The transcriptomic response of Streptococcus pneumoniae following exposure to cigarette smoke extract

Abstract

Exposure to cigarette smoke is a risk factor for respiratory diseases. Although most research has focused on its effects on the host, cigarette smoke can also directly affect respiratory pathogens, in some cases enhancing virulence. Streptococcus pneumoniae (the pneumococcus) is a leading cause of community-acquired pneumonia worldwide, however data on the effects of cigarette smoke on the pneumococcus are sparse. Using RNA-seq, we show that pneumococci exposed to cigarette smoke extract in a concentrated acute exposure in vitro model initiate a ‘survival’ transcriptional response including the upregulation of detoxification enzymes, efflux pumps and osmoregulator transporters, as well as the downregulation of fatty acid and D-alanyl lipoteichoic acid biosynthesis genes. Except for the downregulation of the pneumolysin gene, there were no changes in the expression of major virulence factors following exposure to cigarette smoke. Compared to unexposed pneumococci, smoke-exposed pneumococci did not exhibit any changes in viability, adherence, hydrophobicity or cell lysis susceptibility. In this study, we demonstrate that pneumococci adapt to acute noxious cigarette smoke exposure by inducing a gene expression signature that allows the bacteria to resist its harmful effects.

The effects of e-cigarette vapor exposure on the transcriptome and virulence of Streptococcus pneumoniae

“…Notably, we did not observe upregulation of genes encoding TCS11 (SP_2000/SP_2001) in CSE-TIGR4 or in EVE +NIC -TIGR4 (Table 1). These results contradict previous observations that CS exposure upregulates transcription of TCS11 genes in pneumococcal serotypes 19F and 23F indicating the strain-dependent nature of these effects [18, 19]. Both CSE-TIGR4 and EVE +NIC -TIGR4 also exhibited altered expression of genes involved in carbon uptake and metabolism (phosphotranferase systems/PTS), pneumococcal stress response (Clp proteases, hrcA /SP_0515) and transcriptional regulators ( mgrA /SP_1800, marR /SP_1863, merR /SP_1856) and (Table 2).…”

“…In contrast to its effects on biofilm formation, exposure to EVE +NIC , EVE −NIC , or CSE did not significantly alter the ability of TIGR4 to adhere to human lung epithelial cell line A549 (Fig 2B), hydrophobicity (Fig 2C), or pneumococcal sensitivity to hydrogen peroxide (Fig 2D). This is similar to the previous report by Manna et al demonstrating that 30 min CSE-exposure does not significantly alter TIGR4 hydrophobicity or adherence to A549 [19].…”

“…According to the Centers for Disease Control and Prevention, approximately 50,000 deaths in 2017 were attributed to pneumonia, making it a leading cause of infection-related deaths in the USA [23]. Exposure to cigarette smoke is a key risk factor for pneumonia because it affects the physiology and immune responses of the respiratory tract and augments the virulence of pathogens colonizing the nasopharyngeal mucosa [10–19]. In contrast, various effects of e-cigarette use on the composition and physiology of nasopharyngeal microflora are relatively unknown.…”

“…Comparison of transcriptome profiles of the treatments with control TS-TIGR4 informed our understanding of the effects of EV ± nicotine and CS on the expression of genes involved in pneumococcal survival, stress response, and virulence. The transcriptome profiling of CSE-TIGR4 served as a control, based on the results published by Manna et al [19]. Importantly, we also compared the virulence of EVE +NIC -TIGR4, EVE −NIC -TIGR4, CSE-TIGR4, and TS-TIGR4 by monitoring disease progression in a mouse model of acute pneumonia as well as using in vitro assays of virulence characteristics.…”

“…In S. pneumoniae , the effects of CS exposure on virulence are limited to the induction of biofilm formation and significant attenuation of the activity of pore-forming toxin pneumolysin ( ply) gene; [17, 18]. At the transcriptomic level, in vitro , acute CS exposure is reported to alter the expression of genes encoding factors required primarily for pneumococcal stress response and survival, as well as significantly downregulating ply expression without affecting the expression of other virulence genes [18, 19]. To date, the pathogenesis of CS-exposed pneumococci has not been examined in a mouse model of respiratory tract infection.…”