Endotoxin-induced lung inflammation is independent of the complement membrane attack complex

Circulating Complement C3-Alpha Chain Levels Predict Survival of Septic Shock Patients

BACKGROUND

Circulating complement C3 fragments released during septic shock might contribute to the development of complications such as profound hypotension and disseminated intravascular coagulation. The role of C3 in the course of septic shock varies in the literature, possibly because circulating C3 exists in different forms indistinguishable via traditional ELISA-based methods. We sought to test the relationship between C3 forms, measured by Western blotting with its associated protein size differentiation feature, and clinical outcomes.

METHODS

Secondary analysis of two prospective cohorts of patients with septic shock: a discovery cohort of 24 patents and a validation cohort of 181 patients. C3 levels were measured by Western blotting in both cohorts using blood obtained at enrollment. Differences between survivors and non-survivors were compared, and the independent prognostic values of C3 forms were assessed.

RESULTS

In both cohorts there were significantly lower levels of the C3-alpha chain in non-survivors than in survivors, and persisted after controlling for sequential organ failure assessment score. Area under the receiver operating characteristics to predict survival was 0.65 (95% confidence interval: 0.56-0.75). At a best cutoff value (Youden) of 970.6 μg/mL, the test demonstrated a sensitivity of 68.5% and specificity of 61.5%. At this cutoff point, Kaplan-Meier survival analysis showed that patients with lower levels of C3-alpha chain had significantly lower survival than those with higher levels (P < 0.001).

CONCLUSION

Circulating C3-alpha chain levels is a significant independent predictor of survival in septic shock patients.

Complement C6 deficiency exacerbates pathophysiology after spinal cord injury

Historically, the membrane attack complex, composed of complement components C5b-9, has been connected to lytic cell death and implicated in secondary injury after a CNS insult. However, studies to date have utilized either non-littermate control rat models, or mouse models that lack significant C5b-9 activity. To investigate what role C5b-9 plays in spinal cord injury and recovery, we generated littermate PVG C6 wildtype and deficient rats and tested functional and histological recovery after moderate contusion injury using the Infinite Horizon Impactor. We compare the effect of C6 deficiency on recovery of locomotor function and histological injury parameters in PVG rats under two conditions: (1) animals maintained as separate C6 WT and C6-D homozygous colonies; and (2) establishment of a heterozygous colony to generate C6 WT and C6-D littermate controls. The results suggest that maintenance of separate homozygous colonies is inadequate for testing the effect of C6 deficiency on locomotor and histological recovery after SCI, and highlight the importance of using littermate controls in studies involving genetic manipulation of the complement cascade.

Anti-inflammatory and antioxidant effect of cerium dioxide nanoparticles immobilized on the surface of silica nanoparticles in rat experimental pneumonia

A massage with the potent counter-inflammatory material, cerium dioxide nanoparticles, is promising and the antioxidant properties of CeO₂ are considered the main, if not the only, mechanism of this action. Nevertheless, the elimination of ceria nano-particles from the organism is very slow and there is a strong concern for toxic effect of ceria due to its accumulation. To overcome this problem, we engineered a combined material in which cerium nanoparticles were immobilized on the surface of silica nanoparticles (CeO₂ NP), which is shown to be easily removed from an organism and could be used as carriers for nano-ceria. In our study particle size was 220±5nm, Zeta-potential -4.5mV (in water), surface charge density -17.22μC/cm² (at pH 7). Thirty-six male Wistar rats, 5 months old and 250-290g were divided into four groups: 1) control; 2) CeO₂ NP treatment; 3) experimental pneumonia (i/p LPS injection, 1mg/kg); and 4) experimental pneumonia treated with CeO₂ NP (4 times during the study in dosage of 0.6mg/kg with an orogastric catheter). Gas exchange and pulmonary ventilation were measured four times: 0, 1, 3 and 24h after LPS injection in both untreated and CeO₂ NP-treated animals. The mRNA of TNF-α, Il-6, and CxCL2 were determined by RT-PCR. ROS-generation in blood plasma and lung tissue homogenates were measured by means of lucigenin- and luminol-enhanced chemiluminescence. Endotoxemia in the acute phase was associated with: (1) pathological changes in lung morphology; (2) increase of ROS generation; (3) enhanced expression of CxCL2; and (4) a gradual decrease of VO₂ and V_E. CeO2 NP treatment of intact animals did not make any changes in all studied parameters except for a significant augmentation of VO₂ and V_E. CeO₂ NP treatment of rats with pneumonia created positive changes in diminishing lung tissue injury, decreasing ROS generation in blood and lung tissue and decreasing pro-inflammatory cytokine expression (TNF-α, Il-6 and CxCL2). Oxygen consumption in this group was increased compared to the LPS pneumonia group. In our study we have shown anti-inflammatory and antioxidant effects of CeO₂ NP. In addition, this paper is the first to report that CeO₂ NP stimulates oxygen consumption in both healthy rats, and rats with pneumonia. We propose the key in understanding the mechanisms behind the phenomena lies in the property of CeO₂ NP to scavenge ROS and the influence of this potent antioxidant on mitochondrial function. The study of biodistribution and elimination of СеО₂NP is the purpose of our ongoing study.

Febuxostat protects rats against lipopolysaccharide-induced lung inflammation in a dose-dependent manner

The aim of the present work was to investigate possible protective effects of febuxostat, a highly potent xanthine oxidase inhibitor, against acute lung injury (ALI) induced by lipopolysaccharide (LPS) in rats. Male Sprague Dawley rats were randomly divided into six groups, as follows: (i) vehicle control group; (ii) and (iii) febuxostat 10 and febuxostat 15 groups, drug-treated controls; (iv) LPS group, receiving an intraperitoneal injection of LPS (7.5 mg/kg); (v) and (vi) febuxostat 10-LPS and febuxostat 15-LPS groups, receiving oral treatment of febuxostat (10 and 15 mg/kg/day, respectively) for 7 days before LPS. After 18 h administration of LPS, blood was collected for C-reactive protein (CRP) measurement. Bronchoalveolar lavage fluid (BALF) was examined for leukocyte infiltration, lactate dehydrogenase (LDH) activity, protein content, and total nitrate/nitrite. Lung weight gain was determined, and lung tissue homogenate was prepared and evaluated for oxidative stress. Tumor necrosis factor-α (TNF-α) was assessed in BALF and lung homogenate. Moreover, histological changes of lung tissues were evaluated. LPS elicited lung injury characterized by increased lung water content (by 1.2 fold), leukocyte infiltration (by 13 fold), inflammation and oxidative stress (indicated by increased malondialdehyde (MDA), by 3.4 fold), and reduced superoxide dismutase (SOD) activity (by 34 %). Febuxostat dose-dependently decreased LPS-induced lung edema and elevations in BALF protein content, infiltration of leukocytes, and LDH activity. Moreover, the elevated levels of TNF-α in BALF and lung tissue of LPS-treated rats were attenuated by febuxostat pretreatment. Febuxostat also displayed a potent antioxidant activity by decreasing lung tissue levels of MDA and enhancing SOD activity. Histological analysis of lung tissue further demonstrated that febuxostat dose-dependently reversed LPS-induced histopathological changes. These findings demonstrate a significant dose-dependent protection by febuxostat against LPS-induced lung inflammation in rats.

The role of complement system in septic shock

Septic shock is a critical clinical condition with a high mortality rate. A better understanding of the underlying mechanisms is important to develop effective therapies. Basic and clinical studies suggest that activation of complements in the common cascade, for example, complement component 3 (C3) and C5, is involved in the development of septic shock. The involvement of three upstream complement pathways in septic shock is more complicated. Both the classical and alternative pathways appear to be activated in septic shock, but the alternative pathway may be activated earlier than the classical pathway. Activation of these two pathways is essential to clear endotoxin. Recent investigations have shed light on the role of lectin complement pathway in septic shock. Published reports suggest a protective role of mannose-binding lectin (MBL) against sepsis. Our preliminary study of MBL-associated serine protease-2 (MASP-2) in septic shock patients indicated that acute decrease of MASP-2 in the early phase of septic shock might correlate with in-hospital mortality. It is unknown whether excessive activation of these three upstream complement pathways may contribute to the detrimental effects in septic shock. This paper also discusses additional complement-related pathogenic mechanisms and intervention strategies for septic shock.

Central role of complement membrane attack complex in monosodium urate crystal-induced neutrophilic rabbit knee synovitis

OBJECTIVE

Monosodium urate monohydrate (MSU) crystals promote gouty inflammation that is critically mediated by neutrophil recruitment and activation. Interleukin-8 (IL-8) and closely related chemokines are major neutrophil chemotaxins in experimental gout. But MSU crystals also activate the classical and alternative pathways of complement, and MSU crystals directly cleave C5 on the crystal surface. Unlike IL-8, the roles in acute gout of individual complement-derived peptides and of the terminal C5b-9 complement components that comprise the membrane attack complex (MAC) are unclear. Hence, we studied rabbits deficient in the MAC component C6 to determine if MAC mediated urate crystal-induced arthritis.

METHODS

We injected C6-deficient and C6-sufficient rabbit knee joints with 10 mg of pyrogen-free urate crystals and analyzed IL-8 levels, leukocyte influx, and joint inflammation 24 hours later.

RESULTS

There was a significant decrease (>60%) in swelling in MSU crystal-injected knees of C6-deficient animals as compared with C6-sufficient animals (P < 0.05). An attenuated rise in MSU crystal-induced joint effusion levels of IL-8 also was observed, which was concordant with diminished numbers of neutrophils (P < 0.05) but not monocytes in MSU crystal-induced knee synovial fluid from C6-deficient animals. Synovial tissue analysis confirmed mononuclear leukocyte infiltration in response to MSU crystal injection in all animals, but substantial neutrophil infiltration only in C6-sufficient animals.

CONCLUSION

MAC activation appears to play a major role in intraarticular IL-8 generation and in neutrophil recruitment in experimental acute gouty arthritis of the rabbit knee. C6 and MAC activation may represent novel therapeutic targets for suppression of neutrophil-mediated joint inflammation in gout.

Pulmonary toxicity of dust generated during weaving of carpets

The dust generated during weaving (carpet dust) tibbati, knotted and tuffted carpets in carpet industry was studied for its toxicity in vitro and in vivo. Carpet dust (0.5, 1.0, 2.5 and 5.0 mg/1 x 10(6) cells) caused in vitro cytotoxicity in rat alveolar macrophages (AM) in a concentration-dependent manner. The cytotoxic, inflammatory and oxidative responses were observed in bronchoalveolar lavage fluid (BALF) of rats at 1, 4, 8 and 16 days after exposure. Rats were intratracheally exposed at 5 mg/rat individually to all three types of carpet dust. All types of carpet dusts produced increased AM, lymphocytes (PMN) population in BALF suggesting their inflammatory reactions. Cytotoxic nature of carpet dust was shown by the increased activities of lactate dehydrogenase (LDH) and acid phosphatase (AP) in BALF. Increased AM population and in vitro cytotoxicity due to carpet dusts have shown some correlation with the levels of LDH and AP activities in BALF. The gradual enhanced profile of hydrogen peroxide (H2O2) and nitric oxide (NO) along with depletion of reduced glutathione (GSH) in AM due to these carpet dusts are suggestive of their oxidant nature. The enzyme activities of both glutathione peroxidase (GPx) and glutathione reductase (GR) in AM were marginally reduced in exposed rats. In conclusion, the data suggest the cytotoxic, inflammatory and oxidant nature of carpet dusts. It is extrapolated that health effects on carpet weavers would be associated with the concentration and nature of airborne dust generated during weaving of carpets.

Does endotoxin-activated complement alter myocellular sodium homeostasis during sepsis?

BACKGROUND

Inappropriate complement activation is closely related to tissue injury and organ dysfunction during systemic infection. It is not clear, however, if endotoxin-induced complement activation is responsible for changes in myocellular sodium homeostasis during sepsis.

METHODS

Rats underwent cecal ligation and puncture (CLP) or sham operation. Twenty-four hours after operation, fast-twitch extensor digitorum longus (EDL) muscles were isolated, incubated at 30 degrees C for 1 hour in Krebs-Henseleit buffer (KHB) (pH 7.4), and used to measure intracellular Na+ and K+ contents. Blood samples were collected to measure serum hemolytic complement activity and endotoxin levels. In addition, EDL muscles isolated from normal animals were incubated at 30 degrees C for 1 hour with zymosan-activated (10 mg/mL at 37 degrees C for 1 hour) rat sera, with lipopolysaccharide (LPS)-activated (LPS from Escherichia coli 055:B5, 10 or 200 microg/mL at 37 degrees C for 30 minutes) rat sera, with heat-inactivated (56 degrees C for 30 minutes) rat sera, with LPS (1 or 20 microg/mL), or in KHB. EDL muscles isolated from normal animals were also incubated with septic sera collected 6 or 24 hours after CLP with or without administration of soluble complement receptor type 1 (20 mg/kg, intraperitoneally). Myocellular Na+ and K+ contents ([Na+]i and [K+]i) were assayed using "washout" technique. Soluble C5b-9 complex levels in zymosan-activated or LPS-activated human sera were determined by enzyme-linked immunosorbent assay to evaluate the degree of complement activation induced by zymosan or LPS.

RESULTS

Myocellular [Na+]i and [Na+]i/[K+]i ratios increased significantly 24 hours after CLP as compared with sham operation and were associated with decreased serum hemolytic complement activity and increased serum endotoxin levels. Zymosan-activated rat sera at sublytic concentrations markedly increased [Na+]i and [Na+]i/[K+]i ratios in isolated EDL muscles relative to heat-inactivated rat sera. LPS-activated rat sera, however, did not alter these two indices. In addition, myocellular [Na+]i and [Na+]i/[K+]i ratios were equivalent among normal EDL muscles incubated with septic sera, soluble complement receptor type 1-treated septic sera, or KHB.

CONCLUSION

These results collectively suggest that polymicrobial sepsis, as produced by CLP, alters sodium homeostasis in fast-twitch skeletal muscles in association with changes in systemic complement activation and circulating endotoxin levels. Although endotoxin can activate the complement cascade, endotoxin-induced complement activation does not appear to be responsible for changes in myocellular sodium homeostasis observed during sepsis in rats.

Endotoxin-stimulated innate immunity: A contributing factor for asthma

Exposure to airborne endotoxin in infancy may protect against asthma by promoting enhanced T(H)1 response and tolerance to allergens. On the other hand, later in life, it adversely affects patients with asthma. Endotoxin binding to receptors on macrophages and other cells generates IL-12, which inhibits IgE responses. It also generates cytokines like IL-1, TNF-alpha, and IL-8, which cause inflammation. These signal transduction pathways resemble those leading to the generation of cytokines, such as IL-4, IL-13, and IL-5, which are responsible for the inflammation of IgE-mediated allergic disease. The main difference seems to be that endotoxin recruits neutrophils, but IgE recruits eosinophils, and the details of the tissue injury from these granulocytes differ. Sources of airborne endotoxin include many agricultural dusts, aerosols from contaminated water in many industrial plants, contaminated heating and air-conditioning systems, mist-generating humidifiers, and damp or water-damaged homes. Acute inhalation of high concentrations of endotoxin can cause fever, cough, and dyspnea. Chronic inhalation of lesser amounts causes chronic bronchitis and emphysema and is associated with airway hyperresponsiveness. Airborne endotoxin adversely affects patients with asthma in 3 ways: (1) by increasing the severity of the airway inflammation; (2) by increasing the susceptibility to rhinovirus-induced colds; and (3) by causing chronic bronchitis and emphysema with development of irreversible airway obstruction after chronic exposure of adults. The most effective management is mitigating exposure. The potential of drug treatments requires further clinical investigation.

Animal models of inherited complement deficiency

The initial description of murine strains deficient in complement component C5 has been followed by the recognition in a range of animal species of a variety of natural complement component deficiencies, many of which have been characterized at the molecular level. The use of such species in inflammatory and infectious experimental models has led to significant progress in understanding the role of specific complement factors (and pathways) in disease pathogenesis. Deficiencies of early complement factors are characterized by impairment of immune response, possibly due to defective processing of immune complexes. Complete (but not partial) deficiency of the central component C3 predisposes affected animals to significant risk of infection and renal disease. Studies in species deficient in the terminal pathway component C6 are particularly relevant for investigating the pathogenetic role of the terminal membrane attack complex (MAC), implicating it as a causative agent in diverse inflammatory insults such as reperfusion injury, glomerular damage, and xenograft hyperacute rejection. Further investigations in such naturally deficient strains, added to results derived from studies in knockout animals, are likely to expand our understanding of the role of the activated complement system in experimental inflammatory disease, with significant potential implications for the treatment of human disease.

Priming of alveolar macrophages by leukotriene D(4): potentiation of inflammation

Cysteinyl leukotrienes (LTs), including LTC(4), LTD(4), and LTE(4), are well known to induce bronchoconstriction and increase bronchial hyperreactivity, mucus secretion, and vascular permeability. Interestingly, alveolar macrophages (AMs) express LTD(4) high-affinity receptor. These cells represent a major source of inflammatory mediators implicated in the pathophysiology of asthma. Thus, we investigated the immunomodulatory effects of LTD(4) on the production of inflammatory mediators such as macrophage inflammatory protein (MIP)- 1alpha, tumor necrosis factor (TNF), and nitric oxide (NO) by AMs. NR8383 cells, an AM cell line, were pretreated with LTD(4) (10(-11) M) for different periods of time and stimulated or not with lipopolysaccharide (LPS) for 2 h. Although LTD(4) treatment did not modulate the release of MIP-1alpha and TNF, this treatment (6 h) significantly increased the release of these mediators when AMs were further stimulated with LPS (increases of 47 and 21%, respectively). Further, LTD(4) pretreatment increased messenger RNA (mRNA) levels of MIP-1alpha and TNF. These effects of LTD(4) were abrogated by the presence of a LTD(4) receptor antagonist, Verlukast (MK-679), showing the specificity of LTD(4). Interestingly, LTD(4) treatment significantly increased the release of NO by LPS-stimulated AMs without modulating mRNA levels of the inducible NO synthase. Our data suggest that LTD(4) primes AMs to release more MIP-1alpha, TNF, and NO after stimulation. Thus, in addition to its potent bronchoconstrictor effect, LTD(4) may participate in the inflammatory process seen in asthma by potentiating the production of proinflammatory mediators by AMs during immunologic stimuli.