Doxycycline Attenuates Leptospira-Induced IL-1β by Suppressing NLRP3 Inflammasome Priming

Abstract

Doxycycline (Dox), a semisynthetic antibiotic, has been reported to exert multiple immunomodulatory effects. Treatment with Dox has a satisfactory curative effect against leptospirosis. In addition to its antibacterial action, we supposed that Dox also modulated immune response in controlling leptospira infection. Using J774A.1 mouse macrophages, the effects of Dox on protein and mRNA levels of IL-1β and TNF-α were investigated after infection with live or sonicated Leptospira interrogans serovar Lai strain Lai (56601). Specifically, the level of IL-1β but not TNF-α was sharply decreased when treated with Dox in leptospira-infected macrophages. Western blot analysis showed that Dox suppressed the activation of leptospira-induced MAPK and NF-κB signaling pathways. Using NLRP3-deficient and NLRC4-deficient mice, the data showed that the expression of leptospira-induced IL-1β was mainly dependent on the presence of NLRP3 inflammasome in macrophages. Meanwhile, Dox suppressed leptospira-induced NLRP3 inflammasome priming with the upregulation of the Na/K-ATPase Pump β1 subunit. The inhibition effect of Dox on IL-1β was also conspicuous in cells with lipopolysaccharide and ATP stimulation. These results were confirmed in vivo, as peritoneal fluids of mice and organs of hamsters expressed less IL-1β after treatment of leptospiral infection with Dox. Our results indicated that Dox also modulated immune response to attenuate leptospira-induced IL-1β by suppressing p38, JNK, p65, and NLRP3 inflammasome priming.

Recent findings related to immune responses against leptospirosis and novel strategies to prevent infection

“…Additionally, the inhibition of the sodium/potassium (Na/K) pump by glycolipoprotein, an outer membrane component, results in NLRP3 activation and processing of the pro-IL-1b protein to secreted IL-1b [41]. A recent study highlighted a novel role for doxycyclin in inhibiting the IL-1b production in mouse and hamsters cells infected with leptospires [42]. One specific effect of doxycyclin is to restore the Na/K pump expression that is inhibited by leptospires, while another role (not specific to leptospires) is to downregulate NLRP3 and IL-1b mRNAs.…”

The preventable efficacy of β-glucan against leptospirosis

“…It has been widely reported that immunosuppressive agents protect the host from Leptospira infection [7,8], whereas in previous studies, it was found that the inflammatory storm in the susceptible model after infection was delayed and more severe than in the tolerant model [9]. The innate immune system constitutes the first line of host defense, playing a crucial role in the early recognition and elimination of leptospires [10].…”

Phagocyte Escape of Leptospira: The Role of TLRs and NLRs

“…We also showed that leptospiral activation of the inflammasome was mostly limited to NLRP3 and excluded other potential inflammasomes, such as NLRC4/NAIP5, which recognize flagellin. NLRP3-dependent IL1β secretion was confirmed in a recent study showing that doxycyclin reduced IL1β secretion in J774 murine MΦ cells infected with leptospires ( 137 ). Subsequently, it was shown that leptospires also trigger the NLRP3 inflammasome in the THP1 human MΦ cell line ( 120 ).…”