Lower Urinary Tract Inflammation and Infection: Key Microbiological and Immunological Aspects.

The urinary system, primarily responsible for the filtration of blood and waste, is affected by several infectious and inflammatory conditions. Focusing on the lower tract, this review outlines the physiological and immune landscape of the urethra and bladder, addressing key immunological and microbiological aspects of important infectious/inflammatory conditions. The conditions addressed include urethritis, interstitial cystitis/bladder pain syndrome, urinary tract infections, and urosepsis. Key aspects of each condition are addressed, including epidemiology, pathophysiology, and clinical considerations. Finally, therapeutic options are outlined, highlighting gaps in the knowledge and novel therapeutic approaches.

The immune response to systemically administered endotoxin in the murine intestinal microcirculation under pentobarbital versus isoflurane anesthesia.

BACKGROUND: Pentobarbital and isoflurane are commonly used veterinary anesthetics. Due to the dangers of overdose by repeat-bolus regimen of pentobarbital, isoflurane has been recommended. However, literature suggests isoflurane-induced inhibition of cytokine and adhesion molecule release, impacting leukocyte adhesion. OBJECTIVE: This study aims to characterize the impacts of pentobarbital versus isoflurane on leukocyte interactions within the intestinal microcirculation with and without endotoxin challenge. METHODS: Female BALB/c mice were subjected to pentobarbital or isoflurane (N = 20) and challenged with endotoxin or saline by intraperitoneal injection. The mice were kept under anesthesia for 2 hours. Fluorochromes, rhodamine-6 G and fluorescein isothiocyanate, were injected intravenously. To visualize leukocyte adhesion within the intestinal microcirculation, laparotomy and intravital microscopy was performed. Leukocyte rolling and adhesion was quantified offline in a blinded fashion. RESULTS: Within collecting venules, leukocyte rolling and adhesion showed no significant differences between pentobarbital and isoflurane anesthesia under basal conditions. Endotoxin challenge caused a similar response in both anesthetic groups. Within postcapillary venules, no statistical differences between the two anesthetics were found for adhering leukocytes under basal conditions or following endotoxin challenge either. However, leukocyte rolling after LPS-challenge was significantly decreased in postcapillary venules during isoflurane anesthesia compared to pentobarbital anesthesia. CONCLUSIONS: Isoflurane anesthesia showed only minor differences in the immune response to endotoxin within the intestinal microcirculation compared to pentobarbital anesthesia. Due to the superior safety profile of volatile anesthetics, immunological studies may choose isoflurane over pentobarbital as the veterinary anesthetic of choice.

Antibacterial and Analgesic Properties of Beta-Caryophyllene in a Murine Urinary Tract Infection Model.

Beta-caryophyllene has demonstrated anti-inflammatory effects in a variety of conditions, including interstitial cystitis. These effects are mediated primarily via the activation of the cannabinoid type 2 receptor. Additional antibacterial properties have recently been suggested, leading to our investigation of the effects of beta-caryophyllene in a murine model of urinary tract infection (UTI). Female BALB/c mice were intravesically inoculated with uropathogenic Escherichia coli CFT073. The mice received either beta-caryophyllene, antibiotic treatment using fosfomycin, or combination therapy. After 6, 24, or 72 h, the mice were evaluated for bacterial burden in the bladder and changes in pain and behavioral responses using von Frey esthesiometry. In the 24 h model, the anti-inflammatory effects of beta-caryophyllene were also assessed using intravital microscopy. The mice established a robust UTI by 24 h. Altered behavioral responses persisted 72 h post infection. Treatment with beta-caryophyllene resulted in a significant reduction in the bacterial burden in urine and bladder tissues 24 h post UTI induction and significant improvements in behavioral responses and intravital microscopy parameters, representing reduced inflammation in the bladder. This study demonstrates the utility of beta-caryophyllene as a new adjunct therapy for the management of UTI.

Iron Chelation in Local Infection.

Iron is an essential element in multiple biochemical pathways in humans and pathogens. As part of the innate immune response in local infection, iron availability is restricted locally in order to reduce overproduction of reactive oxygen species by the host and to attenuate bacterial growth. This physiological regulation represents the rationale for the therapeutic use of iron chelators to support induced iron deprivation and to treat infections. In this review paper we discuss the importance of iron regulation through examples of local infection and the potential of iron chelation in treating infection.

Imaging of the Intestinal Microcirculation during Acute and Chronic Inflammation.

Because of its unique microvascular anatomy, the intestine is particularly vulnerable to microcirculatory disturbances. During inflammation, pathological changes in blood flow, vessel integrity and capillary density result in impaired tissue oxygenation. In severe cases, these changes can progress to multiorgan failure and possibly death. Microcirculation may be evaluated in superficial tissues in patients using video microscopy devices, but these techniques do not allow the assessment of intestinal microcirculation. The gold standard for the experimental evaluation of intestinal microcirculation is intravital microscopy, a technique that allows for the in vivo examination of many pathophysiological processes including leukocyte-endothelial interactions and capillary blood flow. This review provides an overview of changes in the intestinal microcirculation in various acute and chronic inflammatory conditions. Acute conditions discussed include local infections, severe acute pancreatitis, necrotizing enterocolitis and sepsis. Inflammatory bowel disease and irritable bowel syndrome are included as examples of chronic conditions of the intestine.

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.

Role of reactive oxygen species and iron in host defense against infection.

Reactive oxygen species (ROS) and iron play important roles in the innate immune response. ROS are released by immune cells and are highly reactive and indiscriminately destructive in response to pathogens. In addition, ROS act as signaling molecules and play a role in apoptosis, therefore excessive ROS production can damage host molecules, leading to more harm than benefit for the host. Iron acts as a catalyst for the formation of ROS, therefore, manipulation of iron levels is a way in controlling ROS production. Iron metabolism and ROS production may affect many disease processes and must be tightly regulated for the host to generate an appropriate response. Current researches examine the roles of iron and ROS in various conditions, including neurodegeneration, inflammation, infection and cancer. Therapies directed at regulating ROS production through regulating iron levels are a major focus in these fields today.

Inflammatory Response to Different Toxins in Experimental Sepsis Models.

Sepsis is defined as life-threatening organ dysfunction caused by the dysregulated host response to infection. Despite serious mortality and morbidity, no sepsis-specific drugs exist. Endotoxemia is often used to model the hyperinflammation associated with early sepsis. This model classically uses lipopolysaccharide (LPS) from Gram-negative pathogens to activate the immune system, leading to hyperinflammation, microcirculatory disturbances and death. Other toxins may also be used to activate the immune system including Gram-positive peptidoglycan (PG) and lipoteichoic acid (LTA). In addition to these standard toxins, other bacterial components can induce inflammation. These molecules activate different signaling pathways and produce different physiological responses which can be taken advantage of for sepsis modeling. Endotoxemia modeling can provide information on pathways to inflammation in sepsis and contribute to preclinical drug development.

Selective sensitivity of the gut microbiome to iron chelators in polybacterial abdominal sepsis.

Iron chelation has been proposed as a potential therapy for polybacterial abdominal sepsis. Treatment with iron chelation is known to be able to attenuate bacterial growth. It is hypothesized that the different types of bacteria will exhibit variations in their sensitivity to iron chelation based on differences in their iron metabolism. Bacteria with weaker iron access systems might have their growth reduced initially, but stronger species may also be suppressed. Gram-positive and Gram-negative bacteria are known to possess different iron acquisition systems, which may affect their response to iron chelation. Bacteria which can produce siderophores are at a particular advantage for iron acquisition. Novel iron chelators, which do not act as xenosiderophores, may be effective in depriving these bacteria of iron. This has implications for the treatment of polybacterial sepsis, which might be enhanced if the sensitivity to iron chelation of the primary causative agents is known.