Further evidence of bradykinin involvement in septic shock: reduction of kinin production in vivo and improved survival in rats by use of polymer tailored SBTI with longer t1/2

The role of contact system in septic shock: the next target? An overview of the current evidence

BACKGROUND

Septic shock remains challenging to intensive care units worldwide, despite recent documented improvement in mortality over the years. Multiple new therapies have been attempted without success in large clinical trials. Evidence concerning the role of the contact system and bradykinin on septic shock physiological manifestations is shown by this article.

OBJECTIVES

The objective of the study is to review the current evidence linking contact system activation and septic shock, as well as efficacy of available therapies targeting this pathophysiological pathway and to evaluate the potential of further researching the matter.

RESULTS

Multiple animal studies are already available and suggestive of a meaningful role of contact system activation on septic shock. However, human trials are still scarce, and the ones available are not enough to establish such a strong connection. Furthermore, attempted therapies have been successful across multiple species, but not as much in humans. Therefore, contact system and septic shock relationship remains plentiful in questions to be answered in the coming years or decades.

CONCLUSIONS

Whether the contact system is not as relevant in humans as it is in animals or there is only lack of evidence remains to be explained. The subject is an attractive open field for further research aiming to aid in tackling such a burdensome condition.

Hypotension Following Treatment with Aerosolized Colistin in a Patient with Multidrug-Resistant Pseudomonas aeruginosa

Objective:

To report a case of a man who developed temporary hypotension after aerosolized colistin administration.

Case Summary:

A 62-year-old Arab male was admitted to the intensive care unit for respiratory failure and septic shock. Simultaneous therapy using intravenous and aerosolized colistin was initiated for the management of multidrug-resistant Pseudomonas aeruginosa. A significant but transient drop in blood pressure occurred when aerosolized colistin was introduced. However, when it was stopped, but intravenous administration was continued, no hypotension was observed. Moreover, the combined use of aerosolized amikacin with intravenous colistin did not significantly affect blood pressure.

Discussion:

It is widely accepted that aerosolization allows safe administration of colistin in the absence of significant systemic adverse effects. However, in our patient, hypotension was observed with aerosolized colistin, but not with the systemic formulation. The lack of adverse effects with administration of aerosolized amikacin in this patient demonstrates the safety of the aerosolization technique. Use of the Naranjo scale indicated a probable relationship between hypotension and aerosolized colistin administration.

Conclusions:

This case suggests that hypotension may be induced with administration of aerosolized colistin. Although this effect is rare, clinicians should be aware that hypotension may develop in critically ill patients following aerosolized colistin treatment.

The enhanced permeability retention effect: a new paradigm for drug targeting in infection

Multidrug-resistant, Gram-negative infection is a major global determinant of morbidity, mortality and cost of care. The advent of nanomedicine has enabled tailored engineering of macromolecular constructs, permitting increasingly selective targeting, alteration of volume of distribution and activity/toxicity. Macromolecules tend to passively and preferentially accumulate at sites of enhanced vascular permeability and are then retained. This enhanced permeability and retention (EPR) effect, whilst recognized as a major breakthrough in anti-tumoral targeting, has not yet been fully exploited in infection. Shared pathophysiological pathways in both cancer and infection are evident and a number of novel nanomedicines have shown promise in selective, passive, size-mediated targeting to infection. This review describes the similarities and parallels in pathophysiological pathways at molecular, cellular and circulatory levels between inflammation/infection and cancer therapy, where use of this principle has been established.

Effective antiprotease-antibiotic treatment of experimental anthrax

Background

Inhalation anthrax is characterized by a systemic spread of the challenge agent, Bacillus anthracis. It causes severe damage, including multiple hemorrhagic lesions, to host tissues and organs. It is widely believed that anthrax lethal toxin secreted by proliferating bacteria is a major cause of death, however, the pathology of intoxication in experimental animals is drastically different from that found during the infectious process. In order to close a gap between our understanding of anthrax molecular pathology and the most prominent clinical features of the infectious process we undertook bioinformatic and experimental analyses of potential proteolytic virulence factors of B. anthracis distinct from lethal toxin.

Methods

Secreted proteins (other than lethal and edema toxins) produced by B. anthracis were tested for tissue-damaging activity and toxicity in mice. Chemical protease inhibitors and rabbit immune sera raised against B. anthracis proteases were used to treat mice challenged with B. anthracis (Sterne) spores.

Results

B. anthracis strain delta Ames (pXO1^-, pXO2^-) producing no lethal and edema toxins secrets a number of metalloprotease virulence factors upon cultivation under aerobic conditions, including those with hemorrhagic, caseinolytic and collagenolytic activities, belonging to M4 and M9 thermolysin and bacterial collagenase families, respectively.

These factors are directly toxic to DBA/2 mice upon intratracheal administration at 0.5 mg/kg and higher doses. Chemical protease inhibitors (phosphoramidon and 1, 10-phenanthroline), as well as immune sera against M4 and M9 proteases of B. anthracis, were used to treat mice challenged with B. anthracis (Sterne) spores. These substances demonstrate a substantial protective efficacy in combination with ciprofloxacin therapy initiated as late as 48 h post spore challenge, compared to the antibiotic alone.

Conclusion

Secreted proteolytic enzymes are important pathogenic factors of B. anthrasis, which can be considered as effective therapeutic targets in the development of anthrax treatment and prophylactic approaches complementing anti-lethal toxin therapy.

Kinin-mediated anaphylactoid reaction implicated in acute intra-operative pulseless electrical activity

A 65-year-old patient undergoing total hip replacement under general anaesthesia suffered acute pulseless electrical activity with a fatal outcome. A kinin-mediated analphylactoid reaction following administration of a polygeline plasma expander (Haemaccel) was implicated by in vitro testing. This case report illustrates the diagnostic difficulties posed by non-histaminoid anaphylactoid reactions and the resistance to epinephrine of kinin-mediated hypotension.

Bradykinin antagonists: present progress and future prospects

Bradykinin (BK) antagonist peptides have been powerful tools for delineating roles of kinins in both normal and pathological physiology and offer promise of drug development for a variety of inflammatory conditions and cancers. At the present time, potent peptide antagonists are available that are either specific for BK B1 or B2 receptors, or are effective on both receptor classes. Non-peptide BK B2 antagonists are now being announced and are under investigation in several companies. The best peptide B1-B2 peptide antagonist is stable against all kininases, is orally available, and has a very long lifetime in vivo. Certain dimers of this antagonist, as well as several smaller molecules, are active against several cancers, both in vitro and in vivo.

Kallikrein-kinin in infection and cancer

This review article describes the mechanism of enhancement of vascular permeability in infectious disease and cancer. This phenomenon is primarily mediated by bradykinin, nitric oxide and other unique vascular mediators. They are highly intermingled with each other in these disease states. Furthermore, these mediators are elicited in various in vivo settings most frequently induced by bacterial proteases, and indirect or direct activation of kallikrein-kinin cascade at one or more steps. The key steps involve bacterial proteases or cellular components including lipopolysaccharides. Thus, the use of appropriate protease inhibitors or antagonists, or scavengers in the case of nitric oxide, superoxide or peroxynitrite, are anticipated to attenuate the clinical manifestation induced by such mediators. It also explained that fluid accumulation in ascitic or pleural compartments in the case of carcinomatosis in terminal cancer patients can be largely attributed to bradykinin or related mechanism. Systemic bacterial dissemination is also facilitated by bradykinin, or suppressed by kinin antagonists as well as by the inhibition of kinin production, respectively. Thus, control of the level of such vascular mediators appears important both in infectious disease and in cancer. alpha1-Protease inhibitor, which inhibits neutrophil elastase, is inactivated by oxidative metabolites such as superoxide and peroxynitrite, and this effect activates matrix metalloproteinases. This indicates that oxidative stress activates proteolytic potential, and thus accelerates the degenerative process upon infection.