhibitory effect on the phasic and tonic contractions of bovine mesenteric lymphatic vessels and nodes. The responses are endothelium-dependent and are determined by production of NO and endothelium-dependent hyperpolarizing factor by endotheliocytes in lymphatic vessels and by production of NO and prostacyclin by endotheliocytes in the lymphatic nodes.

Atrial Natriuretic Peptide Inhibits Spontaneous Contractile Activity of Lymph Nodes.

Atrial natriuretic peptide dose-dependently inhibited spontaneous phase and tonic activity of smooth muscle strips from the capsule of isolated bovine mesenteric lymph nodes. Pretreatment with L-NAME, diclofenac, and methylene blue had practically no effect on the peptide-induced relaxation responses. In contrast, glibenclamide significantly reduced the inhibitory effect of atrial natriuretic peptide. We suppose that the NO-dependent and cyclooxygenase signaling pathways are not involved in implementation of the inhibitory effects of atrial natriuretic peptide. ATP-sensitive K(+)-channels of the smooth muscle cell membrane are the last component in the signaling pathway leading to relaxation of smooth muscles of the lymph node capsule caused by atrial natriuretic peptide; activation of these channels leads to membrane hyperpolarization and smooth muscle relaxation.

Effect of Heparin on Contractile Activity of Lymph Node Capsule.

Experiments on smooth muscle strips isolated from the capsule of bovine mesenteric lymph node showed that heparin low concentrations (0.010-0.025 U/ml) stimulating spontaneous isometric phasic contractions of smooth muscles, but higher heparin concentrations reduced or even completely eliminated these contractions. The inhibitory effects of heparin were presumably realized via stimulation of NO production by endothelial cells of the subcapsular space followed by activation of ATP-sensitive potassium channels of capsular myocytes and via modulation of prostaglandin synthesis.

[Transport function of the lymph nodes in young and old animals].

The paper discusses the age-related changes of contractile activity of the capsule of the lymph nodes, underlying their transport function. The results of the studies conducted on the mesenteric lymph nodes of young and old bulls are presented. The changes in the contractile function of the capsule of the lymph nodes were revealed in the older animals. The changes appeared in the decrease of the amplitude and increase of the phase contraction frequency which are based on the replacement of smooth muscle by connective tissue, the enhancement of pacemaker activity of smooth muscle cells and endothelial dysfunction of lymph node cells.

Involvement of α-adrenoceptors to the implementation of the contractile effects in the capsule of mesenteric lymph nodes in response to electrostimulation.

We studied changes in the contractile function of smooth muscle cells in bovine mesenteric lymph node capsule caused by electrical stimulation of nerve fibers in vitro. It was found that electrostimulation increased tonic tension and frequency of smooth muscle contractions in the node capsule. Tetrodotoxin prevented the stimulatory effect of electrical stimulation on the smooth muscle cells. Phentolamine, prazosin, and yohimbine significantly reduced the capsule response to electrical stimulation and norepinephrine application. It was concluded that excitation of nerve fibers in the capsule of bovine mesenteric lymph nodes upon electrical stimulation is realized, at least in part, via activation of α1-adrenoceptors and, to a lesser extent, via α2-adrenoceptors located on the membrane of smooth muscle cells.

Effect of histamine on contractile activity of smooth muscles in bovine mesenteric lymph nodes.

The effects of histamine and mechanisms of its action on the capsular smooth muscle cells of mesenteric lymph nodes were examined on isolated capsular strips under isometric conditions. Histamine (1×10(-8)-5×10(-7) M) decreased the tone of capsular smooth muscle cells and the frequency of phasic contractions. At high concentrations (more than 5×10(-6) M), histamine increased the amplitude and frequency of phasic contractions against the background of increased tonic stress. The effects of histamine were dose-dependent and were realized via direct stimulation of H(1)- and H(2)-receptors on the membrane of smooth muscle cells.

[Lymph transport in lymphatic nodes: mechanisms of regulation].

The role of lymphatic vessels in maintaining the homeostasis of tissue, lymph transport regulation and mechanisms of lymph flow is well known. Investigations of lymph node are mainly focused on processes of immune reactions and metastasis. Their role in the transport of lymph has not been almost researched; few studies have investigated the mechanisms of regulation of lymph flow in the lymph nodes. The active transport function of lymph nodes is provided by the smooth muscle contractions of the capsule of the lymph nodes. The changes of these contractions during electrical stimulation of nerve endings and effect of some biologically active substances are described in this article. The mechanisms of regulation of smooth muscle contractility and lymph nodes capsule transport functions: myogenic self-regulation, endothelium-depended and nerve regulation, regulation of histamine and heparin.

[Effects of histamine on contractile activity of lymphatic node capsules. The NO role].

Effects of histamine (10(-9)--5 x 10(-5) M) on the phase and tonic contractile activity of capsular smooth muscles of isolated bovine mesentery lymph node were investigated. Dual dose-depended effect of histamine was found. Low concentrations of histamine less than 10(-7) M caused a decrease of contractile activity, whereas higher concentrations of histamine (more than 5 x 10(-7) M) resulted in increase of the phase and tonic contractions. Both H1- and H2-receptors of smooth muscle cells are involved in the response. Much of the relaxing histamine-induced response is produced by the stimulation of the endothelial cells. We believe that activating effect of histamine is due to the excitation of H1-receptors located on the membrane of myocytes, whereas its inhibitory effect occurs in two ways: 1) via excitation of H2-receptors located on the membrane of myocytes; 2) via stimulation of the NO production by the endothelial cells of lymph node sinus.

[Effects of stimulation of nervous fibres upon contractile activity of the tracheobronchial lymphatic node capsules' smooth muscles].

The contractile activity of smooth muscle of tracheobronchial lymph nodes' capsules was recorded in vitro. The field electric stimulation (0.5 ms pulses, 55 V nominal, 4 min trains at frequencies 0.5, 1, 2, 4, 8, 16 and 32 Hz) of strips from lymph node produced a frequency-dependent increase in baseline tension and frequency of phase contractions. Evoked contractions were significantly (about 80%) reduced by tetrodotoxin (1 x 10(-6) M). The blockage of M-cholinoreceptors with atropine (1 x 10(-6) M) did not affect the field-evoked responses. Contractile field-evoked effects were significantly reduced by the phentolamine (1 x 10(-7)-1 x 10(-6) M) but not completely. Field-evoked contractions were slightly affected by the propranolol (1 x 10(-7)-1 x 10(-6) M). We conclude that the contractile activity of bovine tracheobronchial lymph node capsular smooth muscle is modulated by excitatory adrenergic nerves.

Mechanical properties of lymph node capsule.

We studied the relationship between the length and tension in isolated strips of the capsules of bovine mesenteric lymph nodes. The deformation-strain and radius-pressure relationships were established in the lymph node. The capsule possesses high distensibility, modulus of elasticity at optimal tension was 0.09×10(5) N/m2. Smooth muscle activation produces a 6-fold increase of modulus of elasticity. Maximum active stress in the capsule was recorded at a length of 1.1 L0 and maximal active pressure (4.5 cm H2O) at 0.9 L0.

Effect of anoceptin on detoxifying function of the liver.

The absence of negative effects of anoceptin on the liver tissue and detoxifying function was proven experimentally in vitro and in vivo. It was proven for the first time that comenic acid (anoceptin active substance) in concentrations of 10(-4)-10(-12) does not modulate the growth of liver explants from 10-12-day chicken embryos. The effect of anoceptin on the detoxifying function of the liver was studied on Wistar rats under conditions of hexenal-induced sleep. The drug was injected into the caudal vein for 90 days in a daily dose of 5, 100, or 300 mg/kg. The duration of hexenal-induced sleep was evaluated before and on days 30 and 90 of the study. Anoceptin did not modify the duration of hexenal-induced sleep and the status and detoxifying function of the liver.

Heparin inhibits contraction of smooth muscle cells in lymphatic vessels.

Heparin in concentrations of 10-50 U/ml produced a decrease in the amplitude and frequency of phasic contractions of smooth muscle cells of bovine mesenteric lymphatic vessels. Vascular wall tension was reduced under these conditions. The endothelium-dependent effect of heparin is realized via an increase in the production of nitric oxide by endothelial cells and, to a lesser degree, via the stimulation of prostacyclin synthesis.