Effect of fusidic acid on interleukin-1 (IL-1)- and IL-6-induced pancreatic beta-cell functions in rats

The microbiome and rodent models of immune mediated diseases

Over the last six decades production of laboratory rodents have been refined with the aim of eliminating all pathogens, which could influence research results. This has, however, also created rodents with little diversity in their microbiota. Until 10 years ago the impact of the microbiota on the outcome of rodent studies was ignored, but today it is clear that the phenotype of rodent models differs essentially in relation to the environment of origin, i.e. different breeders or different rooms. In this review, we outline the mechanisms behind gut bacterial impact on rodent models of immune mediated diseases, and how differences in environment of origin leads to phenotypic model differences within research areas such as infectious diseases and vaccine development, the metabolic syndrome, gut immunity and inflammation, autoimmunity and allergy. Finally, we sum up some tools to handle this impact to increase reproducibility and translatability of rodent models.

Effect of Fusidic Acid on Pancreatic Islet Allograft Rejection

We examined in fully mismatched rats, the survival of pancreatic islet allografts in recipients treated with either fusidic acid (FA), an antistaphyllococcal antibiotic that has been shown to possess an immunosuppressive effect in vitro and in vivo, or cyclosporin-A (CsA). Islets were isolated by collagenase digestion, separated from acinar tissue by handpicking under a dissecting microscope and transplanted into the liver by portal vein injection of streptozotocin(STZ)-induced diabetic rats. The results indicated that while a temporary immunosuppression with CsA achieved an indefinite islet allograft survival, FA administered to recipients daily was not able to prevent islet allograft rejection across a major histocompatibility barrier. We conclude that despite the fact that fusidic acid has been claimed to act as an immunosuppressant drug in vitro with effects similar to those of CsA, unlike CsA, FA given either orally or by s.c. injection was not effective to prolong islet allograft survival in vivo. Copyright © 1997 Elsevier Science Inc.

Dietary gluten reduces the number of intestinal regulatory T cells in mice

It is well established that gluten-free diet reduces the incidence of type 1 diabetes mellitus (T1D) in non-obese diabetic (NOD) mice, though the mechanism is not known. However, regulatory T cells (Treg) are likely to play an important role. Also, it is known that dietary gluten induces an intestinal increase in the bacterium Lactococcus garvieae, but the importance of this phenomenon for T1D development is doubtful. Our hypothesis is that gluten is responsible for mediating its effect on T1D through the influence on Treg development independent of gluten-induced Lactococci. Four groups of female NOD and BALB/c mice of 3 week old were fed either a gluten-free diet or a standard diet. Lactococcus garvieae or saline water was administered per oral to one of each dietary group. Spleen and Peyer's patches were sampled from BALB/c mice for flow cytometric monitoring of IL-10 and Treg. NOD mice were diagnosed diabetic with blood glucose level >12 mmol/l. Dietary gluten significantly decreased the occurrence of Tregs by 10-15% (P < 0.05) in mice compared with those fed a standard diet. These results and the diabetes incidence were independent of the gluten-induced bacterial factor Lactococci. The prevalence of Treg was 5- to 10-fold more abundant in the Peyer's patches than in the spleen (P < 0.001). In conclusion, dietary gluten has a significant negative quantitative impact on the generation of Treg in mice, independent of gluten-induced Lactococcus garvieae, and Treg are far more abundant in Peyer's patches than in the spleen.

Antibiotic treatment partially protects against type 1 diabetes in the Bio-Breeding diabetes-prone rat. Is the gut flora involved in the development of type 1 diabetes?

AIMS/HYPOTHESIS

Accumulating data suggest that the gut immune system plays a role in the development of type 1 diabetes. The intestinal flora is essential for the development of the (gut) immune system and the establishment of tolerance. It has been reported that oral administration of food and bacterial antigens early in life suppresses later development of diabetes in the Bio-Breeding diabetes-prone (BB-DP) rat. This study was designed to investigate the possible relationship between the development of diabetes and the composition of intestinal flora.

MATERIALS AND METHODS

The intestinal flora of BB-DP rats, a rat model for type 1 diabetes, was characterised long before the clinical onset of diabetes by fluorescent in situ hybridisation. In a separate experiment, BB-DP rats were treated with antibiotics and the effect on diabetes incidence and level of insulitis was analysed.

RESULTS

We observed a difference in bacterial composition between rats that eventually did and those that did not develop diabetes. This difference was detectable long before clinical onset of the disease. Rats that did not develop diabetes at a later age displayed a lower amount of Bacteroides sp. Modulation of the intestinal flora through antibiotic treatment decreased the incidence and delayed the onset of diabetes. A combination of antibiotic treatment and a protective hydrolysed casein diet completely prevented diabetes in the BB-DP rat.

CONCLUSIONS/INTERPRETATION

Our data suggest that the intestinal flora is involved in the development of type 1 diabetes. Factors influencing composition of the intestinal flora could be a target for therapeutic intervention.

Antidiabetogenic effect of fusidic acid in diabetes prone BB rats: a sex-dependent organ accumulation of the drug is seen

Fusidic acid and its sodium salt (fusidin) are widely used antistaphylococcal drugs which possesses immunomodulatory properties. This prompted us to investigate whether high concentrations of fusidin could lower the diabetes incidence in diabetes-prone BB (BioBreeding) rats. As fusidin has previously been claimed to be poorly absorbed in rats after oral administration we wanted to measure the activity of the drug in various organs. Three groups of BB rats were used: 63 rats received fusidin dissolved in drinking water; 65 rats received chow containing fusidin; and 72 rats served as controls. The content of fusidin in the organs were examined microbiologically. The incidence of diabetes was significantly lower in the two fusidin-treated groups compared to the control group. The incidence was lower for male than for female rats in both experimental groups while no gender difference was seen in the control group. The female rats had a substantially higher content of fusidin in their organs than the males regardless of the administration way and regardless of diabetes outbreak or not. Interestingly, the fusidin treated non-diabetic rats displayed a lower random blood glucose level than the controls. In conclusion, fusidin is well absorbed after oral administration and it significantly reduces the diabetes incidence in BB rats. Fusidin accumulates substantially more in female rats which may be due to the steroid structure of fusidin. Whether the same phenomenon takes place in human beings is not known.

Sodium fusidate ameliorates the course of diabetes induced in mice by multiple low doses of streptozotocin

We studied the effects of the immunosuppressant sodium fusidate (fusidin) on murine immunoinflammatory diabetes mellitus (DM) induced by multiple low doses of streptozotocin (SZ). Fusidin was given by gavage to three strains of mice (C57KsJ, C57BL/6, CD1) at doses 10 or 100 mg/kg body weight every other day. The drug was administered as an early or late prophylactic regime starting either 1 day prior to the first or after the fifth and last injection of SZ. In both situations the largest dose of fusidin successfully reduced the clinical, chemical and histological signs of DM, the treated mice having significantly lower glycaemic values and milder (often absent) insulitis compared with sham-treated animals or controls given SZ alone. The antidiabetogenic effect was long-lasting as it was maintained up to 1 month after cessation of therapy. In contrast, fusidin prophylaxis failed to prevent development of hyperglycaemia acutely induced by one single and high (160 mg/kg) dose of SZ, which is a model of DM primarily due to the toxic action of SZ on the beta cells and does not involve immunopathogenetic mechanisms. On day 14 after SZ, fusidin markedly altered the circulating cytokine profile induced in vivo by ConA, reducing the levels of IFN-gamma, IL-2 and TNF-alpha and augmenting the level of IL-6. However, only the inhibitory effect of the drug on the synthesis/release of IFN-gamma seemed to be causally related to its capacity to counteract the SZ-induced DM. In fact, the disease was prevented by a neutralizing monoclonal antibody (mAb) against IFN-gamma, but not by anti-IL-2 receptor mAb, a soluble form of TNF-receptor type 1 or recombinant human IL-6. The prevention of disease by fusidin was also partly reversed by exogenously administered recombinant mouse IFN-gamma. The data provide further in-vivo evidence for the anti-diabetogenic and immunomodulatory properties of fusidin and indicate that this drug could have a role in prevention and treatment of human type 1 DM.

Amelioration of experimental allergic neuritis by sodium fusidate (fusidin): suppression of IFN-gamma and TNF-alpha and enhancement of IL-10

The immunomodulating antibiotic drug fusidic acid and its sodium salt sodium fusidate (fusidin) ameliorate several organ-specific immunoinflammatory diseases. Because preliminary observations suggest that fusidin may also exert a beneficial effect in Guillain-Barré syndrome (GBS), here we have studied the effects of fusidin on actively induced experimental autoimmune neuritis (EAN) in rats, a known animal model for GBS. Both prophylactic and therapeutic treatment with fusidin (4 mg/rat day ip) markedly ameliorated the clinical course of the disease compared to vehicle-treated animals. The beneficial effects were associated with profound modifications of the capacity of these rats to produce and release pro- and anti-inflammatory cytokines such as IFN-gamma, TNF-alpha and IL-10, which are important in regulating the development of EAN.

Fusidic acid non-antibacterial activity

In 1978 the first report was published indicating that fusidic acid had an immunomodulatory effect. This study describing an in vitro effect on white cells was followed by an in vivo study showing improved survival in heart transplanted mice. In 1990 these immunomodulatory effects were shown to be related to suppression of cytokine production in animal models of septic shock and insulin dependent diabetes. Disease modulation has been investigated in a number of immunologically mediated diseases, HIV infection, Behcet's disease, Crohn's disease, uveitis and scleroderma. However whether fusidic acid has any useful function as an immunomodulating agent has yet to be fully explored.

Sodium fusidate and the cytokine response in an experimental model of acute pancreatitis

BACKGROUND

New therapies designed to downregulate the aberrant immune response associated with severe acute necrotizing pancreatitis (ANP) are being increasingly investigated in different experimental models of ANP. The aim of this study was to test the potential effects of sodium fusidate on the course of severe ANP in rabbits.

METHODS

ANP was induced in 20 rabbits by retrograde injection of 5 per cent chenodeoxycholic acid into the pancreatic duct followed by duct ligation. The rabbits were allocated to pretreatment with intravenous physiological saline or sodium fusidate 80 mg/kg 30 min before the induction of ANP. Levels of serum amylase, lipase, tumour necrosis factor (TNF) alpha, interleukin (IL) 8, glucose and calcium, and leucocyte count were measured every 3 h for a total of 12 h. At the end of the experiment, ascitic fluid was collected and the pancreatic, lung and kidney tissues were obtained for histological examination.

RESULTS

Pretreatment with sodium fusidate reduced the mortality rate from six of ten to three of ten (P < 005) and reduced the output of ascitic fluid from 5 2 to 2.0 ml/h (P < 0001). Serum levels of TNF-alpha and IL-8 were reduced significantly in the treated group from 5 min up to 9 h after induction of ANP. The leucopenia observed after 3 h in the untreated group was not significantly improved in the group treated with sodium fusidate (P = 0.055). By contrast, both treated and untreated rabbits had similar biochemical changes including levels of amylase, lipase, glucose and calcium as well as similar histological changes in the pancreas and lungs.

CONCLUSION

Pretreatment with sodium fusidate resulted in a considerable reduction in mortality rate and ascitic fluid output in rabbits with bile-induced ANP, probably by lowering the TNF-alpha and IL-8 blood levels. However, pretreatment with sodium fusidate did not alter the local or systemic manifestations of ANP. Thus, cytokines other than TNF-alpha and IL-8 are likely to mediate the local and systemic symptoms of ANP.

Fusidic acid and insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) is a major cause of morbidity and mortality from long-standing complications. The autoimmune nature of IDDM has encouraged use of immunosuppressive and antiinflammatory strategies to better preserve residual pancreatic beta-cell function at the time of diagnosis. Fusidic acid and its sodium salt, fusidin, is a relatively atoxic antibiotic used mainly in the treatment of staphylococcal infections. Recently, fusidin has been demonstrated to possess immunosuppressive functions in vitro and in vivo, and the drug has shown promise in preventing the disease in animal models of IDDM and in a preliminary trial in IDDM patients.

Immunological influences in attention-deficit disorder and schizophrenia; is there a link between these two conditions?

This paper aims to explore the influence of the immune system on the pathobiochemistry of movement disorders (Tourette syndrome, obsessive compulsive disorders and attention-deficit disorder, with and without hyperactivity) and schizophrenia. In children, a temporal relationship has been observed between contraction of a group A beta-hemolytic streptococcal infection and subsequent presentation with one of the movement disorders. Pathology investigations reveal that elevated antineuronal antibodies are associated with movement disorders. Similarly, elevations in interleukin-1 beta and interleukin-6 have been reported in schizophrenia. It is now known that the immune system can be activated by conditions other than a viral or bacterial infection, such as: neurological insult, neurotoxicity--endogenous and environmental, neurotransmitter and cholesterol dysregulation. These latter avenues of immune system activation will be explored with respect to schizophrenia.

Interleukin-1 beta: a common cause of Alzheimer's disease and diabetes mellitus

Alzheimer disease is characterized by the presence of beta-amyloid protein deposits, neurofibrillary tangles and cholinergic dysfunction throughout the hippocampal region. In addition, the hippocampus, hypothalamus and olfactory bulb--the three areas where the insulin receptors are most dense--are also subject to neurodegeneration. The exact cause of the beta-amyloid deposits and NFTs is unknown. However, it is our intention to explicate the various pathogenic pathways through which Alzheimer disease arises. Fundamentally, the structural and metabolic damage found in Alzheimer disease is due to sustained elevation of interleukin-1 beta, a feature which is also found in insulin-dependent diabetes mellitus. Similarly, the beta-AP deposits found in the Alzheimer brain share the same molecular structure as the amylin deposits found in the pancreatic beta-cells in non-insulin-dependent diabetes mellitus (NIDDM), and are equally neurotoxic. These, and other pathophysiological parallels, afford some insight into the probably cause of Alzheimer disease and, as such, forms the basis of the causal hypothesis advanced in this paper.

Anti-tumor necrosis factor properties of non-peptide drugs in acute-phase responses

Dexamethasone (sodium phosphate), pentoxifylline, fusidic acid (sodium salt), pentamidine (isethionate) and R-phenylisopropyladenosine (R-PIA) were tested for their anti-tumor necrosis factor (TNF) activities in an endotoxin-induced shock rat model. All the drugs reduced serum TNF concentrations in a dose-dependent manner, whereas their effects on serum interleukin-6 levels differed. Doses that reduced TNF levels by 50% were 0.012 mg/kg for dexamethasone, 0.06 mg/kg for R-PIA, 0.24 mg/kg for pentamidine, 6.5 mg/kg for fusidic acid and 15 mg/kg for pentoxifylline. Administration of the drugs to rats before intraplantar injection of carrageenan reduced paw edema by 50-70%. Injection of a monoclonal anti-TNF antibody reproduced the inhibitory effect. Moreover, the time course of tissue-associated TNF following carrageenan injection was compatible with mediation of edema by TNF. Results obtained for this acute, non-immunological inflammatory reaction strongly suggest that the model is TNF-dependent. Our results reinforce the idea that TNF is a crucial target in the therapeutics of inflammatory reactions. These drugs, which are able to cross cell barriers, might have clinical applications in localized and/or chronic diseases in which TNF is involved.

Fusidic acid suppresses nitric oxide toxicity in pancreatic islet cells

Earlier preclinical and clinical trials indicate that fusidic acid, a triterpenoid compound originally described as an antimicrobial drug may protect islet beta cells from destruction in type I (insulin-dependent) diabetes mellitus. Since nitric oxide appears to be an important mediator of inflammatory islet cell death we analyzed whether fusidic acid interferes with nitric oxide production or action. We report here that fusidic acid dose-dependently inhibits lysis of isolated islet cells by activated macrophages, a process mediated by nitric oxide. In the presence of 100 microM fusidic acid macrophage-mediated islet cell lysis was reduced from 52.5 to 1.7% (P < 0.001). Fusidic acid only slightly affected macrophage function and did not inhibit the release of nitric oxide. We therefore tested whether fusidic acid suppresses nitric oxide toxicity in target cells. Isolated islet cells were exposed to the nitric oxide donor nitroprusside which led to DNA strand breaks and plasma membrane lysis. DNA strand breaks were reduced from 54.6 to 34.9% (P < 0.001) in the presence of 100 microM fusidic acid and cell lysis was reduced from 60.1 to 27.5% with 100 microM (P < 0.001). In the presence of 500 microM fusidic acid DNA strand breaks and cell lysis were reduced further to 27.1 and 10.7%, respectively (P < 0.001). No protection by fusidic acid was observed when cells were exposed to oxygen radicals or the alkylating beta cell toxin streptozotocin. The suppression of nitric oxide toxicity by fusidic acid was not due to its known inhibitory action on protein biosynthesis and thus represents a hitherto unknown activity of this drug.

Morphological effects of sodium fusidate (fusidin) on pancreatic islet cells: an electron microscopic study

Fusidic acid has been shown to prevent the lymphocyte co-stimulatory activities of cytokines and seems--in preliminary trials--clinically effective as an immunoregulatory drug e.g. in insulin-dependent diabetes mellitus. A toxic effect of fusidic acid may however be suspected since a previous study showed a significant dilatation of rough endoplasmic reticulum in cultured pancreatic islet cells from normal rats. In this study we examined the ultrastructural effects of the sodium salt of fusidic acid (fusidin) on cultured rat islet cells (treatment period 3-5 days), and of islet cells from rats receiving fusidin for 6 days. Electron microscopically, fusidin treatment in vitro (3 to 30 micrograms/ml) showed a significant dilatation of the rough endoplasmic reticulum of islet cells. No dose dependent changes were found. In the in vivo model no changes were demonstrated in concentrations of fusidin up to 9.64 micrograms/ml of homogenated pancreatic tissue. It is concluded that treatment with fusidin gives no detectable ultrastructural changes in vivo.

Anti-diabetogenic effect of fusidic acid in diabetes prone BB rats

Fusidic acid and its sodium salt (fusidin) are anti-staphylococcal drugs. In vitro studies have shown that they prevent the lymphocyte co-stimulatory activities of the cytokines IL-1 and IL-6 in a manner similar to that of cyclosporin A, and prevent the inhibitory effect of IL-1 on glucose-induced insulin production. As IL-1 and IL-6 are thought to play a role in the pathogenesis of Type 1 diabetes, the aim of this study was to investigate whether fusidin could influence the disease incidence of the spontaneously diabetic BB rat model. Accordingly, a group of 50 BB rats receiving fusidin dissolved in their drinking water were compared to a control group of 55 rats over a period of 200 days. The incidence of diabetes was found to be 52% in the experimental group and 71% in the control group (P < 0.05). The degree of insulitis and the number of islets at histological examination were similar among the non-diabetic animals whereas the diabetic fusidin-treated animals showed a higher degree of islet preservation than the diabetic control rats. The results are highly indicative of an anti-diabetogenic effect of fusidin.