Erythropoietin Exacerbates Inflammation and Increases the Mortality of Histoplasma capsulatum-Infected Mice

Erythropoietin prevents LPS-induced preterm birth and increases offspring survival

Problem

Preterm delivery is the leading cause of neonatal mortality and contributes to delayed physical and cognitive development in children. At present, there is no efficient therapy to prevent preterm labor. A large body of evidence suggests that infections might play a significant and potentially preventable cause of premature birth. This work assessed the effects of erythropoietin (EPO) in a murine model of inflammation‐associated preterm delivery, which mimics central features of preterm infections in humans.

Method of study

BALB/c mice were injected i.p. with 20 000 IU/kg EPO or normal saline twice on gestational day (GD) 15, with a 3 hours time interval between injections. An hour after the first EPO or normal saline injection, all mice received two injections of 50 μg/kg LPS, also given 3 hours apart.

Results

EPO significantly prevented preterm labor and increased offspring survival in an LPS induced preterm delivery model. EPO prevented LPS‐induced leukocyte infiltration into the placenta. Moreover, EPO inhibited the expression of pro‐inflammatory cytokines, interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6), and tumour necrosis factor‐α (TNF‐α) in maternal serum and amniotic fluid. EPO also prevented LPS‐induced increase in placental prostaglandin (PG)E2 and uterine inducible nitric oxide synthase (iNOS) production, while decreasing nuclear factor kappa‐B (NF‐κβ) activity in the myometrium. EPO also increased the gene expression of placental programmed cell death ligand 1 (PD‐L1) in LPS‐treated mice.

Conclusions

Our results suggest that EPO could be a potential novel therapeutic strategy to tackle infection‐related preterm labor.

IL-22 Promotes IFN-γ-Mediated Immunity against Histoplasma capsulatum Infection

Histoplasma capsulatum is the agent of histoplasmosis, one of the most frequent mycoses in the world. The infection initiates with fungal spore inhalation, transformation into yeasts in the lungs and establishment of a granulomatous disease, which is characterized by a Th1 response. The production of Th1 signature cytokines, such as IFN-γ, is crucial for yeast clearance from the lungs, and to prevent dissemination. Recently, it was demonstrated that IL-17, a Th17 signature cytokine, is also important for fungal control, particularly in the absence of Th1 response. IL-22 is another cytokine with multiple functions on host response and disease progression. However, little is known about the role of IL-22 during histoplasmosis. In this study, we demonstrated that absence of IL-22 affected the clearance of yeasts from the lungs and increased the spreading to the spleen. In addition, IL-22 deficient mice (Il22-/-) succumbed to infection, which correlated with reductions in the numbers of CD4+ IFN-γ+ T cells, reduced IFN-γ levels, and diminished nitric oxide synthase type 2 (NOS2) expression in the lungs. Importantly, treatment with rIFN-γ mitigated the susceptibility of Il22-/- mice to H. capsulatum infection. These data indicate that IL-22 is crucial for IFN-γ/NO production and resistance to experimental histoplasmosis.

Paradoxical Effect of LTB4 on the Regulation of Stress-Induced Corticosterone Production

Depression is a mental illness with a complex and multifactorial etiology, which has been associated with stress and inflammation. Infections, autoimmune diseases, envenomation, and trauma induce an inflammatory response that is characterized by increasing levels of circulating cytokines (e.g., IL-1β) and lipid mediators [e.g., PGE₂ and leukotrienes B₄ (LTB₄)]. Recently, we showed that LTB₄ production by the 5-lipoxygenase (5-LO) pathway regulates IL-1β and PGE₂ release, reducing tissue damage in a model of sterile inflammation. Since IL-1β and PGE₂ increase in serum of stressed patients and potentially trigger depression, we used an animal model of chronic unpredictable stress (CUS) to investigate the potential impact of LTB₄ over depression-like symptoms. At basal conditions, 5-LO deficiency (Alox5^−/−) reduces the preference for sucrose, while inducing a higher immobilization time on the tail suspension test when compared 129sv. Moreover, Alox5^−/− mice present increased caspase-1 expression and elevated levels of IL-1β, IL-17 and PGE₂ in the spleen, with increasing corticosterone levels in the frontal cortex but reducing systemic levels. Compared to 129sv mice, CUS induced higher levels of systemic, frontal cortex and hippocampal corticosterone, and also reduced sucrose preference, increased levels of splenic IL-1β, IL-17 and PGE₂ and reduced levels of LTB₄. Interestingly, CUS exposure did not alter the reduced sucrose preference shown by Alox5^−/− mice but greatly enhanced splenic PGE₂ production. Compared to Alox5^−/− mice at basal conditions, CUS exposure also increased levels of systemic corticosterone, which remained lower than those of CUS-129sv animals. We also observed that treatment with LTB₄ decreased caspase-1 expression and systemic levels of corticosterone in CUS-Alox5^−/− mice but there was no significant impact on the reduced sucrose preference. Our results demonstrate that LTB₄ controls the hypothalamic-pituitary-adrenal (HPA) axis by regulating levels of systemic corticosterone associated with the repression of caspase-1 expression and production of inflammatory mediators. One limitation of our study is that 129sv and Alox5^−/− mice were not littermates, not sharing, therefore, the same intra-uterine and preweaning environment. Even so, taken together our results indicate that 5-LO activity is critical for the regulation of stress-induced symptoms, suggesting that the Alox5^−/− mouse could be a natural model of corticosterone-independent reduced reward sensitivity.

Dose-dependent exacerbation of ventilation-induced lung injury by erythropoietin in preterm newborn lambs

Erythropoietin (EPO) is being trialled in preterm infants to reduce brain injury, but high doses increase lung injury in ventilated preterm lambs. We aimed to determine whether early administration of lower doses of EPO could reduce ventilation-induced lung injury and systemic inflammation in preterm lambs. Ventilation was initiated in anaesthetized preterm lambs [125 ± 1 (SD) days gestation] using an injurious strategy for the first 15 min. Lambs were subsequently ventilated with a protective strategy for a total of 2 h. Lambs were randomized to receive either intravenous saline (Vent; n = 7) or intravenous 300 ( n = 5), 1,000 (EPO1000; n = 5), or 3,000 (EPO3000; n = 5) IU/kg of human recombinant EPO via an umbilical vein. Lung tissue was collected for molecular and histological assessment of inflammation and injury and compared with unventilated control lambs (UVC; n = 8). All ventilated groups had similar blood gas and ventilation parameters, but EPO1000 lambs had a lower fraction of inspired oxygen requirement and lower alveolar–arterial difference in oxygen. Vent and EPO lambs had increased lung interleukin (IL)-1β, IL-6, and IL-8 mRNA, early lung injury genes connective tissue growth factor, early growth response protein 1, and cysteine-rich 61, and liver serum amyloid A3 mRNA compared with UVCs; no difference was observed between Vent and EPO groups. Histological lung injury was increased in Vent and EPO groups compared with UVCs, but EPO3000 lambs had increased lung injury scores compared with VENT only. Early low-doses of EPO do not exacerbate ventilation-induced lung inflammation and injury and do not provide any short-term respiratory benefit. High doses (≥3,000 IU/kg) likely exacerbate lung inflammation and injury in ventilated preterm lambs.

NEW & NOTEWORTHY Trials are ongoing to assess the efficacy of erythropoietin (EPO) to provide neuroprotection for preterm infants. However, high doses of EPO increase ventilation-induced lung injury (VILI) in preterm lambs. We investigated whether early lower doses of EPO may reduce VILI. We found that lower doses did not reduce, but did not increase, VILI, while high doses (≥3,000 IU/kg) increase VILI. Therefore, lower doses of EPO should be used in preterm infants, particularly those receiving respiratory support.

Telfairia occidentalis Hook.f. - associated haematopoietic effect is mediated by cytokines but independent of testosterone: A preliminary report

ETHNOPHARMACOLOGICAL RELEVANCE

Telfairia occidentalis Hook.f. (TO) is popular in Nigeria for the ethnopharmacological use of its leaves to improve haematological parameters in normal and anaemic subjects. Cytokines are well-known to regulate haematopoiesis. However, their involvement in TO-associated haematopoietic effect is not known and necessitated this study.

MATERIALS AND METHODS

Twenty-five (25) male rats were randomly divided into 3 oral treatment groups as follows: Group 1 (control, n=5) received 0.2 ml/kg normal saline for 14 days. Groups 2 and 3 (n= 10 each) were subdivided into 2 (n=5) and received 100 mg/kg and 200 mg/kg of aqueous extract of TO respectively for 7 or 14 days.

RESULTS

TO had dose- and duration-dependent effects on the estimated parameters. Both doses of TO increased the RBC, WBC and erythropoietin concentrations at 14 but not 7 days. Moreover, its 100 mg/kg increased haemoglobin, neutrophil, and interleukin-3 concentrations at 7 days, while 200 mg/kg increased PCV and neutrophils at 14 days, lymphocytes at 7 days, and haemoglobin at both durations.

CONCLUSION

The haematopoietic effect of TO might be partly mediated by cytokines (interleukin-3 and erythropoietin) but independent of testosterone.