Hi Jesus, thank you for the nice presentation, I saw your work at SFRR-I as well, I think it is really interesting. I was wondering how you isolated the histones, and whether any specific histones were more potent at having the effect. I saw from the lecture earlier that H3 and H2B correlate in sepsis patients, but I wasn’t sure if these were the most reactive biologically?
Also, I wondered more broadly, whether the DNA component of the NETs could have any role in sepsis? The results seem mixed in the literature, in some studies I’ve read where DNase is used to digest the DNA of the NETs.
Hi Clare, thanks for the question. Our group has developed a protocol for the extraction and purification of histones from animal and human cells, and also from tissues, serum, and plasma. I can send you the different protocols if you need them.
Regarding the role of individual histones, it is true that H2B and H3 correlate very well with the diagnosis and prognosis of sepsis, and that is why we have developed the patent around these two histones, but it is rather methodological. In fact, the only histone that has been shown to have a less cytotoxic effect is H1, the rest of the histones, H2A, H2B, H3, and H4 have different cytotoxicities, depending on the cell type, but all of them are highly cytotoxic. However, interestingly, H1 does not have a cytotoxic effect in most cell types, but it does have a very high cytotoxic effect (higher than the rest of histones) in different brain cell types. Therefore, we can conclude that the reactivity of each type of histones largely depends on the cell type to which they are exposed.
Regarding DNA and sepsis, during the NETosis process, as well as other types of etosis, and even the cell death that occurs during an episode of sepsis, DNA is widely spread and seems to have a cytotoxic capacity, although apparently, its degradation is easier, so it is usually found at lower levels than histones, or nucleosomes, for example. However, DNA has a relevant role in NETs-mediated cytotoxicity, and in most cases, higher than the rest of the nuclear proteins that make them up, although as you said, all this is not too much clear, and much more data is needed to clarify it.
This is my e-mail: email@example.com. If you have any questions or I can help you with something, don’t doubt to mail me.
One other thing, the effect of acetylation – what is the pathway? A charge effect if Lys is modified?
Hello again Clare. We think that the cytotoxicity of histones could be due to changes in membrane potential because of the nature of histones (they are very basic). Therefore, acetylation as PTM of Histones could be playing a key role in reducing histone positivity and, as we have demonstrated, in membrane potential, which in turn leads to the induction of pyroptosis and would explain the reduction in cell death. However, the exact mechanism through which acetylated histones are less harmful is not fully understood yet, and we are continuing to work on it.
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