Effects of the recombinant crustacean hyperglycemic hormones rCHH-B1 and rCHH-B2 on the osmo-ionic regulation of the shrimp Litopenaeus vannamei exposed to acute salinity stress

Abstract

The Pacific white shrimp Litopenaeus vannamei is a euryhaline organism that copes with salinity fluctuations in the environment; therefore, its osmotic and ionic regulation abilities are vital. Osmoregulation may be controlled by the crustacean hyperglycemic hormone (CHH), a neuropeptide mainly expressed in the eyestalks. In L. vannamei, CHH-B1 and CHH-B2 are CHH isoforms isolated from the eyestalks whose expression is influenced by environmental salinity. It has been suggested that they are involved in the response to salinity stress. To clarify this, we investigated the effect of the recombinant peptides, rCHH-B1 and rCHH-B2, on the osmo-ionic regulation of shrimp acutely exposed to different salinity conditions (8, 26 and 45‰). Both rCHHs promoted differential effects on the osmoregulatory capacity (OC) and the ionoregulatory capacity (IC) for hemolymph Na and Cl during iso-osmotic (26‰) and hyper-osmotic (45‰) transfers. These changes were linked to the changes observed in Na/K ATPase and carbonic anhydrase gene expression in gills, especially under high salinity conditions, suggesting that the hormones may regulate the expression of these genes. Glucose and protein levels measured during acute salinity transfer suggest their roles as sources of metabolic energy for osmotic regulation or as organic osmolytes. These results taken together suggest that both the CHH-B1 and CHH-B2 peptides are important regulators of the physiological response of L. vannamei to acute salinity fluctuations.

Effect of recombinant crustacean hyperglycemic hormones rCHH‐B1 and rCHH‐B2 on lipid metabolism in the Pacific white shrimp Litopenaeus vannamei

“…In the present work, a significant increase in haemolymph glucose levels (40%–60%) was observed at 0.5 hr and 1 hr post‐injection of rCHH‐B2 in comparison with the rCHH‐B1 levels. A higher hyperglycemic activity has also been obtained with the rCHH‐B2 during isosmotic conditions (26 ppm), but not on the shrimp acutely exposed to hypo‐osmotic (8 ppm) or hyper‐osmotic salinities (45 ppm) (Camacho‐Jiménez et al., 2018). Furthermore, glucose analysis of haemolymph of shrimp injected with dopamine (DA) suggested that the hyperglycemic effect of DA is mediated by the release of CHH neuropeptides from the eyestalk of L. vannamei (Camacho‐Jiménez, Díaz, et al, 2017).…”

“…The functional diversity of CHHs has been related to variants differing in sequence and structures within species (Lee et al., 2014). Three different CHH variants have been cloned and sequenced by our group from the Pacific white shrimp L. vannamei : CHH‐A, CHH‐B1 and CHH‐B2 (Camacho‐Jiménez et al., 2015, 2018; Camacho‐Jiménez, Sánchez‐Castrejón, et al, 2017; Lago‐Lestón et al., 2007; Sanchez‐Castrejón, Ponce‐Rivas, Aguilar, & Díaz, 2008). Additionally, a new gene containing four exons and three introns was isolated from L. vannamei (Ventura‐López et al., 2016).…”

“…In L. vannamei, vital processes such as carbohydrate metabolism and osmoregulation were affected by rCHH‐B1 and rCHH‐B2 variants (Camacho‐Jiménez et al, 2018; Camacho‐Jiménez, Sánchez‐Castrejón, et al, 2017; Camacho‐Jiménez et al., 2015; Sanchez‐Castrejón et al, 2008). The dose–response assays realized for rCHH‐B1 (Camacho‐Jiménez et al., 2015) and rCHH‐B2‐Gly (Camacho‐Jiménez, Sánchez‐Castrejón, et al, 2017) showed that the hyperglycemic effect is dependent of the dosage of the hormones.…”

“…Furthermore, glucose analysis of haemolymph of shrimp injected with dopamine (DA) suggested that the hyperglycemic effect of DA is mediated by the release of CHH neuropeptides from the eyestalk of L. vannamei (Camacho‐Jiménez, Díaz, et al, 2017). rCHH‐B1 and rCHH‐B2 also promoted differential effects on the OC of haemolymph and in Na + /K + ATPase gene expression in gills of shrimp acutely exposed to different salinity conditions (Camacho‐Jiménez et al., 2018). Because glucose levels are increased in shrimp haemolymph by rCHH‐B1 and rCHH‐B2 injection, it appears that they have a role in providing a source of metabolic energy for osmotic regulation.…”

“…Of the L. vannamei CHH variants described by our group (CHH‐A, CHH‐B1 and CHH‐B2), CHH‐B1 and CHH‐B2 are very interesting since they are produced by alternative splicing of one gene ( chhB ) (Camacho‐Jiménez, Díaz, et al, 2017; Camacho‐Jiménez, Sánchez‐Castrejón, et al, 2017; Lago‐Lestón, Ponce, & Muñoz, 2007). Both variants have hyperglycemic activity and are involved in osmoregulatory capacity (OC) and hydro‐mineral balance in L. vannamei (Camacho‐Jiménez, Díaz, et al, 2017; Camacho‐Jiménez, Sánchez‐Castrejón, et al, 2017; Camacho‐Jiménez, Díaz, Sánchez‐Castrejón, & Ponce‐Rivas, 2018). CHH‐B2 also presents a dose‐dependent effect on triglyceride concentration in L. vannamei haemolymph (Camacho‐Jiménez, Sánchez‐Castrejón, et al, 2017).…”