Anti-Inflammatory Effects of the Iron Chelator, DIBI, in Experimental Acute Lung Injury

Iron plays a critical role in the immune response to inflammation and infection due to its role in the catalysis of reactive oxygen species (ROS) through the Haber-Weiss and Fenton reactions. However, ROS overproduction can be harmful and damage healthy cells. Therefore, iron chelation represents an innovative pharmacological approach to limit excess ROS formation and the related pro-inflammatory mediator cascades. The present study was designed to investigate the impact of the iron chelator, DIBI, in an experimental model of LPS-induced acute lung injury (ALI). DIBI was administered intraperitoneally in the early and later stages of lung inflammation as determined by histopathological evaluation. We found that lung tissues showed significant injury, as well as increased NF-κB p65 activation and significantly elevated levels of various inflammatory mediators (LIX, CXCL2, CCL5, CXCL10, IL-1𝛽, IL-6) 4 h post ALI induction by LPS. Mice treated with DIBI (80 mg/kg) in the early stages (0 to 2 h) after LPS administration demonstrated a significant reduction of the histopathological damage score, reduced levels of NF-κB p65 activation, and reduced levels of inflammatory mediators. Intravital microscopy of the pulmonary microcirculation also showed a reduced number of adhering leukocytes and improved capillary perfusion with DIBI administration. Our findings support the conclusion that the iron chelator, DIBI, has beneficial anti-inflammatory effects in experimental ALI.

Comparison of Treatment Effects of Different Iron Chelators in Experimental Models of Sepsis

Growing evidence indicates that dysregulated iron metabolism with altered and excess iron availability in some body compartments plays a significant role in the course of infection and sepsis in humans. Given that all bacterial pathogens require iron for growth, that iron withdrawal is a normal component of innate host defenses and that bacterial pathogens have acquired increasing levels of antibiotic resistance, targeting infection and sepsis through use of appropriate iron chelators has potential to provide new therapeutics. We have directly compared the effects of three Food and Drug Administration (FDA)-approved chelators (deferoxamine—DFO; deferiprone—DFP; and deferasirox—DFX), as were developed for treating hematological iron overload conditions, to DIBI, a novel purpose-designed, anti-infective and anti-inflammatory water-soluble hydroxypyridinone containing iron-selective copolymers. Two murine sepsis models, endotoxemia and polymicrobial abdominal sepsis, were utilized to help differentiate anti-inflammatory versus anti-infective activities of the chelators. Leukocyte adhesion, as measured by intravital microscopy, was observed in both models, with DIBI providing the most effective reduction and DFX the poorest. Inflammation in the abdominal sepsis model, assessed by cytokine measurements, indicated exacerbation by DFX and DFO for plasma Interleukin (IL)-6 and reductions to near-control levels for DIBI and DFP. Peritoneal infection burden was reduced 10-fold by DIBI while DFX and DFP provided no reductions. Overall, the results, together with those from other studies, revealed serious limitations for each of the three hematological chelators, i.e., as potentially repurposed for treating infection/sepsis. In contrast, DIBI provided therapeutic benefits, consistent with various in vitro and in vivo results from other studies, supporting the potential for its use in treating sepsis.

Anti-inflammatory iron chelator, DIBI, reduces leukocyte-endothelial adhesion and clinical symptoms of LPS-induced interstitial cystitis in mice

BACKGROUND

Interstitial cystitis (IC) is a prevalent and debilitating chronic inflammatory disease of the urinary bladder. Currently there are no fully effective therapeutic agents available, in part due to the still obscure pathogenesis of IC. Lipopolysaccharide (LPS) also known as endotoxin from Gram negative bacteria elicits IC in mice and has formed the basis of model systems for investigation. Excess free iron plays an important role in inflammation through generation of reactive oxygen species (ROS). The novel iron chelator DIBI has been shown to sequester excess free iron and dampen excess inflammatory responses to systemic LPS administration and also to Gram negative bacterial infections.

OBJECTIVE

The overall objective of this study was to evaluate the effects of DIBI on LPS induced IC in mice. Leukocyte activation, endothelial adhesion and functional capillary density were assessed by intravital microscopy of the bladder microcirculation following a single intravesical LPS administration with or without intravesical DIBI treatment. Clinical IC symptoms were also assessed through behavioral and pain threshold force measurements.

METHODS

Four groups of female BALB/c mice (n = 5-6/group) were randomized in this study: control group, IC group without therapy, IC group with DIBI therapy and control group with DIBI therapy. The groups were examined using intravital microscopy (IVM) of the bladder for leukocyte-endothelial interactions (adherent leukocytes, temporarily interacting leukocytes) and functional capillary density (FCD). A modified behavioral score by Boucher et al. and Von-Frey-Aesthesiometry were used to evaluate key behavioral indices related to pain and visceral pain perception.

RESULTS

LPS introduced intravesically induced an early (≤2h) inflammation of the bladder evidenced by leukocyte activation and adhesion to bladder capillary walls. Intravesical DIBI therapy of mice 30min following LPS administration and assessed after 1.5h treatment showed a significant decrease in the number of adherent leukocytes compared to IC animals without DIBI treatment. DIBI treated mice showed a significantly lowered increase in behavioral distress scores compared to IC mice without therapy. Untreated IC mice exhibited a significantly decreased threshold force value for evoked pain response and DIBI treatment improved the threshold pain response. A significant inverse correlation was found for the two pain and suffering evaluation methods results.

CONCLUSION

DIBI reduced inflammatory endothelial leukocyte adhesion and key indices related to pain and suffering over those observed in untreated IC mice. Our findings suggest a potential therapeutic role for DIBI for IC treatment.

The novel iron chelator, DIBI, attenuates inflammation and improves outcome in colon ascendens stent peritonitis-induced experimental sepsis

BACKGROUND

Sepsis is the result of a dysregulated host immune response to an infection. An ideal therapy would target both the underlying infection and the dysregulated immune response. DIBI, a novel iron-binding polymer, was specifically developed as an antimicrobial agent and has also demonstrated in vivo anti-inflammatory properties.

OBJECTIVE

This study aimed to further investigate the effects of DIBI with and without the antibiotic imipenem (IMI) in colon ascendens stent peritonitis (CASP)-induced experimental sepsis.

METHODS

Vehicle, DIBI and/or IMI were administered in C57BL/6 mice after CASP surgery. Intestinal leukocyte activation and capillary perfusion was evaluated by intravital microscopy. Moreover, bacterial load in peritoneal lavage fluid and blood, and plasma cytokine levels were assessed. In a second series of experiments, surgery to repair the colon was performed at 5 hr and these mice were followed for long-term survival over 7 days.

RESULTS

DIBI reduced leukocyte adhesion, improved capillary blood flow, and decreased key plasma cytokines levels. DIBI also improved survival of infected mice and greatly improved IMI efficacy. Survivors treated with IMI and DIBI were found to be free of systemic infection.

CONCLUSIONS

DIBI has promising potential for sepsis treatment including its use as a sole or an adjunct therapeutic with antibiotics.

Iron Chelation in Murine Models of Systemic Inflammation Induced by Gram-Positive and Gram-Negative Toxins

Iron is an essential element for various physiological processes, but its levels must remain tightly regulated to avoid cellular damage. Similarly, iron plays a dual role in systemic inflammation, such as with sepsis. Leukocytes utilize iron to produce reactive oxygen species (ROS) to kill bacteria, but pathologically increased iron-catalyzed ROS production in sepsis can lead to damage of host cells, multi-organ failure and death. Temporary reduction in bioavailable iron represents a potential therapeutic target in sepsis. This study investigates the effect of the novel iron chelator, DIBI, in murine models of systemic (hyper-)inflammation: C57BL/6 mice were challenged with toxins from Gram-positive (Staphylococcus aureus: lipoteichoic acid, peptidoglycan) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae: lipopolysaccharide). Intravital microscopy (IVM) was performed to assess immune cell activation and its impact on microvascular blood flow in vivo in the microcirculation of the gut. Plasma inflammatory mediators were measured via multiplex assay, and morphologic change in intestinal tissue was evaluated. DIBI treatment decreased leukocyte (hyper-)activation induced by Gram-positive and Gram-negative toxins. In some cases, it preserved capillary perfusion, reduced plasma inflammatory markers and attenuated tissue damage. These findings support the utility of DIBI as a novel treatment for systemic inflammation, e.g., sepsis.

Iron Chelation as Novel Treatment for Interstitial Cystitis

Interstitial cystitis (IC) is a highly prevalent debilitating disease, with its cardinal symptoms being severe pain, urinary urgency and frequency. The associated pain may eventually lead as a last resort to removal of the bladder. Though the initial trigger for IC remains largely unknown, we propose novel iron chelators as a possible new treatment for this disease. Iron is a mandatory component for the generation of reactive oxygen species (ROS). A substantial decrease in ROS production and thus inflammation can be achieved by effectively sequestering host iron, which we believe may improve outcome and quality of life in IC patients. Novel iron chelators could be used via the intravesical route to reduce or attenuate inflammation by effectively sequestering host iron, thus preventing the production of ROS via the Fenton and Haber-Weiss reactions.

Anti-inflammatory effects of a novel iron chelator, DIBI, in experimental sepsis

BACKGROUND

Iron catalyzes the generation of reactive oxygen species (ROS) as part of the innate antimicrobial defense. During sepsis, the dysregulated systemic inflammatory response to infection, iron homeostasis becomes disrupted, generating an excess of ROS causing damage to tissues. This can be potentially suppressed using iron chelators that selectively bind iron to prevent its participation in ROS-related inflammatory reactions.

OBJECTIVE

We hypothesize that administration of DIBI, a novel iron-chelator, attenuates the dysregulated systemic immune response and reduces tissue damage in experimental endotoxemia.

METHODS

Five groups of animals (n = 5-10) were included in this study: control, untreated endotoxemia, and endotoxemia animals treated with either DIBI-A, MAHMP, or DIBI-B. Intravital microscopy was performed on the intestine of anesthesized mice to observe leukocyte endothelial interactions and evaluate the intestinal microcirculation.

RESULTS

Treatment of endotoxemic mice with DIBI-B reduced the number of adhering leukocytes in submucosal collecting (V1) venules by 68%. DIBI-B, MAHMP, and DIBI-A were able to restore functional capillary density (FCD) in the intestinal muscle layer by 74%, 44%, and 11%, respectively.

CONCLUSIONS

DIBI-B reduces leukocyte recruitment and improves FCD in experimental endotoxemia, outperforming other chelators tested. These findings suggest a potential role for DIBI-B as a candidate drug for sepsis treatment.