# Role of Liver Kinase 1B in Platelet Activation and Host Defense During Klebsiella pneumoniae-Induced Pneumosepsis

## TL;DR

This study investigates how Liver Kinase B1 (LKB1) affects platelet function and immune response during sepsis caused by Klebsiella pneumoniae.

## Contribution

The study reveals that LKB1 regulates platelet activation in response to GPVI stimulation but does not significantly affect host defense during pneumosepsis.

## Key findings

- LKB1-deficient platelets showed hyperreactivity to GPVI stimulation in naive mice.
- During K. pneumoniae infection, platelets from both LKB1-deficient and control mice became equally hyporesponsive to GPVI stimulation.
- LKB1 deficiency did not alter bacterial spread, inflammation, or lung damage during pneumosepsis.

## Abstract

Pneumonia is the most common cause of sepsis, with Klebsiella pneumoniae frequently implicated as a causative pathogen. Platelets play a crucial role in host defense during sepsis, and their activation is essential for effective immune responses, which is at least in part induced through activation of the collagen receptor glycoprotein (GP)VI. Platelets require energy for their activation, and Liver kinase B1 (LKB1) is a key regulator of energy metabolism. We sought to determine the role of LKB1 in platelet function and host response during K. pneumoniae-induced pneumosepsis. Platelet-specific-Lkb1-deficient mice were generated and compared to control littermates. Platelet counts were unaffected by Lkb1 deficiency in naïve mice. However, Lkb1-deficient platelets exhibited significant hyperreactivity to GPVI stimulation, an effect not observed after stimulation of the thrombin receptor protease-activated receptor 4. During K. pneumoniae infection, platelets of both Lkb1-deficient and control mice became equally hyporesponsive to GPVI stimulation, without differences between genotypes. Platelet-specific Lkb1 deficiency did not alter bacterial outgrowth or dissemination, inflammatory responses, or lung pathology. These findings suggest that while Lkb1 plays a role in regulating platelet activation in response to GPVI stimulation, it does not significantly impact platelet activation or the host response during pneumonia-induced sepsis.