Chemically Modified Tetracycline Prevents the Development of Septic Shock and Acute Respiratory Distress Syndrome in a Clinically Applicable Porcine Model

Abstract

Sepsis causes more than with 215,000 deaths per year in the United States alone. Death can be caused by multiple system organ failure, with the lung, in the form of the acute respiratory distress syndrome (ARDS), often being the first organ to fail. We developed a chronic porcine model of septic shock and ARDS and hypothesized that blocking the proteases neutrophil elastase (NE) and matrix metalloproteinases (MMP-2 and MMP-9) with the modified tetracycline, COL-3, would significantly improve morbidity in this model. Pigs were anesthetized and instrumented for hemodynamic monitoring and were then randomized to one of three groups: control (n = 3), laparotomy only; superior mesenteric artery occlusion (SMA) + fecal blood clot (FC; n = 7), with intraperitoneal placement of a FC; and SMA + FC + COL (n = 5), ingestion of COL-3 12 h before injury. Animals emerged from anesthesia and were monitored and treated with fluids and antibiotics in an animal intensive care unit continuously for 48 h. Serum and bronchoalveolar lavage fluid (BALF) were sampled and bacterial cultures, MMP-2, MMP-9, NE, and multiple cytokine concentrations were measured. Pigs were reanesthetized and placed on a ventilator when significant lung impairment occurred (PaO2/FiO2 < 250). At necropsy, lung water and histology were assessed. All animals in the SMA + FC group developed septic shock evidenced by a significant fall in arterial blood pressure that was not responsive to fluids. Lung injury typical of ARDS (i.e., a fall in lung compliance and PaO2/FiO2 ratio and a significant increase in lung water) developed in this group. Additionally, there was a significant increase in plasma IL-1 and IL-6 and in BALF IL-6, IL-8, IL-10, NE, and protein concentration in the SMA + FC group. COL-3 treatment prevented septic shock and ARDS and significantly decreased cytokine levels in plasma and BALF. COL-3 treatment also significantly reduced NE activity (P < 0.05) and reduced MMP-2 and MMP-9 activity in BALF by 64% and 34%, respectively, compared with the SMA + FC group. We conclude that prophylactic COL-3 prevented the development of ARDS and unexpectedly also prevented septic shock in a chronic insidious onset animal model of sepsis-induced ARDS. The mechanism of this protection is unclear, as COL-3 inhibited numerous inflammatory mediators. Nevertheless, COL-3 significantly reduced the morbidity in a clinically applicable animal model, demonstrating the possibility that COL-3 may be useful in reducing the morbidity associated with sepsis and ischemia/reperfusion injury in patients.

Lack of matrix metalloproteinase-9 worsens ventilator-induced lung injury

“…coworkers (42). The most important source of MMP-9 is neutrophils (36), which are recruited from the circulation during VILI, but macrophages can also release this metalloprotease.…”

“…Currently, MMPs are viewed as modulators of cell-cell and cell-matrix interactions (37). Among them, MMP-9 (gelatinase B) has gained some attention in different models of lung injury (39,42) including VILI (14,25). The levels of MMP-9 have also been found to be raised in patients with acute lung injury (13,40,50).…”

“…On the basis of these findings, it has been suggested that MMP-9 inhibition could be useful in models of sepsis (42), acute lung injury (8), and VILI (14,25) by decreasing the inflammatory response and tissue damage. However, nonselective inhibitors can modify the activity of other enzymes, precluding any firm conclusion on the specific role of MMP-9.…”

Matrix Metalloproteinase-2 Proteolysis of Calponin-1 Contributes to Vascular Hypocontractility in Endotoxemic Rats

“…10 -12,24 A significant involvement of MMPs and the beneficial effects of their inhibition have been shown in experimental models of sepsis [17][18][19][20][21][22] although proteolytic targets have not yet been identified. MMP-2 plays an important role in LPS-induced aortic hypocontractility in vivo and in vitro as its effects were completely prevented with either doxycycline or GM6001.…”

“…[17][18][19][20][21][22][23] MMP-2 plays an important role in LPS-induced vascular hypocontractility in rats. In vivo treatment with the MMP inhibitor doxycycline attenuated LPS-induced increase in vascular MMP-2 activity and protected against the loss of vascular contractile tone.…”