Hypertonic saline enhances host defense to bacterial challenge by augmenting Toll-like receptors*

Hypertonic Saline Induces Host Protective Immune Responses against Brucella abortus Infection in Mice

Hypertonic saline (HTS) resuscitation can enhance immune responses against various pathogens, however, the effect of HTS on brucellosis is yet to be defined. In this study, we found that HTS inhibited Brucella infection in mice by augmenting Th1 immunity. HTS treatment enhanced the serum cytokines production and the expression of nitric oxide synthase (NOS2) and nuclear factor kappa B (NF-ĸB) p50 and p65, crucial anti-Brucella effectors in splenocytes. In addition, HTS treatment also inhibited the phosphorylation of MAPK signaling, accompanied by the down-regulation of the autophagy marker LC3B-II. Due to directing an appropriate immune response, HTS treatment substantially decreased bacterial burden in spleen and liver tissues. In summary, corroborating previous studies showing the antimicrobial effects of HTS, our findings indicate that HTS treatment triggers a protective immune response against Brucella infection. Additionally, these results provide promising evidence of the immunomodulatory role of HTS in controlling bacterial infections.

High Na+ Environments Impair Phagocyte Oxidase-Dependent Antibacterial Activity of Neutrophils

Infection and inflammation can augment local Na⁺ abundance. These increases in local Na⁺ levels boost proinflammatory and antimicrobial macrophage activity and can favor polarization of T cells towards a proinflammatory Th17 phenotype. Although neutrophils play an important role in fighting intruding invaders, the impact of increased Na⁺ on the antimicrobial activity of neutrophils remains elusive. Here we show that, in neutrophils, increases in Na⁺ (high salt, HS) impair the ability of human and murine neutrophils to eliminate Escherichia coli and Staphylococcus aureus. High salt caused reduced spontaneous movement, degranulation and impaired production of reactive oxygen species (ROS) while leaving neutrophil viability unchanged. High salt enhanced the activity of the p38 mitogen-activated protein kinase (p38/MAPK) and increased the interleukin (IL)-8 release in a p38/MAPK-dependent manner. Whereas inhibition of p38/MAPK did not result in improved neutrophil defense, pharmacological blockade of the phagocyte oxidase (PHOX) or its genetic ablation mimicked the impaired antimicrobial activity detected under high salt conditions. Stimulation of neutrophils with phorbol-12-myristate-13-acetate (PMA) overcame high salt-induced impairment in ROS production and restored antimicrobial activity of neutrophils. Hence, we conclude that high salt-impaired PHOX activity results in diminished antimicrobial activity. Our findings suggest that increases in local Na⁺ represent an ionic checkpoint that prevents excessive ROS production of neutrophils, which decreases their antimicrobial potential and could potentially curtail ROS-mediated tissue damage.

Sodium Chloride Aggravates Arthritis via Th17 Polarization

PURPOSE

Sodium chloride (NaCl) has been proposed as a driving factor in autoimmune diseases through the induction of pathogenic CD4⁺ T helper cells that produce interleukin-17 (Th17 cells). This study investigated the effects of NaCl on inflammatory arthritis in mice and humans.

MATERIALS AND METHODS

Collagen-induced arthritis (CIA) mice were fed a normal or high-salt diet ad libitum, and clinical and histologic features of arthritis were evaluated. The proportion of Th17 cells in the spleens of CIA mice fed a normal or high-salt diet was evaluated by flow cytometry, and the expression of IL-17 in joints and intestines was determined by immunohistochemical staining. We also analyzed the effect of NaCl on Th17 differentiation from peripheral blood monocytes of patients with rheumatoid arthritis (RA) and osteoarthritis (OA) and evaluated the contents of sodium and IL-17 in the synovial fluid of RA and OA patients.

RESULTS

NaCl increased murine and human Th17 cell differentiation in a dose-dependent manner. Clinical and histological arthritis was more severe in the high-salt-fed CIA mice, compared to control CIA mice. The proportion of Th17 cells among splenocytes was higher in CIA mice fed a high-salt diet. Expression of synovial and intestinal IL-17 was also higher in high-salt-fed CIA mice. Comparison of synovial fluid between RA patients and OA patients revealed that Na⁺ and IL-17 were more abundant in RA synovial fluid.

CONCLUSION

This study suggests that NaCl can aggravate arthritis by affecting Th17 differentiation. Accordingly, limiting salt intake may be helpful for treating inflammatory arthritis, such as RA.

Microglia-derived extracellular vesicles in Alzheimer's Disease: A double-edged sword

Extracellular vesicles (EVs), based on their origin or size, can be classified as apoptotic bodies, microvesicles (MVs)/microparticles (MPs), and exosomes. EVs are one of the new emerging modes of communication between cells that are providing new insights into the pathophysiology of several diseases. EVs released from activated or apoptotic cells contain specific proteins (signaling molecules, receptors, integrins, cytokines), bioactive lipids, nucleic acids (mRNA, miRNA, small non coding RNAs, DNA) from their progenitor cells. In the brain, EVs contribute to intercellular communication through their basal release and uptake by surrounding cells, or release into the cerebrospinal fluid (CSF) and blood. In the central nervous system (CNS), EVs have been suggested as potential carriers in the intercellular delivery of misfolded proteins associated to neurodegenerative disorders, such as tau and amyloid β in Alzheimer's Disease (AD), α-synuclein in Parkinson's Disease (PD), superoxide dismutase (SOD)1 in amyotrophic lateral sclerosis and huntingtin in Huntington's Disease. Multiple studies indicate that EVs are involved in the pathogenesis of AD, although their role has not been completely elucidated. The focus of this review is to analyze the new emerging role of EVs in AD progression, paying particular attention to microglia EVs. Recent data show that microglia are the first myeloid cells to be activated during neuroinflammation. Microglial EVs in fact, could have both a beneficial and a detrimental action in AD. The study of EVs may provide specific, precise information regarding the AD transition stage that may offer possibilities to intervene in order to retain cognition. In chronic neurodegenerative diseases EVs could be a novel biomarker to monitor the progression of the pathology and also represent a new therapeutical approach to CNS diseases.

Increased serum NKG2D-ligands and downregulation of NKG2D in peripheral blood NK cells of patients with major burns

Immune suppression following major thermal injury directly impacts the recovery potential. Limited data from past reports indicate that natural killer cells might be suppressed due to a putative soluble factor that has remained elusive up to date. Here we comparatively study cohorts of patients with Major and Non-Major Burns as well as healthy donors. MICB and ULBP1 are stress ligands of NKG2D that can be induced by heat stress. Remarkably, serum concentration levels of MICB and ULBP1 are increased by 3-fold and 20-fold, respectively, already within 24h post major thermal injury, and are maintained high for 28 days. In contrast, milder thermal injuries do not similarly enhance the serum levels of MICB and ULBP1. This kinetics coincides with a significant downregulation of NKG2D expression among peripheral blood NK cells. Downregulation of NKG2D by high concentration of soluble MICB occurs in cancer patients and during normal pregnancy due to over production by cancer cells or extravillous trophoblasts, respectively, as an active immune-evasion mechanism. In burn patients this seems an incidental outcome of extensive thermal injury, leading to reduced NKG2D expression. Enhanced susceptibility of these patients to opportunistic viral infections, particularly herpes viruses, could be explained by the reduced NKG2D expression. Further studies are warranted for translation into innovative diagnostic or therapeutic technologies.

Salt and miscarriage: Is there a link?

Salt is a major mineral element that plays fundamental roles in health and disease. Excessive salt intake is a major cause of hypertension, cardiovascular disease and stroke. Miscarriage and preeclampsia are the most common pregnancy complications with multiple etiological factors, including inflammatory and autoimmune conditions. More recently, different studies indicated that excessive salt intake is involved in the development of inflammatory processes through induction of T helper-17 pathway and their inflammatory cytokines. On the other hand, several studies indicated the pivotal role of inflammation in the etiology of miscarriage, preeclampsia and adverse pregnancy outcome. Here, it is hypothesized that excessive salt intake around the time of conception or during pregnancy can trigger inflammatory processes, which consequently associated with increased risk of miscarriage, preeclampsia or adverse pregnancy outcome. Thus, this hypothesis suggests that low salt intake around the time of conception or during pregnancy can decrease the risk of miscarriage or adverse pregnancy outcome. This hypothesis also offers new insights about the role of salt in the etiology of miscarriage and preeclampsia.

Biological role of Toll-like receptor-4 in the brain

The Toll-like receptors (TLRs) are a family of microbe-sensing receptors that play a central role in the regulation of the host immune system. TLR4 has been described in the brain and seems to regulate some physiological processes, such as neurogenesis. TLR4 has also been reported to play a role during neurodegenerative disorders, including Alzheimer's disease, amyotrophic lateral sclerosis, multiple sclerosis and Parkinson's disease. This review is focused on reports concerning recent insights into the role and activation mechanisms of TLR4 in the brain, in pathological and physiological conditions, as well as the therapeutic benefit that could derive from TLR4 modulation.

[Septic shock. Update of treatment using hypertonic saline and antidiuretic hormone-vasopressin]

Safety in the use of small volumes of hypertonic saline solution for hypovolaemic shock and in the treatment of intracranial hypertension has been demonstrated in studies in the field of resuscitation. There is little experience of this for septic shock in humans. Beneficial immunomodulatory effects have been detected in pre-clinical studies. Interactions with the pituitary-adrenal axis and with the secretion of anti-diuretic hormone are varied and suggestive, but are not sufficiently understood. On the other hand, vasopressin has cardiovascular, osmoregulatory, and coagulation effects, and also acts on the hypothalamic-pituitary-adrenal axis. There is a relative deficit of vasopressin in septic shock. Its use in these patients does not seem to have any advantages as regards mortality, but may be beneficial in patients at risk from acute renal failure, or those who receive corticosteroids. Terlipressin is a vasopressin analogue that has also been studied. The synergy between vasopressin and hypertonic saline is a hypothesis that is mainly supported in pre-clinical studies. The use of hypertonic saline solution in septic shock, although promising, is still experimental, and must be restricted to the field of controlled clinical trials.

Estrogen augments the protection of hypertonic saline treatment from mesenteric ischemia-reperfusion injury

Either estrogen or hypertonic saline (HTS) administration can decrease lung inflammation after ischemia-reperfusion. The present study investigated whether combined treatment with estrogen and HTS could provide further protection from mesenteric ischemia-reperfusion (MSIR) injury. Male C3H/HeOuJ mice were randomly segregated into the following groups: sham-operated (sham), vehicle treatment followed by MSIR (vehicle treated), estrogen treatment followed by MSIR (estrogen treated), HTS treatment and MSIR (HTS treated), and combined treatment of estrogen plus HTS and MSIR (combined treated). In MSIR, mice were subjected to mesenteric ischemia for 60 min followed by reperfusion for 30 min. The histology of the lung and the gut was obtained. Lung injury was evaluated by lung edema and myeloperoxidase (MPO) activity; lung protein expression of macrophage migration inhibitory factor (MIF), toll-like receptor-4 (TLR4), phosphorylated inhibitory κBα (p-IκBα), and inducible nitric oxide synthetase (iNOS) were assayed. Survival analysis was monitored after MSIR for 120 min. Compared with those in the sham-treated group, the lung water ratio, MPO activity, and expressions of MIF, TLR4, p-IκBα, and iNOS were significantly increased in the vehicle-treated group. Diminished MIF, TLR4, p-IκBα, and iNOS expressions were found in the estrogen-treated group, whereas suppression of p-IκBα and iNOS was found in the HTS-treated group. Treatment with estrogen or HTS decreased the lung water and MPO activity. The combined treatment of estrogen and HTS further significantly diminished p-IκBα and iNOS expression, lung edema, and MPO activity and improved the inflammation of the lung and the morphology of the gut in histology compared with the results of a single treatment of estrogen or HTS. Survival analysis showed significantly increased survival in the combination-treated group compared with survival in the HTS-treated group. In conclusion, compared with single-agent use, treatment combining estrogen and HTS further decreases lung p-IκBα and iNOS expressions, as well as the degree of lung injury. These effects may result in better rates of survival from MSIR injury.

Hypertonic saline enhances host defense and reduces apoptosis in burn mice by increasing toll-like receptors

Hypertonic saline (HTS) is useful in the management of intracranial hypertension and shock patients. The aim of this study was to investigate whether HTS enhances host defense in burn mice through the increase of Toll-like receptors (TLRs) and nuclear factor κB (NF-κB) activation. C57BL/6, TLR4, C3H/HeN, and C3H/HeJ (nonfunctional TLR4 mutant) mice underwent burn and were given 10 mL/kg HTS (7.5% NaCl, 1.28 mol/L), 10 mL/kg saline (154 mmol/L), or 80 mL/kg saline (154 mmol/L) at 8 h after burn. At 24 h after burn, mesenteric lymph nodes were harvested and assayed for bacterial translocation (BT). Next, animals received i.p. Escherichia coli challenge, and bacterial clearance was measured. Finally, peritoneal cells were isolated for assay of bacterial killing activity, phagocytic activity, apoptotic ratio, NF-κB DNA binding activity, and expression of TLR4, MyD88, p-Akt, pp38, macrophage inflammatory protein 2, and Bcl-xL. Hypertonic saline decreased BT in C57BL/6 and C3H/HeN mice but not in TLR4 mutant mice. Also, HTS increased bacterial clearance and bacterial killing activity and decreased apoptotic ratio of peritoneal cells from C57BL/6 and C3H/HeN mice but not TLR4 or C3H/HeJ mice. Finally, HTS increased NF-κB activity and expression of TLR4, MyD88, p-Akt, pp38, macrophage inflammatory protein 2, and Bcl-xL in C57BL/6 but not in TLR4 mice. Hypertonic saline increases bacterial clearance and bacterial killing activity and decreases thermal injury-induced BT in wild-type but not in TLR4 mutant mice. Given that HTS induces NF-κB activity and TLR4, MyD88, and pp38 expression but decreases the apoptosis of inflammatory cells, we conclude that HTS resuscitation enhances host defense against bacterial challenge and reduces apoptosis of inflammatory cells in burn mice by increasing TLR4 expression and NF-κB activation.

Acute pancreatitis: hypertonic saline increases heat shock proteins 70 and 90 and reduces neutrophil infiltration in lung injury

OBJECTIVES

Acute pancreatitis (AP) protease release induces lung parenchymal destruction via matrix metalloproteinases (MMPs), a neutrophil (polymorphonuclear leukocyte)-dependent process. Recent studies in hemorrhagic shock revealed that hypertonic saline (HTS) has an anti-inflammatory effect and can inhibit a variety of neutrophil functions. The aim of this study was to determine whether HTS and its actions in the pathway of neutrophil migration, MMPs, and heat shock proteins (HSPs) are effective in protecting the lung from injury associated with AP.

METHODS

We determined neutrophil infiltration and expressions of MMPs and HSPs in the lung tissue after AP induced by retrograde infusion of 2.5% of sodium taurocholate.

RESULTS

Animals submitted to AP that received HTS compared with those who received normal saline presented with increased HSP70 and HSP90 expressions and reduced myeloperoxidase levels and MMP-9 expression and activity.

CONCLUSIONS

Our data raised the hypothesis that a sequence of HTS lung protection events increases HSP70 and HSP90, inhibiting infiltration of neutrophils and their protease actions in the lung.

The use of hypertonic saline for fluid resuscitation in sepsis: a review

Early volume resuscitation of a patient with sepsis has been shown to reduce morbidity, mortality, and healthcare resource consumption. Hypertonic saline offers a theoretically viable option for volume resuscitation. This article reviews the current information available regarding fluid resuscitation in patients with sepsis, with emphasis on the use of hypertonic saline.

Hypertonic saline resuscitation from hemorrhagic shock does not impair the neutrophil response to intraabdominal infection

BACKGROUND

Hypertonic saline (HTS) has been proposed as a resuscitation strategy following trauma based on its ability to prevent organ dysfunction by exerting immunosuppressive effects on inflammatory cells, including neutrophils. Because these cells are central to the innate response to bacteria, we hypothesized that hypertonic treatment for hemorrhagic shock might alter the host response to bacterial contamination of the peritoneal cavity and therefore render the host more susceptible to invasive infection.

METHODS

Male Sprague-Dawley rats were subjected to hemorrhagic shock and resuscitated with either lactated Ringer solution (RL) or HTS. After intraperitoneal injection of feces, Escherichia coli, or lipopolysaccharide, peritoneal neutrophil accumulation and bacterial clearance were studied. In some studies, lipopolysaccharide as an inflammatory stimulus was injected into both the peritoneal cavity and the lungs.

RESULTS

Peritoneal neutrophil accumulation in response to each of the stimuli did not differ between RL- and HTS-resuscitated animals. Whereas emigration into the peritoneum activated neutrophils, there was no difference between resuscitation strategies, consistent with the finding that bacterial clearance did not differ between groups. Although peritoneal neutrophil sequestration was unaffected by resuscitation type, HTS still was able to prevent lung neutrophil accumulation compared to RL treatment.

CONCLUSIONS

HTS resuscitation did not impair the host response to bacterial contamination of the peritoneal cavity. However, the ability of HTS to prevent lung neutrophil accumulation in this setting persisted. These findings suggest that peritoneal bacterial contamination should not be considered a contraindication to the use of HTS in the trauma setting associated with hemorrhagic shock.

Therapeutic effects of hypertonic saline on peritonitis-induced septic shock with multiple organ dysfunction syndrome in rats

OBJECTIVE

Significant mortality in patients with sepsis results from the development of multiple organ dysfunction syndrome. Small-volume resuscitation with 7.5% NaCl hypertonic saline has been proposed to restore physiologic hemodynamics in hemorrhagic shock. Therefore, we hypothesized that hypertonic saline resuscitation could alleviate the development of multiple organ dysfunction syndrome in sepsis induced by cecal ligation and puncture.

DESIGN

Randomized, prospective animal experiment.

SETTING

Academic research laboratory.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

The animals were randomly allocated to one of four groups: 1) sham operation (0.9% NaCl, 4 mL/kg intravenously, at 3 hrs after laparotomy); 2) sham operation plus hypertonic saline (7.5% NaCl, 4 mL/kg intravenously, at 3 hrs after laparotomy); 3) cecal ligation and puncture (0.9% NaCl, 4 mL/kg intravenously, at 3 hrs after cecal ligation and puncture); and 4) cecal ligation and puncture plus hypertonic saline (7.5% NaCl, 4 mL/kg intravenously, at 3 hrs after cecal ligation and puncture).

MEASUREMENTS AND MAIN RESULTS

Cecal ligation and puncture for 18 hrs was associated with circulatory failure (i.e., hypotension and vascular hyporeactivity to norepinephrine), multiple organ dysfunction syndrome (examined by biochemical variables and histologic studies), and 18-hr mortality. Hypertonic saline not only ameliorated the deterioration of hemodynamic changes but also attenuated neutrophil infiltration in the lung and the liver of septic animals. Hypertonic saline increased the survival rate at 9 and 18 hrs compared with the cecal ligation and puncture group. Moreover, hypertonic saline reduced plasma nitric oxide and interleukin-1beta and organ O2-* levels in rats that underwent cecal ligation and puncture.

CONCLUSIONS

Hypertonic saline prevented circulatory failure, alleviated multiple organ dysfunction syndrome, and decreased the mortality rate in animals receiving cecal ligation and puncture. These beneficial effects of hypertonic saline may be attributed to reducing the plasma concentration of nitric oxide and interleukin-1beta as well as the organ O2-* level and decreasing lung neutrophil infiltration and liver necrosis. Our study suggests that hypertonic saline could be a potential and inexpensive therapeutic agent in the early sepsis of animals or patients.

Gastrointestinal perfusion in septic shock

Septic shock is characterised by vasodilation, myocardial depression and impaired microcirculatory blood flow, resulting in redistribution of regional blood flow. Animal and human studies have shown that gastrointestinal mucosal blood flow is impaired in septic shock. This is consistent with abnormalities found in many other microcirculatory vascular beds. Gastrointestinal mucosal microcirculatory perfusion deficits have been associated with gut injury and a decrease in gut barrier function, possibly causing augmentation of systemic inflammation and distant organ dysfunction. A range of techniques have been developed and used to quantify these gastrointestinal perfusion abnormalities. The following techniques have been used to study gastrointestinal perfusion in humans: tonometry, laser Doppler flowmetry, reflectance spectrophotometry, near-infrared spectroscopy, orthogonal polarisation spectral imaging, indocyanine green clearance, hepatic vein catheterisation and measurements of plasma D-lactate. Although these methods share the ability to predict outcome in septic shock patients, it is important to emphasise that the measurement results are not interchangeable. Different techniques measure different elements of gastrointestinal perfusion. Gastric tonometry is currently the most widely used technique because of its non-invasiveness and ease of use. Despite all the recent advances, the usefulness of gastrointestinal perfusion parameters in clinical decision-making is still limited. Treatment strategies specifically aimed at improving gastrointestinal perfuision have failed to actually correct mucosal perfusion abnormalities and hence not shown to improve important clinical endpoints. Current and future treatment strategies for septic shock should be tested for their effects on gastrointestinal perfusion; to further clarify its exact role in patient management, and to prevent therapies detrimental to gastrointestinal perfusion being implemented.

Advances in burn care

PURPOSE OF REVIEW

This article reviews and critiques new developments in the critical care of burn patients.

RECENT FINDINGS

The practice of restrictive transfusion is slowly gaining traction. Abdominal compartment syndrome is associated with resuscitation volumes of 300 ml/kg per 24 h, and percutaneous decompression may be a treatment option. Adrenal insufficiency is common, but whom and when to treat are unclear. Imaging or noninvasive monitoring may confirm renal perfusion before urine output, and the concept of permissive hypovolemia should be explored. There is progress in the laboratory in smoke inhalation and myocardial depression, but no human translation. Antibiotic pharmacokinetics in large burns are unpredictable, and so aminoglycosides (measurable concentrations) are not obsolete. Selective digestive decontamination remains controversial. Nutritional predictions by formula are inaccurate. Oxandrolone is safe and effective in promoting anabolism in large burns. Deep venous thrombosis prophylaxis remains guided only by expert opinion. Females fare worse than male patients after burns.

SUMMARY

The application of the scientific method to burn care is improving slowly. Randomized controlled trials are becoming more common. There is a need for translation of excellent animal work to the human arena.