Expression of apoptosis-related genes in the mouse skin during the first postnatal catagen stage, focused on localization of Bnip3L and caspase-12

Exploring caspase functions in mouse models

Caspases are enzymes with protease activity. Despite being known for more than three decades, caspase investigation still yields surprising and fascinating information. Initially associated with cell death and inflammation, their functions have gradually been revealed to extend beyond, targeting pathways such as cell proliferation, migration, and differentiation. These processes are also associated with disease mechanisms, positioning caspases as potential targets for numerous pathologies including inflammatory, neurological, metabolic, or oncological conditions. While in vitro studies play a crucial role in elucidating molecular pathways, they lack the context of the body's complexity. Therefore, laboratory animals are an indispensable part of successfully understanding and applying caspase networks. This paper aims to summarize and discuss recent knowledge, understanding, and challenges in caspase knock-out mice.

Making the head: Caspases in life and death

The term apoptosis, as a way of programmed cell death, was coined a half century ago and since its discovery the process has been extensively investigated. The anatomy and physiology of the head are complex and thus apoptosis has mostly been followed in separate structures, tissues or cell types. This review aims to provide a comprehensive overview of recent knowledge concerning apoptosis-related molecules involved in the development of structures of head with a particular focus on caspases, cysteine proteases having a key position in apoptotic pathways. Since many classical apoptosis-related molecules, including caspases, are emerging in several non-apoptotic processes, these were also considered. The largest organ of the head region is the brain and its development has been extensively investigated, including the roles of apoptosis and related molecules. Neurogenesis research also includes sensory organs such as the eye and ear, efferent nervous system and associated muscles and glands. Caspases have been also associated with normal function of the skin and hair follicles. Regarding mineralised tissues within craniofacial morphogenesis, apoptosis in bones has been of interest along with palate fusion and tooth development. Finally, the role of apoptosis and caspases in angiogenesis, necessary for any tissue/organ development and maintenance/homeostasis, are discussed. Additionally, this review points to abnormalities of development resulting from improper expression/activation of apoptosis-related molecules.

Caspase-12 Is Present During Craniofacial Development and Participates in Regulation of Osteogenic Markers

Caspases are evolutionary conserved proteases traditionally known as participating in apoptosis and inflammation but recently discovered also in association with other processes such as proliferation or differentiation. This investigation focuses on caspase-12, ranked among inflammatory caspases but displaying other, not yet defined functions. A screening analysis pointed to statistically significant (P < 0.001) increase in expression of caspase-12 in a decisive period of mandibular bone formation when the original mesenchymal condensation turns into vascularized bone tissue. Immunofluorescence analysis confirmed the presence of caspase-12 protein in osteoblasts. Therefore, the osteoblastic cell line MC3T3-E1 was challenged to investigate any impact of caspase-12 on the osteogenic pathways. Pharmacological inhibition of caspase-12 in MC3T3-E1 cells caused a statistically significant decrease in expression of some major osteogenic genes, including those for alkaline phosphatase, osteocalcin and Phex. This downregulation was further confirmed by an alkaline phosphatase activity assay and by a siRNA inhibition approach. Altogether, this study demonstrates caspase-12 expression and points to its unknown physiological engagement in bone cells during the course of craniofacial development.

Potential Roles of NIX/BNIP3L Pathway in Rat Traumatic Brain Injury

NIX/BNIP3L is known as a proapoptotic protein that is also related to mitophagy. Previous reports have shown that NIX could be involved in neuronal apoptosis after intracerebral hemorrhage, but it also plays a protective role in mitophagy in ischemic brain injury. How NIX works in traumatic brain injury (TBI) is unclear. Thus, this study was designed to observe the expression of NIX and perform a preliminary exploration of the possible effects of NIX in a rat TBI model. The results showed that NIX expression decreased after damage, and colocalized with neuronal cells in cortical areas. Moreover, when we induced upregulation of NIX, autophagy was increased, while neuronal apoptosis and brain water content decreased along with neurological deficits. These findings remind us that NIX probably plays a neuroprotective role in TBI through autophagy and apoptosis pathways.

Non-apoptotic role for caspase-7 in hair follicles and the surrounding tissue

Hair follicles are unique organs undergoing regular cycles of proliferation, differentiation, and apoptosis. The final step of apoptosis is, in general, mediated by executioner caspases comprising caspase-3, -6 and -7. Despite their commonly accepted apoptotic function, executioner caspases also participate in non-apoptotic processes. In the present study, we investigated activation (cleavage) of caspase-7 in mouse hair follicles and surrounding tissue during embryonic development into adulthood. Casp7 (-/-) mice were examined to understand the effect of caspase-7 deficiency in the skin. The activated form of caspase-7 was observed during embryonic hair follicle development, as well as in the first hair cycle. In general, activation of caspase-7 did not correlate with apoptosis and activation of caspase-3, except during physiological hair follicle regression. Notably, cleaved caspase-7 was observed in mast cells and its deficiency in the adult skin resulted in increased mast cell number. Our study shows for the first time activated caspase-7 in hair follicles and mast cells and indicates its non-apoptotic roles in the skin.