Nucleated Fish Erythrocyte Extracellular Traps (FEETs) release is an evolutionary conserved immune defence process

Fish erythrocytes remain nucleated for their life-span, unlike mammalian erythrocytes which undergo enucleation. Asides transportation of oxygen, fish erythrocytes are capable of several immune defence processes. Nucleated fish erythrocytes represent prime candidates for carrying out ETotic responses. ETosis is an evolutionary conserved innate immune defence process found in both vertebrates and invertebrates, which involves the extrusion of DNA studded with antimicrobial proteins into the extracellular space serving to trap and kill microorganisms. In this report, we demonstrate that fish erythrocytes isolated from Danio rerio (zebrafish) produce ETotic-like responses when exposed to chemical and physiological stimuli. Salmo salar (Atlantic salmon) erythrocytes produce similar ETotic responses. We have termed these ET-like formations Fish Erythrocyte Extracellular Traps (FEETs). Interestingly, we discovered that mammalian inducers of NETosis, such as the protein kinase C (PKC) activator phorbol 12‐myristate 13‐acetate and the calcium ionophore ionomycin induced FEETs. Moreover, we found that FEETs are dependent upon activation of PKC and generation of mitochondrial reactive oxygen species. Thus, this brief report represents the first demonstration that fish erythrocytes can exhibit ETotic-like responses, unveiling a previously unknown function of nucleated erythrocytes, and sheds new light on the innate immune arsenal of erythrocytes.

ОСОБЛИВОСТІ ОСМОТИЧНОЇ РЕЗИСТЕНТНОСТІ ЕРИТРОЦИТІВ ТА ВМІСТУ ГЕМОГЛОБІНУ У КРОВІ РИБ ЗА ДІЇ ФЕРУМУ (III)

The osmotic resistance of erythrocytes and the content of hemoglobin in the blood of carp (Cyprinus carpio L.) and pike (Esox lucius L.) under the action of Fe3+ ions at concentrations of 0.2 and 0.5 mg/dm3, were under study which corresponded to 2 and 5 maximum permissible concentration (MPC). The research demonstrated that increased concentrations of Fe3+ ions lead to changes in the osmotic resistance of erythrocytes and the content of hemoglobin in the blood of carp and pike. The findings suggest that high concentrations of Iron (5 MPC) in carp lead to a decrease in the resistance of erythrocyte membranes, and in pike it led to increased osmotic resistance of erythrocytes, which is apparently due to different mechanisms of adaptation of fish erythrocyte membranes to adverse aquatic environment. Species-specificity is also characterized by changes in the content of hemoglobin in the blood of fish species which were researched. An increased amount of pigment in the blood of carp and a decreased amount of hemoglobin in pike under the action of 5 MPC of metal ions was established. The obtained results can be used to assess the physiological condition of fish and water quality under conditions of contamination of watercourses with metals.

Association of the band 3 protein with a volume-activated, anion and amino acid channel: a molecular approach.

In response to swelling, cells recover their initial volume by releasing intracellular solutes via volume-sensitive pathways. There is increasing evidence that structurally dissimilar organic osmolytes (amino acids, polyols, methyl amines), which are lost from cells in response to swelling, share a single pathway having the characteristics of an anion channel. However, the molecular identity of this pathway remains to be established. It has been suggested that the erythrocyte anion exchanger (AE1) or some AE1-related proteins could be involved. A direct evaluation of this possibility has been made by comparing the functional properties of two AE1s when expressed in Xenopus laevis oocytes: tAE1 is from a fish erythrocyte which releases taurine when swollen, and mAE1 is from a mammalian erythrocyte which does not regulate its volume when swollen. While mAE1 performs exclusively Cl-/Cl- exchange, tAE1 behaves as a bifunctional protein with both anion exchange and Cl-/taurine channel functions. Construction of diverse tAE1/mAE1 chimaeras allows the identification of protein domains associated with this channel activity. Thus, some AE1 isoforms could act as a swelling-activated osmolyte channel, a result having a potentially important implication in malaria. This review also discusses the possibility that several different proteins might function as swelling-activated osmolyte channels.

Histone proteolysis in fish erythrocyte nuclei

The erythrocyte histones of trout, carp, white sucker, and chicken are subject to very different levels of autolytic activity. Carp erythrocyte histones extracted from typical nuclear preparations suffer extensively from degradation; histones 1, 5, and 3 (H1, H5, and H3 respectively) are preferentially cleaved and characteristic peptides designated P1, P2, and P3 appear during the course of proteolysis. Generally, erythrocytes from different fish species yield highly disparate proportions of H1 and H5, but this is not a consequence of the variable levels of proteolytic activity in these species.Phenylmethylsulfonyl fluoride (PMSF) (1.0 mM) was found to be superior to 50 mM sodium bisulfite as a protease inhibitor and was well suited for use in media employed for cell washes and the isolation of nuclei. Nonetheless, in carp erythrocytes residual protease activity (qualitatively the same as the uninhibited activity) persists even in the presence of PMSF. It is activated during cell lysis and remains associated with the nuclear fraction of the lysate during subsequent washes. The isolation of intact nuclei is important for the ultimate extraction of undegraded histone, especially from sources in which the risks of autolysis are high or unknown.