Author Correction: Baroreceptor denervation reduces inflammatory status but worsens cardiovascular collapse during systemic inflammation

An amendment to this paper has been published and can be accessed via a link at the top of the paper.


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Sepsis is a common disorder affecting 31.5 million people worldwide, with a 58 mortality rate of 5.3 million deaths every year (1). Considering the severity of sepsis in SAD + LPS (P > 0.9999) in comparison with Control + Sal animals (Fig. 2 C). 110 Spectral analysis in the frequency domain of the PI showed that LF power was 111 not significantly altered between Control + Sal, Control + LPS, SAD + Sal and SAD + 112 LPS groups (Fig. 3 A and C, P > 0.9999). Otherwise, HF power was significantly 113 reduced in Control + LPS (P < 0.0001) and in SAD + LPS rats (P < 0.0001) in relation 114 to Control + Sal group (Fig. 3 B and D). These results indicate that LPS administration 115 decreases cardiac vagal modulation in Control and SAD rats. Considering the SAP 116 spectral analysis, a significant increase in the LF component was observed in the 117 Control + LPS (P = 0.0051), but not in SAD + LPS (P > 0.9999) in relation to Control + 118 Sal group, indicating that LPS-induced increase in the sympathetic vasomotor 119 modulation depends on the baroreceptors afferents integrity (Fig. 3 B and E).

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The detrended fluctuation analysis (DFA α_2) scaling exponent was lower in 121 Control + LPS than in the Control + Sal group (P = 0.0223, Fig. 4 B), whereas the same 122 scaling exponent was significantly increased in SAD + Sal (P < 0.0001) and in SAD + 123 LPS (P = 0.0040) in relation to Control + Sal rats (Fig. 4 B). The DFA α_3 scaling 124 exponent was significantly higher in SAD + Sal (P = 0.0133) than in Control + Sal rats

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Considering our previous study that documented hemodynamic and 156 inflammatory changes 3 hours following LPS administration (18), cytokine levels were evaluated at this same period in plasma and spleen as an index of SI and the modulatory 158 role of sino-aortic afferents on the splenic anti-inflammatory reflex, respectively.     The present study is the first to report that baroreceptors afferents are key to 185 modulate not only LPS-induced SI but also its consequent cardiovascular changes and 186 to provide evidence that these phenomena are not dependent of each other. Supporting 187 this notion, we observed that the LPS-induced hypotension was higher and earlier in 188 rats previously submitted to SAD than in control rats. We also show that HF power of 189 PI was altered in rats that received LPS, while LPS-induced increase in LF component   In the search for mechanisms underlying hemodynamic control during SI, we 232 used spectral analysis of PI in the frequency domain, which showed that HF component 233 of PI was significantly reduced at 3 hours after endotoxin in Control + LPS and in SAD 234 + LPS in relation to Control + Sal (Fig 3 A and D). These observations are in line with 235 the concept that LPS-induced tachycardia is triggered by mechanisms resulting in a 236 decrease of vagal modulation to the heart (18). Significant changes in the autonomic 237 control to the heart have been observed during the initial phase of sepsis-associated SI 238 as a compensatory adjustment to avoid circulatory shock (29). Regarding the variance 239 of SAP in the frequency domain, the LF component was significantly increased in 240 Control + LPS rats than in Control + Sal and SAD + LPS (Fig. 3), indicating that LPS-  In addition to linear methods (time and frequency-domain analyses), non-linear 247 approaches were also used in the present study. Methods for analysis of nonlinear 248 dynamics has been utilized to increase the interpretation of the complexity 249 cardiovascular function (30,31). We found that DFA α_2 scaling exponent of SAP was 250 reduced in Control + LPS rats and was greater in SAD + Sal and in SAD + LPS than in 251 Control + Sal rats (Fig. 4). These findings are consistent with the notion that the control 252 of blood pressure is highly complex and that during LPS-induced SI the oscillations in 253 SAP tend to erratic or random patterns (α_2 < 1). In contrast, when LPS is 254 administrated to SAD animals, SAP oscillations tend to be smoother (α_2 > 1).

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Reconciling the data obtained from MSE curves, we observed that SAP entropy of the 256 SAD + Sal and Control + LPS was significantly different from those for Control + Sal 257 group (Fig. 5), suggesting the that the baroreflex plays an important role in the complex 258 11 response to challenges imposed to the cardiovascular system (30). Although a direct 259 interpretation of the functional meaning of these results is not an easy task, the analyses 260 of SAP complexity has been used to predict cardiovascular outcomes and has been 261 associated with high mortality risks (32). As far as we know, this is the first study that  (Fig. 6 and 7). have suggested that hypothermia is precisely controlled by specific mechanisms 299 mediated by the central nervous system (37). Based on these data, we suggest that 300 baroreceptor afferents integrity affect thermoregulatory control during SI by impairing a 301 key part of the afferent signals to the brain. We further speculate that among the The LPS-induced plasma surges of IL-6 (a pro-inflammatory cytokine) and IL-314 10 (an anti-inflammatory cytokine) in SAD rats were significantly reduced after SAD 315 (Fig. 6). These findings indicate that baroreflex does modulate the LPS-induced

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In addition to circulating macrophages aforementioned, the main efferent target 325 organ for the splenic anti-inflammatory reflex is the splenic macrophages located in the 326 white pulp (2). We showed here that spleen tissue homogenates collected from rats that submitted to SAD during LPS-induced SI (Fig. 8 B). Combining a previous study 331 showing that stimulation of the efferent fibers impinges upon the spleen leads to a 332 significant anti-inflammatory effects in this organ during LPS-induced SI (42) and our 333 14 own data in which SAD rats showed decreased LPS-induced surges of pro-334 inflammatory cytokines in the spleen, we suggest that the efferent arm of the splenic 335 anti-inflammatory reflex is modulated by baroreceptors afferents.

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Considering that baroreflex stimulation downregulates pro-inflammatory 337 cytokines in hypothalamus, but not in plasma, heart and spleen (19) we hypothesized 338 that SAD worsens cytokines surges in plasma. Contrary to our expectations, after SAD, 339 LPS-induced surges of cytokines were blunted in plasma and spleen (Fig 8.) suggesting  were not affected in SAD rats (Fig. 9 A). These data support the notion that during LPS-366 induced SI an increase in the hypothalamic-pituitary-adrenal axis activity occurs (44) 367 and that this activation is independent of the baroreceptor afferents integrity.

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To provide insights into the mechanisms involved in hypotension during SI, we 369 also assessed plasma NO (a potent vasodilator) and norepinephrine (a vasopressor 370 neurotransmitter) levels (Figs 9). Taking into consideration that during sepsis, NO 371 pathway system is markedly stimulated leading to decreased vascular responsiveness to 372 constrictor stimuli (22), our findings further support the notion that indeed LPS-induced 373 SI is accompanied by a significant increase in plasma NO production, that does not 374 depend on baroreceptors integrity. Moreover, these findings indicate that greater 375 hypotension in SAD rats is not associated with higher NO production, but rather to the 376 autonomic imbalance per se (Fig. 9 B). Siminarly, the observed effects of SAD on the 377 LPS-induced hemodynamic dysfunction seems to be independent of systemic 378 noradrenaline levels, since this catecholamine levels were similar among groups (Fig. 9 379 C). However, these data do not rule out that local noradrenaline release from 380 sympathetic nerve terminals during SI may be different depending on the vascular bed.

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In conclusion, the present data are consistent with the notion that the role of  Calgary, AB, Canada) was inserted to deep body (Tb) temperature recordings in rats. 458 Afterward, surgical wounds were sutured aseptically.

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Vascular reactivity studies 460 The method described by Mulvany and Halpern (1977)     Rats were assigned into 4 experimental groups: 512 Control + Sal: Naïve rats that received saline administration. 513 Control + LPS: Naïve rats that received LPS administration. 514 SAD + Sal: SAD rats that received saline administration. 515 SAD + LPS: SAD rats that received LPS administration.    Data are expressed as mean ± S.E.M. (standard error of the mean) and 536 significant differences were considered at P ≤ 0.05, but exact P values are described.

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Unpaired t test, one-, two-way ANOVA followed by the Bonferroni multiple 538 comparisons test or Kruskal-Wallis test followed by Dunn's multiple comparisons test 539 were performed when necessary.