Pulmonary and muscle profile in pneumosepsis: A temporal analysis of inflammatory markers

In sepsis, greater understanding of the inflammatory mechanism involved would provide insights into the condition and into its extension to the muscular apparatus in critically ill patients. Therefore, this study evaluates the inflammatory profile of pneumosepsis induced by Klebsiella pneumoniae (K.p.) in lungs and skeletal muscles during the first 72 h. Male BALB/c mice were divided into 4 groups, submitted to intratracheal inoculation of K.p. at a concentration of 2 × 10⁸ (PS) or PBS, and assessed after 24 (PS24), 48 (PS48) and 72 (PS72) hours. The Maximum Physical Capacity Test (MPCT) was performed before and after induction. Pulmonary inflammation was assessed by total cell number, nitric oxide levels (NOx), IL-1β and TNF-α levels in bronchoalveolar lavage fluid (BALF); inflammation and muscle trophism were evaluated by the levels of TNF-α, IL-6, TGF-β and BDNF by ELISA and NF-κB by western blotting in muscle tissue. Cells and colony forming units (CFU) were also analyzed in blood samples. The PS groups showed an increase in total cells in the BALF (p < 0.05), as well in the number of granulocytes in the blood (p < 0.05) and a decrease in performance in the MPCT (p < 0.05). NOx levels showed significant increase in PS72, when compared to Control group (p = 0.03). The PS24 showed a significant increase lung in TNF-α levels (p < 0.001) and in CFU (p = 0.013). We observed an increase in muscular IL-6 and nuclear NF-κB levels in PS24 group, when compared to PS48 and Control groups (p < 0.05). Nevertheless, mild signs of injury in the skeletal muscle tissue does not support the idea of an early muscular injury in this experimental model, suggesting that the low performance of the animals during the MPCT may be related to lung inflammation.

Morphology of the Oligoryzomys nigripes respiratory system

Rodents are important in the transmission of infectious diseases that affect the respiratory tract, including simple infections and those caused by specific pathogens. These animals are natural reservoirs of zoonoses that cause many public health diseases. Basic knowledge on the morphology of these animals is important as basic research is useful for applied studies, such as the development of clinical, therapeutic, surgical and clinical models. Morphological data of respiratory tract in Oligoryzomys nigripes are absent in the literature. Therefore, the aim of this study was to perform a morphological analysis of the respiratory tract of O. nigripes. Five adult females from the environmental reserve in São Joaquim da Barra, São Paulo were used, donated to the Museum of Veterinary Anatomy (FMVZ/USP). Several morphological features follow the same pattern seen in rodents; however, this species showed some differences such as the presence of three lobar bronchi, nonlobed left lung and the right lung constituted by two lobes. Respiratory epithelium lined the whole respiratory tract and was seen using scanning electron microscopy the oval shape of the parenchyma and alveoli.

The route less taken: pulmonary models of enteric Gram-negative infection

Many pathogens are capable of causing a fulminant infection in pulmonary tissues of mammals. Animal models have provided an extensive understanding of the genetic and molecular mechanisms of bacterial pathogenesis as well as host immune response in the lungs. Many clinically relevant Gram-negative bacteria are host-restricted. Thus, the powerful, informative tools of mouse models are not available for study with these organisms. However, over the past 30 years, enterprising work has demonstrated the utility of pulmonary infection with enteric pathogens. Such infection models have increased our understanding host-pathogen interactions in these organisms. Here, we provide a review and comparison of lung models of infection with enteric, Gram-negative bacteria relative to naturally occurring lung pathogens.

Pneumonia-induced sepsis in mice: temporal study of inflammatory and cardiovascular parameters

The aim of the present work is to provide a better comprehension of the pneumonia-induced sepsis model through temporal evaluation of several parameters, and thus identify the main factors that determine mortality in this model. Klebsiella pneumoniae was inoculated intratracheally in anesthetized Swiss male mice. Inflammatory and cardiovascular parameters were evaluated 6, 24 and 48 h after the insult. The results show that severity of infection and the mortality correlated with the amount of bacteria. Six, 24 and 48 h after inoculation, animals presented pathological changes in lungs, increase in cell number in the bronchoalveolar lavage, leukopenia, increase in TNF-α and IL-1β levels, hypotension and hyporesponsiveness to vasoconstrictors, the two latter characteristics of severe sepsis and septic shock. Significant numbers of bacteria in spleen and heart homogenates indicated infection spreading. Interestingly, NOS-2 expression appeared late after bacteria inoculation, whereas levels of NOS-1 and NOS-3 were unchanged. The high NOS-2 expression coincided with an exacerbated NO production in the infection focus and in plasma, as judging by nitrate + nitrite levels. This study shows that K. pneumoniae inoculation induces a systemic inflammatory response and cardiovascular alterations, which endures at least until 48 h. K. pneumoniae-induced lung infection is a clinically relevant animal model of sepsis and a better understanding of this model may help to increase the knowledge about sepsis pathophysiology.

Induction of cytokines in different organs after intranasal inoculation of Campylobacter jejuni in mice

Background

Cytokine production and histopathological changes occur in the lungs of mice after intranasal inoculation with Campylobacter jejuni, but the levels of cytokines in different organs to which C. jejuni disseminates have not been studied.

Findings

Adult BALB/c mice were intranasally inoculated with C. jejuni 81–176 (test) or phosphate-buffered saline (control) (n=16 per group). The levels of cytokines in the organs (spleen, liver, and small and large intestines) to which C. jejuni disseminated were measured by ELISA. Two cytokine patterns were observed. First, increased proinflammatory cytokines, TNF-α, IL-1, and IL-2, were followed by anti-inflammatory cytokines, IL-4 and IL-10 in the spleen and large intestine. Second, in the liver and small intestine, there was a predominant production of anti-inflammatory cytokines, IL-4 and IL-10, with some increase in IL-2 levels. In the spleen and intestines, the levels of pro- and anti-inflammatory cytokines were concurrently increased.

Conclusion

Dissemination of C. jejuni is associated with the production of different cytokine profiles in different tissues, with the proinflammatory response appearing in the spleen and large intestine at an earlier time point than in the liver and small intestine. The organs produce different cytokine profiles in response to C. jejuni dissemination. These preliminary findings should be confirmed with a study involving a larger group of animals.

Correlation of proinflammatory and anti-inflammatory cytokine levels with histopathological changes in an adult mouse lung model of Campylobacter jejuni infection

Campylobacter jejuni is a major cause of diarrhea in humans. A mouse lung model of infection was previously established for C. jejuni. We used this model to study cytokine production in the lungs and correlated it with pathological changes. C. jejuni strain 81-176 or sterile phosphate-buffered saline was intranasally inoculated into adult BALB/c mice. The levels of proinflammatory cytokines (gamma interferon, tumor necrosis factor alpha, interleukin-1beta [IL-1beta], IL-2) and anti-inflammatory cytokines (IL-4, IL-10), in addition to those of IL-6, were assessed on days 1, 3, and 5 postinfection by enzyme-linked immunosorbent assay, and the ratios of proinflammatory cytokines to anti-inflammatory cytokines were calculated. Since IL-6 is unique in that it is both a proinflammatory cytokine and a TH2 cytokine, it was considered to be both in the determination of these ratios. The significance of the cytokine levels and ratios were determined by the Mann-Whitney U test (P<or=0.05). The induction of proinflammatory cytokines in the lungs of infected mice, as indicated by the cytokine levels and ratios, coincided with the accumulation of neutrophils and activated macrophages, in addition to the clearance of the bacterial load and bacteriumlike structures that we have previously shown in the same groups of mice. This was followed by increased levels of anti-inflammatory cytokines and the resolution of inflammation and pathology in the lungs. This study demonstrates the dynamics of cytokine production and their correlation with tissue inflammation and the resolution of infection. This model is useful for further studies of the pathogenesis of C. jejuni infection and vaccine evaluation.