Inhibition of Activin A suppressed tumor necrosis factor-α secretion and improved histopathological conditions in malarial mice

Malaria infection still remains as one of the most prominent parasitic diseases afflicting mankind in tropical and subtropical regions. The severity of malaria infection has often been associated to exuberant host immune inflammatory responses that could possibly lead to severe immunopathological conditions and subsequent death of host tissues. Activin A is a protein belonging to the transforming growth factor-beta (TGF-β) family that regulates multiple physiological processes and pathological-associated diseases. The biological roles of activin A have been associated with manipulation of inflammation-related processes and modulation of host immune responses. This implies that activin A protein could play a role in malaria pathogenesis since malaria infection has been closely linked to severe immune responses leading to death, However, the actual in vivo role of activin A in malaria infection remains elusive. Hence, this study was undertaken to investigate the involvement of activin A in malaria infection as well as to assess the modulating effects of activin A on the cytokine releases (TNF-α, IFN-γ and IL-10) and histopathological changes in major affected organs (kidney, liver, lung, brain and spleen) in malarial mice infected with Plasmodium berghei ANKA. Our results showed that the concentrations of plasma activin A were significantly increased in malarial mice throughout the study periods. Also. the systemic activin A level was positively correlated with malaria parasitemia. This indicates that activin A could play a role in malaria pathogenesis and malaria parasitemia development. Plasma TNF-α, IFN-γ and IL-10 cytokine levels were significantly increased in malarial mice at day-5 post infection, suggesting that these cytokines attributed to severe malaria pathogenesis. Histopathological features such as sequestration of parasitized red blood cells (pRBCs) and hemozoin formation were amongst the most common pathological conditions observed in tissues of major affected organs (kidney, liver, lung, brain and spleen) in malarial mice. Neutralization of activin A production via recombinant mouse activin RIIA Fc chimera (rmActivin RIIA Fc chimera) had significantly reduced the parasitemia levels in malarial mice. The release of TNF-α cytokine was significantly reduced as well as the sequestration of parasitized pRBCs and hemozoin formation in major affected organs in malarial mice were also alleviated following inhibition of activin A production. Overall, this preliminary study suggests that activin A could play an immune modulation role in malaria pathogenesis through modulation of TNF-α release that benefits host from severe pathological destructions provoked by intensified inflammatory responses. Further studies are warranted to elucidate the precise mechanism of immune modulation mediated by activin A and its associated immune-modulation mediators in regulating the inflammatory responses elicited during the course of malaria infection.

Weight loss after laparoscopic adjustable gastric band and resolution of the metabolic syndrome and its components

BACKGROUND

Substantial weight loss in the setting of obesity has considerable metabolic benefits. Yet some studies have shown improvements in obesity-related metabolic comorbidities with more modest weight loss. By closely monitoring patients undergoing bariatric surgery, we aimed to determine the effects of weight loss on the metabolic syndrome and its components and determine the weight loss required for their resolution.

METHODS

We performed a prospective observational study of obese participants with metabolic syndrome (Adult Treatment Panel III criteria) who underwent laparoscopic adjustable gastric banding. Participants were assessed for all criteria of the metabolic syndrome monthly for the first 9 months, then 3-monthly until 24 months.

RESULTS

There were 89 participants with adequate longitudinal data. Baseline body mass index was 42.4±6.2 kg m^-2 with an average age was 48.2±10.7 years. There were 56 (63%) women. Resolution of the metabolic syndrome occurred in 60 of the 89 participants (67%) at 12 months and 60 of the 75 participants (80%) at 24 months. The mean weight loss when metabolic syndrome resolved was 10.9±7.7% total body weight loss (TBWL). The median weight loss at which prevalence of disease halved was 7.0% TBWL (17.5% excess weight loss (EWL)) for hypertriglyceridaemia; 11% TBWL (26.1-28% EWL) for high-density lipoprotein cholesterol and hyperglycaemia; 20% TBWL (59.5% EWL) for hypertension and 29% TBWL (73.3% EWL) for waist circumference. The odds ratio for resolution of the metabolic syndrome with 10-12.5% TBWL was 2.09 (P=0.025), with increasing probability of resolution with more substantial weight loss.

CONCLUSIONS

In obese participants with metabolic syndrome, a weight loss target of 10-12.5% TBWL (25-30% EWL) is a reasonable initial goal associated with significant odds of having metabolic benefits. If minimal improvements are seen with this initial target, additional weight loss substantially increases the probability of resolution.

Interleukin-27 exhibited anti-inflammatory activity during Plasmodium berghei infection in mice

Interleukin-27 (IL-27) has a pleiotropic role either as a pro-inflammatory or anti-inflammatory cytokine in inflammatory related diseases. The role and involvement of IL-27 during malaria was investigated and the effects of modulating its release on the production of major inflammatory cytokines and the histopathological consequences in major affected organs during the infection were evaluated. Results showed that IL-27 concentration was significantly elevated throughout the infection but no positive correlation with the parasitaemia development observed. Augmentation of IL-27 significantly elevated the release of anti-inflammatory cytokine, IL-10 whereas antagonising and neutralising IL-27 produced the opposite. A significant elevation of pro-inflammatory cytokines (IFN-γ and IL-6) was also observed, both during augmentation and inhibition of IL-27. Thus, it is suggested that IL-27 exerts an anti-inflammatory activity in the Th1 type response by signalling the production of IL-10 during malaria. Histopathological examination showed sequestration of PRBC in the microvasculature of major organs in malarial mice. Other significant histopathological changes include hyperplasia and hypertrophy of the Kupffer cells in the liver, hyaline membrane formation in lung tissue, enlargement of the white and red pulp followed by the disappearance of germinal centre of the spleen, and tubular vacuolation of the kidney tissues. In conclusion, it is suggested that IL-27 may possibly acts as an anti-inflammatory cytokine during the infection. Modulation of its release produced a positive impact on inflammatory cytokine production during the infection, suggesting its potential in malaria immunotherapy, in which the host may benefit from its inhibition.

Plasmodium berghei ANKA Infection in ICR Mice as a Model of Cerebral Malaria

BACKGROUND

Animal models with various combination of host-parasite have long been employed to study malaria pathogenesis. Here, we describe the combination of Plasmodium berghei ANKA infection in inbred ICR mice as a model of cerebral malaria (CM).

METHODS

Infection in mice was initiated by intraperitoneal injection of 2 x 10(7) (0.2ml) parasitized red blood cells (PRBCs).

RESULTS

This model can produce a severe degree of infection presented by the high degree of parasitaemia followed by death 6-7 days post infection. Severe anemia, splenomegaly, hepatomegaly and discolourations of major organs were observed. Histopathological findings revealed several important features mimicking human CM including, microvascular sequestration of PRBCs in major organs, particularly in the brain, hypertrophy and hyperplasia of the kupffer cells in the liver, pulmonary edema and hyaline membrane formation in the lungs and haemorrhages in the kidney's medulla and cortex. Proinflammatory cytokines TNFα, IFNγ, IL-1, IL-6 and IL-18, and anti-inflammatory cytokine IL-10 were all found to be elevated in the plasma of infected mice.

CONCLUSION

This model can reproduce many of the important features of CM and therefore can be used as a tool to advance our understanding of the disease pathogenesis.